composite materials (1)

Composite Materials

Prof. Alleson Herman V. Corey

M. Sc. Polymer and Composites Engineering

Cum Fructo

Katholieke Universiteit Leuven (Belgium)

B. Sc. Mechanical Engineering

Cum Laude

Central Mindanao University (Philippines)

Condensed Book Series by Prof. A.H.V. COREY

Dedication

� This Condensed Book Series is dedicated

to:

� The Almighty GOD (God the Father, God the Son

Jesus Christ, and God the Holy Spirit).

� My Wife Ninnin, my Son Elgien, and my Daughter

Sheanne.

Introduction to Composite

Materials



Cum Fructo



Cum Laude


Composite Material� any combination of two or more different materials

at the macroscopic level, in a controlled manner to give desired properties. The properties of a composite will be different from those of the constituents in isolation.

� Two or more chemically distinct materials which when combined have improved properties over the individual materials.

� A judicious (good sense) combination of two or more materials that produces a synergistic(combined) effect. A material system composed of two or more physically distinct phases whose combination produces aggregate (combined) properties that are different from those of its constituents.

Composite Material� A material with two (or more) distinct

macroscopical phases. They consist of two or more materials combined in such a way that the individual materials are easily distinguishable.

� A common example of a composite is a concrete.

Composite Material

� A combination of two or more materials (reinforcement, resin, filler, etc.), differing in form or composition on a macroscale (visible). The constituents retain their identities, i.e., they do not dissolve or merge into each other, although they act in concert (together). Normally, the components can be physically identified and exhibit an interface (distinct phase) between each other.

� A structural material that consists of two or more combined constituents that are combined at a macroscopic level and are not soluble in each other.� Reinforcing phase: fibers, particles, or flakes

� Matrix phase: polymers, metals, ceramics

Composite Material

� A material composed of 2 or more

constituents.

� Two inherently different materials that when

combined together produce a material with

properties that exceed the constituent

materials.

� Reinforcement phase (e.g., Fibers)

� Matrix or Binder phase (e.g., compliant or compatible matrix)

Silver – Copper Alloy reinforced with Carbon

Fibers.

In Borsic fiber-reinforced aluminum, the fibers are

composed of a thick layer of boron deposited on a small –diameter tungsten filament.

Composite Material (cross-section)

Composite Material (cross-section)

Composite Material (concept)

Concept:

� Using the high strength of fibers to stiffen and strengthen a cheap matrix material.

� The load is applied over a large surface area of the matrix. Matrix then transfers the load to the reinforcement, which being stiffer, increases the strength of the composite. It is important to note that there are many matrix materials and even more fiber types, which can be combined in countless ways to produce just the desired properties.

Composite Material (concept)� Composite materials are like

sandwiches. A good sandwich

contains a variety of ingredients to

yield a taste that no single ingredient

could provide by itself.

� Similarly, composite materials are

those which are formed from two or

more materials producing properties or

characteristics that could not be

obtained from any one material.

� Composites consist of one or more

discontinuous phases fixed in a

continuous phase. The discontinuous

phase is usually harder and stronger

than the continuous phase and is

called the reinforcement or reinforcing

material, whereas the continuous

phase is termed the matrix.

Composite Material (facts)Some Facts:

� The composite industry is new and has grown rapidly in the past 30 years with the development of “fibrous composites”.

� In the United States, composites manufacturing is a 25 billion dollar a year industry. There are about 6,000 composites related manufacturing plants and materials distributors across the U.S. The industry employs more than 235,000 people. An additional 250,000 people are employed in businesses that support the composites industry, including materials suppliers, equipment vendors, and other support personnel.

� About 90% of all composites produced are comprised of glass fiber (reinforcement) and either polyester or vinyl-ester resin (matrix) and are known as reinforced plastics.

Composite Material (Advantages)� Very light materials (light weight)

� High strength and stiffness (rigidity)

� Low weight to strength ratio

� Material can be designed in addition to the structure

� Design flexibility

� Composites have an advantage over other materials because they can be molded into different or complex shapes and size at relatively low cost. This gives designers the freedom to create any shape or configuration. Boatsare a good example of the success of composites.

� Corrosion Resistance

� Composites products provide long-term resistance to severe chemical, temperature, and weathering environments. Composites are the material of choice for outdoor exposure, chemical handling applications, and severe environment service.

Composite Material (Advantages)� Durability (Low Maintenance / Long Term Life)

� Composite products and structures have an exceedingly long life span. Coupled with low maintenance requirements, the longevity of composites is a benefit in critical applications. In a half-century of composites development, well-designed composite structures have not yet to wear out (extended service life).

� FACT: In 1947 the U.S. Coast Guard built a series of forty-foot patrol boats, using polyester resin and glass fiber. These boats were used until the early 1970’s when they were taken out of service because the design was outdated. Extensive testing was done on the laminates after decommissioning, and it was found that only 2-3% of the original strength was lost after twenty-five years of hard service.

� Dimensional Stability (stable shape even at elevated temperature)

Composite Material (Advantages)� High specific strength and modulus, as well as high

fatigue strength and fatigue damage tolerance.

� Orientated Strength (base on reinforcement direction)

� Low Thermal Conductivity

� Other unique functional properties - damping, low CTE (coefficient of thermal expansion)

� Consolidation of Parts - can manufacture structures and eliminate joints

� Large Part Size Possible to manufacture - production of both material and structure or component in a single operation - manufacturing flexible, net-shape, complex geometry (shape).

� Designable or tailorable materials for both microstructure (reinforcement structure), mechanical properties and aesthetic (beauty) appearance

Composite Material (Advantages)� Composites have a

higher specific strength (strength to weight ratio) than many other materials.

� A distinct advantage of composites over other materials is the ability to use many combinations of resins and reinforcements, and therefore custom tailor (design according) to the required mechanical and physical properties of a structure.

Composite Material (Advantages)� The low properties

composite material are associated with simple

manufacturingprocesses and material forms (e.g. spray lay- up glass fibre), while the higher properties are associated with higher technology manufacturing process(e.g. autoclave moulding of unidirectional glass

fibre) and usually applied in the Aerospace (Aircraft) Industry.

Composite Material (Disadvantages)� Composites are heterogeneous (compose of different

material components)� Properties in composites vary from point to point in the

material. Most engineering structural materials arehomogeneous.

� Composites are highly anisotropic� The strength in composites vary as the direction along

which we measure changes (most engineering structural materials are isotropic). As a result, all other properties such as, stiffness, thermal expansion, thermal and electrical conductivity and creep resistance are also anisotropic. The relationship between stress and strain(force and deformation) is much more complicated than in isotropic materials.

� NOTE: The experience and intuition (something already known) gained over the years about the behavior of metallic materials does not apply to composite materials.

Composite Material (Disadvantages)

� Mechanical property characterization (determination) of a composite structure is more complex than a metal structure (since composite is a combination of 2 or more materials).

� High production (manufacturing / fabrication) cost.

� Difficult to repair - repair process is not simple compared to metals.

� Susceptible to damage.


� Do not have

a high

combination

of strength

and fracture

toughness

compared to

metals.


� Do not give higher

performance in all

the properties used

for material selection:

strength, toughness,

formability, joinability,

corrosion resistance,

and affordability.

Composite Material (Disadvantages)� Composites materials are difficult to inspect with

conventional ultrasonic, eddy current and visual NDI methods such as radiography.

FACT: American Airlines Flight

587, broke apart over New York on

Nov. 12, 2001 (265 people died).

Airbus A300’s 27-foot-high tail fin

tore off. Much of the tail fin,

including the so-called tongues that

fit in grooves on the fuselage and

connect the tail to the jet, were

made of a graphite composite. The

plane crashed because of damage

at the base of the tail that had gone

undetected despite routine

nondestructive testing and visual

inspections.


� FACT: In November 1999, America’s Cup boat “Young

America” broke in two due to debonding face/core in the sandwich structure.

Composite Material (Economics)

� Material costs -- higher for composites

� Constituent materials (e.g., fibers and resin)

� Processing costs -- embedding fibers in matrix

� not required for metals Carbon fibers order of magnitude

higher than aluminum

� Design costs -- lower for composites

� Can reduce the number of parts in a complex assembly by designing the material in combination with the structure

� Increased performance must justify higher material costs

� Low Relative Investment

� One reason the composites industry has been successful is because of the low relative investment in setting-up a composites manufacturing facility. This has resulted in many creative and innovative companies in the field.

Composite Material (2 Main Types)

Composites can be broadly classified in to two groups:

� Natural

� Synthetic (Man-made)

Examples:

� Natural Composite:� Wood is a good example of a natural composite,

combination of cellulose fiber and lignin. The cellulose fiber provides strength and the lignin is the "glue" that bonds and stabilizes the fiber.

� Bamboo is a very efficient wood composite structure. The components are cellulose and lignin, as in all other wood, however bamboo is hollow. This results in a very light yet stiff structure. Composite fishing poles and golf club shafts copy this natural design.

� Bone, Muscle, Fish fins

Composite Material (2 Main Types)

� Synthetic (Man-made) Composite - produced by combining two or more materials in definite proportions under controlled conditions.� The ancient Egyptians manufactured composites!

Adobe bricks are a good example. The combination of mud and straw forms a composite that is stronger than either the mud or the straw by itself.

� Ferro-cement

� Plywood, Chipboards, Decorative laminates

� Asbestos Cement Sheets

� Fiber Reinforced Plastic (FRP) or Polymer Matrix Composite (PMC)

Composite Material (Basic Types)� 5 Basic Types of Composite Materials (base on

reinforcement shape): Fiber (continuous or long), Particle(small size), Flake (big size particle), Laminar (Laminate or layered), and Filled (short fibers or Whiskers) composites.

Reinforcement Composite

Composite Material (Basic Types)

� Particulate composites

� Flake composites

� Fiber composites

� Nano composites –

nano-particles (metals,

oxides, compounds),

nano-flakes, or nano-

fibers (nano-wires) of

very small dimension

or diameter (1-100 nm)

Composite Material (Sample Fibers)

(Long / Continuous Fiber)

(Short Fibers, Random orientation)

(SMC – Sheet Molding Compound)

(usually Glass Fibers)

(Aligned)

Composite Material (Classification)Matrix Phase /

Reinforcement

Phase

Metal Ceramic Polymer

Metal

Powder metallurgy

parts – combining

immiscible metals

Cermets

(ceramic-metal

composite)Brake pads

Ceramic

Cermets, TiC,

TiCN Cemented

carbides – used in

tools Fiber -

reinforced metals

SiC reinforced

Al2O3

Tool materials

Fiberglass

Polymer Kevlar fibers in

an epoxy matrix

Elemental

(Carbon,

Boron, etc.)

Fiber reinforced

metals for

Auto parts and

aerospace

Rubber with

carbon (tires)

Boron, Carbon

reinforced plastics

MMC’s CMC’s PMC’sMetal Matrix Composites Ceramic Matrix Composites Polymer Matrix Composites

Composite Material (Classification)� Metal Matrix Composites (MMC’s)

� Include mixtures of ceramics and metals, such as cemented carbides and other cermets, as well as

aluminum or magnesium as matrix material then

reinforced by strong, high stiffness fibers.

� Ceramic Matrix Composites (CMC’s)

� Least common composite matrix. Aluminum oxide

and silicon carbide are matrix materials that can be

imbedded with fibers for improved properties,

especially in high temperature applications.

� Polymer Matrix Composites (PMC’s)

� Thermosetting resins are the most widely used

polymers as matrix in PMC’s. Epoxy and polyester are

commonly mixed with fiber reinforcement.

Composite Material (Classification)

Large-

particle

Dispersion-

strengthened

Particle-reinforced

Continuous

(aligned)

Aligned Randomly

oriented

Discontinuous

(short)

Fiber-reinforced

Laminates Sandwich

panels

Structural

Composites

MMC, CMC, PMC

Composite Material (composition)

A composite material consists of two phases:

� Primary (Matrix)

� Forms the matrix within which the secondary phase is imbedded

� Any of three basic material types: polymers, metals, or ceramics

� Secondary (Reinforcement)

� Referred to as the imbedded phase or called the reinforcing agent

� Serves to strengthen the composite. (fibers, particles, etc.)

� Can be one of the three basic materials or an element such as carbon or boron


� Composites are combinations of two materials in which one of the material is called the reinforcing phase in the form of fibers, sheets (flakes), or particles, and is embedded in the other material called the matrix phase.

� Reinforcing materials are strong with low densitieswhile the matrix material is usually a ductile or tough.

NOTE: Composite properties are less than that of the fiber because of dilution (less concentrated or weakened due to mixture) by the matrix and the need to orient fibers in different directions.


� Example:

� Glass Reinforcing material (Reinforcing phase)

� Polyester material (Matrix phase)

� Result: Glass + Polyester = GRP (Glass-Fiber Reinforced Plastic)

NOTE: If the composite is designed and fabricated correctly, it combines the strength of the reinforcement with the toughness of the matrix to achieve a combination of desirable properties not available in any single conventional material.


Components of composite materials

� Reinforcement fibers

� Glass, Carbon, Organic, Boron, Ceramic, Metallic

� Matrix materials

� Polymers, Metals, Ceramics

� Interface - Bonding surface

• Composites:-- Multiphase material with significant

proportions of each phase.

• Dispersed phase (Reinforcement):-- Purpose: enhance matrix properties.

MMC: increase σy, TS, creep resist.CMC: increase Kc

PMC: increase E, σy, TS, creep resist.

-- Classification: Particle, Fiber, Structural

• Matrix:-- The continuous phase-- Purpose:

- transfer stress to other phases

- protect phases from environment

-- Classification: MMC, CMC, PMC

metal ceramic polymer

Terminology/Classification woven fibers

cross section view

0.5 mm

0.5 mm

TS = tensile stress

Kc = thermal conductivity

Matrix (Functions)

� Functions of the Matrix� Bonds with the fibers (Very important).

� Separate the fibers.

� Transmit force (stresses) between fibers� Arrest (stop) cracks from spreading between fibers

� Fibers do not carry most of the load some are shared by the Matrix.

� Hold fibers in proper orientation

� Protect fibers from environment� mechanical forces can cause cracks that allow

environment to affect fibers

� Protect fibers from surface damage due to abrasion or corrosion (i.e., avoid cracks on surfaces of fibers).

Matrix (Demands)

� Demands on Matrix (design consideration)

� Interlaminar (from one lamina to the next lamina) shear strength

� Toughness (resistance to breaking)

� Ductility

� Moisture / environmental resistance

� Adhesion (bonding) to reinforcement

� Temperature properties (important for application environment / condition, heat resistance)

� Processing (manufacturing) Method – complexity (simple or complex) and equipments

� Production (manufacturing) Cost

Matrix (Types – Metal and Ceramic)� Metal Matrix materials - higher temperature

application

� Aluminum (matrix) with boron or carbon fibers

� Aluminum-Lithium, Magnesium, and Titanium as matrix materials. The fibers used are graphite (carbon fibers), aluminum-oxide, silicon carbide, and boron.

� Ceramic Matrix materials - very high temperature application

� Silicon carbide, Silicon nitride, Aluminum oxide, and Mullite as matrix materials. The fibers used are various (different kinds) ceramics.

� Fiber is used to add toughness (resistance to breaking) to ceramic matrix, not necessarily higher (little effect) in strength and stiffness (ceramic material is already strong and stiff).

Matrix (Types – Polymer)

� Thermoplastics� Formed (shaped) by heating to elevated (high)

temperature at which softening occurs.� Reversible reaction (soften or harden and vice-versa).

� Can be reformed (re-shape) and / or repaired.

� Limited in temperature (application) range up to 150OC.

� Examples:

� Polypropylene (PP)� with nylon or glass (reinforcement).

� PP can be injected – inexpensive (cheaper manufacturing process since few equipment materials needed).

� Soften layers (by heating) of combined fiber and PP then place in a mold -- higher costs (more equipment materials needed).


� Thermoplastics

� Examples:

� Polyetheretherketone (PEEK)

� Tougher (resistance to breaking) than Thermosets but lower resistance to temperature (less than 150OC

temperature application).

� Fibers used:

� Glass, Aramid (kevlar), Carbon (graphite), and Boron

Matrix (Types – Polymer)� Thermosets

� Cure (to finish) by chemical reaction (harden)� Heated in oven (autoclave) at more than 100OC

� Irreversible

� Examples:

� Polyester and Vinylester

� Most common, lower cost, solvent resistance.

� Polyesters have good mechanical properties, electrical properties and chemical resistance. They are amenable (required) to multiple fabrication techniques and are low cost.

� Vinyl Esters are similar to polyester in performance and have increased (better) resistance to corrosive environments as well as a high degree of moisture resistance.


� Thermosets

� Examples:

� Epoxy resins

� Superior performance, relatively costly.

� Epoxy resins have improved (better) strength and stiffness properties over polyesters and have excellent corrosion resistance and resistance to solvents and alkalis. Cure cycles are usually longerthan polyesters, however no by-products (during curing chemical reaction) are produced.

� Flexibility and improved performance is also achieved by the utilization of additives and fillers.

� Phenolics, Flourocarbons, Polyethersulfone, Silicon, Polyurethane, and Polyimides


� Thermosets

� Fibers used:

� Glass, Aramid

(kevlar), Carbon

(graphite), Boron

Matrix (Types – Polymer)� Comparison:

Fair (moderate) solvent resistance

Excellent solvent resistance

Easy fabrication - lower temperature and viscosity

Difficult fabrication – higher temperature and viscosity

Long cure cyclesShort cure (to finish) cycles

Tacky (slightly sticky)Not tacky and easy to handle

Cannot be reprocessedCan be reprocessed (re-melt, re-use)

Definite shelf life (storage)Indefinite shelf life (storage)

Low strains to failure (brittle)High strains to failure (ductile)

Decompose on heatingSoften on heating and pressure, and thus easy to repair

ThermosetThermoplastics

Reinforcement (Function)

� The typical composite consists of a matrix holding reinforcing materials. The reinforcing materials, the most important is the Fibers, supply the basic strength of the composite.

� However, reinforcing materials can contribute much more than strength. They can conduct heat or resist chemical corrosion. They can resist or conduct electricity. They may be chosen for their stiffness (modulus of elasticity) or for many other properties.

Reinforcement (Particles)

Particles (small size)� Important for metals and ceramics matrix composites.

� Particles reinforce a composite equally in all directions(called isotropic).� Impede (stop) dislocation movement in the matrix.� Particle materials: Plastics, Cermets, and Metals.

� Size: microscopic (less than 1 µm) to macroscopic(greater than 1 µm)� For microscopic size (< 1 µm) particles (15% or less the

total composite volume), the imbedded particles strengthens the matrix material.

� For macroscopic size (> 1 µm) particles (25% or more the total composite volume), the imbedded particles share with the carried load of the matrix material.

� Example: composite strengthening in cemented carbides, in which tungsten carbide (80% of the total cement volume) is held in a cobalt binder.

Reinforcement (Particles)� Particles used to strengthen a matrix not the same way as

Fibers. Particles are not directional like Fibers.

� Particles spread at random through out a matrix and

reinforce in all directions equally.

� Cermets(1) Oxide–Based Cermets

(e.g. Combination of Al2O3 with Cr particles)

(2) Carbide–Based Cermets

(e.g. Tungsten carbide, Titanium carbide)

� Metal particles (in Plastic Matrix Composites)

(e.g. Aluminum, Iron & Steel, Copper particles)

� Metal and Dispersion Hardened Alloys particles (in Metal Matrix Composites)

(e.g. Ceramic–oxide particles)

Reinforcement (Particles)• Examples:

- Spheroidite

steel

matrix:

ferrite (α)

(ductile)

particles:

cementite

(Fe 3 C )

(brittle)

60 µm

- WC/Co

cemented

carbide

matrix:

cobalt

(ductile)

particles:

WC

(brittle,

hard)V m :

5-12 vol%! 600µm

- Automobile

tires

matrix:

rubber

(compliant)

particles:

C

(stiffer)

0.75µm

Reinforcement (Particles)

Advantages of Particle reinforcement:

� improved strength

� increased operating temperature

� oxidation resistance

� Examples:

� Aluminum particles in Rubber

� Silicon carbide particles in Aluminum

� Gravel, Sand, and Cement to make Concrete

Reinforcement (Particles & Flakes)

� Nano Particles and Flakes - dispersion strengthened composites (nano composites)

� Small particles or flakes (1 to 100 nm)

� Matrix bears most of the applied load

� Particles hinder or impede motion of dislocations

� Plastic deformation is restricted

� Improves yield and tensile strength.

� Examples:

� Thoria (From Periodic Table of Elements: Th ��

Thorium) dispersed nickel (Ni with up to 3% by volume of ThO2 particles)

� Sintered (bonding by pressure and heat below melting point) aluminum powder (Al matrix with Al2O3 coated Al flakes).

Large-Particle (<1 µm, >1 µm) vs. Dispersion-

Strengthened (1 – 100 nm particles) Composites

Shear ττττ

Strong Particle

>500 nm

Strong Particle

<100 nm Dislocation stopped

Stress field of

dispersion

Dislocation shears through

the dispersionDispersion Strengthened

Large-Particle

Reinforcement (Flakes)

Flakes (big size particles)

� Flat Reinforcement (flat platelet form) in 2-D(reinforce in length & widthdirection due to Flake Shape).

� Two-dimensional particlesranging 0.01 to 1.0 mm.across the flake, with a thickness of 0.001 to 0.005 mm.

� Difficult to orient (align) the flakes.

� Flake materials are Glass, Mica, and Aluminum.

2-D Reinforcement

1-D Reinforcement

Reinforcement (Flakes)

� A flake composite consists of thin, flat flakes held

together by a binder or placed in a matrix.

� Almost all flake composite matrixes are plastic resins.

� Flakes will provide:

� Uniform mechanical properties in the plane of the flakes

� Higher strength

� Higher flexural modulus (bending stiffness)

� Higher dielectric strength and heat resistance

� Better resistance to penetration by liquids and vapor

� Lower cost

Reinforcement (Fibers)

Fibers

� Diameter range from 0.0001 in. to about 0.005 in.(depending on the material).

� Generally circular cross-section, but can also be in the

form of tubular (tubes), rectangle, hexagonal.

� Fibers used can be either continuous (long) or discontinuous (short or Whiskers)

� Continuous fibers (long) – are very long (continuous fiber length). In theory, they offer a continuous path by which a load can be carried by the composite material.

� Discontinuous fibers (Short / Whiskers / Chopped) –are short lengths.

� Length � based on Length to Diameter (L/D) Ratio

� L/D = 100 � (Chopped Fiber / Short Fiber / Whisker)

Reinforcement (Dimension)� Fiber Diameter is very

small (thin or filament).� As fiber diameter becomes

smaller, chances of materialflaw (molecular or crystal dislocations) is reduced. The molecules or crystals are well aligned one after the otherresulting to increase in strength.

� A fiber bundle (strands of fiber filaments) has more surface area in contact to the matrix (increase in load transfer from matrix to fiber) than one solid fiber of the same diameter as the fiber bundle.

� Flexibility – ability to bend increases with a decrease in fiber diameter. Bending stiffness (the resistance to bending moments) increases.

Fiber Strength as a function of Fiber Diameter (Carbon Fiber)

Reinforcement (Types of Fibers)Characteristics / Properties of common fibers:

� Glass

� Many types (from ordinary bottle glass to high purity quartz glass), all can be made into fibers, each type has its own set of properties.

� High strength, low stiffness (elastic modulus), high density, lowest cost (cheapest), chemical resistance, moisture resistance, thermal resistance (low thermal conductivity), electrical resistance (insulator)

� Most widely used fiber (ex. Glass Fiber-Reinforced Plastic

[GFRP] or Fiberglass)

� Uses: piping (pipes), tanks, boats, sporting goods

� Advantages:

� Low cost compared to other fibers

� Corrosion resistance

Reinforcement (Types of Fibers)� Glass

� Disadvantages:

� Relatively low strength

� High elongation (stretches)

� Moderate strength to weight ratio (specific strength)

� Common types used:

� A-Glass

� C-Glass

� E-Glass (Calcium-Aluminoborosilicate) – electrical

(insulator), cheaper, (less than E = 500,000 psi)

� S-Glass (Magnesia-Aluminosilicate) – high tensile strength

(650,000 psi) compared to other glass types, 5 times the tensile strength of steel, about one-third the density of

steel.

Reinforcement (Types of Fibers)

� Glass Fiber manufacturing (processing)

Sizzing Solution is a mixture of:

•Binders – allow

filaments to be packed in

strands

•Lubricants – prevent

abrasion of filaments

•Coupling agents –

better adhesion between

the inorganic glass fiber

and the organic matrix

(during composite

manufacturing)

•Anti-static agents

Reinforcement (Types of Fibers)� Glass Fiber manufacturing (processing)


� Aramid (Kevlar [trade name] – polyamide [nylon]

family, plastic fibers) - aromatic (hexagonal / cyclic)

polyamide fibers.

� For high performance composite application – light weight, high strength, resistance to stress.

� Highest strength to weight ratio (specific strength) of all fibers, high cost.

� Uses � High performance replacement for glass fiber.

� Application � Armor, protective clothing, industrial, sporting goods.

� Advantages:

� Higher strength, lighter than glass

� More ductile than carbon


� Aramid (Kevlar – trade name)

� 2 Commercial Types:

� Kevlar 29 – Low density, high strength.

� Application – Cables, Ropes and Missiles.

� Kevlar 49 – density is higher than Kevlar 29.

� Application – Shipping industry, Aerospace, Automobile,

and Industrial application.

Reinforcement (Types of Fibers)� Graphite (Carbon)

� 2nd most widely used fiber

� Application Areas: aerospace, sporting goods

� High strength (high elastic modulus), low cost (cheap), less dense than glass (low density)

� Graphite fibers are manufactured from any one of the 3 material precursor (origin / start / source):

� Rayon

� Polyacrylonitrile (PAN) – commonly use

� Pitch (petroleum pitch)

� Carbon fibers (produced at 1,316°C) have 93 to 95% carbon content.

� Graphite fibers (produced at more than 1,900°C) has more than 99% carbon content (5 times stronger than steel, density is one-fourth of steel).


� Advantages: Graphite (Carbon)

� high stiffness and strength

� Low density

� Intermediate (moderate) cost

� Properties:

� Standard modulus: 207-240 GPa

� Intermediate modulus: 240-340 GPa

� High modulus: 340-960 GPa

� Diameter: 5-8 µm, smaller than human hair

� Fibers grouped into tows or yarns (bundle) of 2,000-12,000 fibers per bundle (strand)


Carbon Fiber manufacturing (processing)

� Carbon fiber is produced using PAN (Polyacrylonitrile)

with the help of these processing stages:

� Stabilization – by holding in tension PAN fibers are stretched to align and are oxidize (200OC – 300OC) in air.

� Carbonization - PAN fiber are heated (1,000OC – 1,500OC to eliminate [vaporize] oxygen, nitrogen and hydrogen)until transformed into carbon fibers.

� Graphitization - heating at more than 1,900OC to produce a product of high elasticity.

Reinforcement (Types of Fibers)� Carbon Fiber manufacturing (processing)

� Fiber precursor (Polyacrylonitrile) heated and stretched to align structure and remove non-carbon material.

Reinforcement (Types of Fibers)� Boron

� High strength and stiffness (high elastic modulus), highest density, highest cost (limit its application in Aerospace), has tungsten filament at its center.

� Good Compressive strength, Large Fiber Diameter (200 µm).

� Metal (Steel filaments)

� Reinforcing fiber in plastics

� Polyethylene (PE) – trade name “Spectra Fiber”

� Commonly use in Textile Industry (textile composites production)

� High strength

� Extremely Light weight

� Low range of temperature usage (application)

Reinforcement (Types of Fibers)� Ceramic Fibers

� Main fiber materials: Silicon carbide (SiC) and Aluminum oxide (Al2O3).

� High Elastic modulus, used to strengthen low-density, low-modulus metals (Aluminum, Magnesium).

� Very high temperature applications (e.g. engine components)

� Silicon carbide fiber - in whisker (short fiber) form.

� Excellent temperature resistance (matrix material use is also Ceramic)

� Not commonly use

� Advanced Fibers (high strength and stiffness [elastic modulus], low weight)

� Nylon, Silicon carbide, Silicon nitride, Aluminum oxide, Boron carbide, Boron nitride, Tantalum carbide, Steel, Tungsten, Molybdenum.


Fiber Glass

Graphite Fiber

Kevlar Fiber

Kevlar/Carbon Hybrid

Fibers in Textile Form

Fiber Mechanical Properties

Steel: Density = 7.87 g/cc; Tensile Strength (Stress) = 0.380

GPa; Elastic Modulus = 207 GPa

Aluminum: Density = 2.71 g/cc; Tensile Strength (Stress) = 0.035

GPa; Elastic Modulus = 69 GPa

Fiber Mechanical Properties

Fiber

Type

Density

(kg/m3)

E-

Modulus

(GPa)

Tensile

Strength

(GPa)

Elong.

(%)

E-Glass 2.54 72.5 1.72-3.45 2.5

S-Glass 2.49 87 2.53-4.48 2.9

Kevlar 29 1.45 85 2.27-3.80 2.8

Kevlar 49 1.45 117 2.27-3.80 1.8

Carbon

(HS)

1.80 227 2.80-5.10 1.1

Carbon

(HM)

1.80-1.86 370 1.80 0.5

Carbon

(UHM)

1.86-2.10 350-520 1.00-1.75 0.2

Fiber Strength

Fiber Density (g/cm3)

1.38

1.59

1.99

1.99

2.76

8

0 2 4 6 8 10

Aramid

Carbon

S-Glass

E-Glass

Alum

Steel

Fiber Tensile Strength (σ)

x103 psi

500

525

530

625

20

60

0 200 400 600 800

E-Glass

Aramid

Carbon

S-Glass

Steel

Alum

Fiber Strain (εεεε) To Failure

(%)

1.4

2.8

4.8

5

0.2

0.16

0 1 2 3 4 5 6

Carbon

Aramid

E-Glass

S-Glass

Steel

Alum

Fiber Tensile Modulus (E)

x 106 psi

10.5

12.6

19

33.5

29

10

0 10 20 30 40

E-Glass

S-Glass

Aramid

Carbon

Steel

Alum

Fiber CTE – Longitudinal

-2 0.5

2.9

5

6.5

12.6

-2

0

2

4

6

8

10

12

14

Aramid

Carbon S-Glass E-Glass Steel Alum

x10-6 mm/0C

CTE = coefficient of thermal expansion

Reinforcement (Organization/Design)

In fiber composites, fibers reinforce along the line of their length. Reinforcement may be mainly 1-D, 2-D or 3-D. Figures shows the 3 basic types of fiber orientation.

� 1-D (One-Dimensional) gives maximumstrength and stiffness are in one direction –fiber direction.

� 2-D (Planar or 2-Dimensional) gives strengthin two directions (ex. in the form of 2 dimensional woven fabric).

� 3-D (Random or 3-Dimensonal) gives strength equally in all directions (3 directions) – ISOTROPIC. Fibers are in different directions. The composite material has the same properties in all directions (length, width, and height directions).

Fiber Alignment

(Short Fiber or Whiskers)

aligned

continuousaligned random

discontinuous


� Reinforcement Organization (Design) – fiber

arrangement affects the properties of a composite

material.

Design Types for Continuous (long) Fiber:

� Unidirectional – non- woven, oriented (straight) in a single direction.

� Textile Form (Fabric)

� Woven – series of interlaced yarns at 90O to each other

� Braided – series of intertwined spiral yarns

� Knitted – series of inter-looped yarns

� Tri-axial Yarns Yarn = strand (bundle) of fibers


� Unidirectional Fiber – Design Variations


� Textile Form (Fabric)

Fiber Glass

Graphite Fiber

Kevlar Fiber

Kevlar/Carbon Hybrid

Fibers in Textile Form


Woven Fabric

� 2 systems of yarns(strand / bundle) interlaced in series to each other at right angles (90O) to create a single layer with isotropic or biaxial properties.

� Physical Properties:

� Construction – ends & picks (pull through)

� Weight

� Thickness

� Weave Type

Warp – fasten or hold

Basic Weave Types

Plain Weave

Basic Weave Types

Satin 5HS

Basic Weave Types

2 x 2 Twill

Basic Weave TypesNon-Crimp

Crimp – wave (bending)


Braid (Braiding or Braided)� 2 sets of yarns, which are

helically (spiral) intertwinedin series.

� Oriented to the longitudinal axis of the braid.

� High level of conformability(easily follow shape), relative low cost, and easy to manufacture.� Tubular braid form –

braiding is done on a tube shape guide (solid tube metal).� Finished tubular braid is

pull-out from the tube shape guide and can be flattened or cut for use in non-tubular products.

Longitudinal Axis

Types of Braids


Triaxial Yarns

� A system of Longitudinal

Yarns are held in placeby the Braiding Yarns.

� Longitudinal Yarns:

� Add dimensional stability, improve tensileproperties, stiffness, and compressive strength.

� Can be added to the coreof the braid (tubular braid) to form a solid braid.


Knit

� Series of Inter-looped

Yarns

Knit


� Fibers in Textile (Fabric) Form

Fabric (fiber organization) Effect on

Composite Material Properties

Laminate Composites� Stack (2 or more layers

of the same or different materials) of Laminaarranged with their main reinforcement in at least2 or more different directions to give strength where needed.� Lamina (thin layer –

laminae) – any arrangement of fibers (unidirectional or woven)in a matrix. Usually this arrangement is flat, although it may be curved, as in a shell.

� Example: Speedboat hulls are made of Laminate Composites.

Laminate Composites� Sheets of continuous fiber

composites laminated (bonding thin layers together) wherein each layer has the fiber orientedin a given direction.

� Combine constituents(components of different materials) to produce properties that neither constituent alone would have.

� In Laminate Compositesouter metal is not called a matrix but a face. The inner metal, even if stronger, is not called a reinforcement

but a base.

Laminate Composites� Belong to Structural (put

together) Composites

� Stacked and bonded fiber-reinforced sheets

� stacking sequence: e.g., 0º/90º or 0°/45°/90º.

� benefit: balanced, in-plane stiffness (elastic modulus).

� Reinforced–Layer composites

� Fiber Direction (angle)

� 0O – flexural strengthening

� 90O – column wraps

� +/- 45O – shear strengthening

� Angle varies by application

Combined Composites� Combine several different

materials into a single

composite (Hybrid Laminate).

� Reinforced-Laminates

(MMC, CMC, PMC) well

bonded with steel,

aluminum, copper, rubber, gold, etc.

� Example: Modern Ski –

combination of wood

(natural fiber composite), and layers of other

materials as laminate

composites.

Particle, Fiber, and Structural (Sandwich)composite.

Combined

Composites

honeycomb

adhesive layer

face sheet

Sandwich Panel Composites� Sandwich Structures� Belong to Structural (put together) Composites

� Consists of a Skeletal 3-D Core (commonly use –Honeycomb) that holds a second material (in Foam form).

� Thin composite skins (face sheet) bonded to thickerlightweight core.

� Lightweight (low density Honeycomb core)

� High bending stiffness (high flexural modulus � E)

Sandwich Panel Composites (concept)� Sandwich Panels Composites are a very efficient way of

providing high bending stiffness (Flexural Modulus � E)at low weight.

� Composite Skins (face sheet - stiff and strong) carry the bending loads.

� Core resists shear loads.

� The principle is the same as a traditional “I” beam.

Sandwich Panel Composites (concept)

� Thick, Lightweight Core – gives large increase in

second moment of area (without weight increase in the

Sandwich Panel Composite structure).

� Core needs good shear stiffness (Shear Modulus � G)

and strength (Shear Loads).

� Thin Composite Skins (bonded to thick, lightweight Core)

carry tension and compression loads (bending loads).

The stiff, strong facing

skins carry the bending

loads, while the core

resists shear loads.

Total deflection =

bending + shear

Bending depends on the skin

properties

Shear depends on

the core properties

Sandwich Panel Composites (concept)

� Bending stiffness (flexural modulus � E) – increased

by making beams or panel thicker � sandwich of lightweight core (very small increase in weight).

Sandwich Panel Composites (core)� Core Materials and Comparison

�Excellent crush

strength and stiffness

�Constant crush

strength

�Structural integrity (do

not break apart)

�High strength

�High fatigue resistance

�Over-expanded

Honeycomb cells

design for curvature

application

�Low crush strength

and stiffness

�Increasing stress

with strain

�Friable (brittle)

�Limited strength

�Fatigue

�Cannot be formed

around curvatures

Polymer (in Foam form):

�Polyvinyl chloride (PVC)

�Polymethacrylimide (PMA)

�Polyurethane (PU)

�Polystryrene (PS)

�Phenolic

�Polyethersulfone (PES)

Honeycomb Core

Advantages

PropertyCore Materials

Sandwich Panel Composites (core)

� Core Materials and Comparison

�Excellent strength to

weight ratio

�Excellent moisture

resistance

�Self-extinguishing (fire),

low smoke

�High density

�Absorbs moisture

�Degradation (loss of

quality or performance)

�Flammable (easily

burns in fire)

Wood-based:

�Plywood

�Balsa (lightweight soft

wood)

�Particle board

Honeycomb Core

Advantages

PropertyCore Materials


Some Core Materials Properties:

� Polymer in Foam form

� Polyvinyl chloride (PVC)

� Linear – high ductility, low properties

� Cross-Linked – high strength and stiffness, but brittle

� 50% reduction of properties at 40OC - 60OC

� Chemical breakdown (HCl vapor) at 200oC

� Polyuretthane (PU)

� Inferior (lower) properties compared to PVC at ambient(environment or sorroundings) temperatures.

� Better property retention (max. 100oC)

� Phenolic

� Poor mechanical properties

� Good fire resistance

� Strength retention up to 150oC


Some Core Materials Properties:

� Wood-based

� Balsa

� Efficient and low cost

� Absorbs water (swelling and decompose)

� Not advisable for primary hull and deck structures (water or

sea exposure – absorbs moisture)

� Advisable for internal bulkheads (partitions)


� Honeycomb structure – hexagonal cells


� Over-expanded Honeycomb

Cells – give extra formability

(can follow shapes).

� Regular (symmetrical)

Honeycomb Cells


� Honeycomb is available in polymer (thermoplastic or thermoset), carbon, aramid (kevlar), and GRP(glass-fiber reinforced polymer).

� 2 common types of Honeycomb use in aerospace applications:

� Aluminium Honeycomb

� Aramid Fiber Honeycomb (Nomex) – honeycomb made of aramid fiber-paper impregnated with phenolicresin.

Aluminum Honeycomb• relatively low cost

• best for energy absorption

• high strength to weight ratio

• thinnest cell walls

• smooth cell walls• conductive heat transfer

• electrical shielding

• machinability Aramid Fiber (Nomex) Honeycomb

• flammability / fire retardance (slow

down fire)

• large selection of cell sizes,

densities, and strengths• formability (can follow shape)

• insulative (insulator)

• low dielectric (electrical insulator)

properties

Sandwich Panel Composites (core)� Sandwich constructions made with

other core materials (Balsa, Foam, etc.) have large surface available for bonding the skins (high probability of non-uniform

adhesive distribution).

� Honeycomb core needs only a small fillet of adhesive placed at the edge of the cell walls.

� Performance of Sandwich Panel Composite depends on:

� Uniformity of adhesive

distribution.

� Manufacturing (processing)

factors (resin viscosity,

temperature, vacuum [porosity],

etc).

Composite Material Strength

� Depends on following Factors:

� Fiber factors:

� Fiber type (kind)

� Fiber strength

� Fiber length

� Fiber size (diameter / bundle / strand)

� Fiber volume (fiber volume to composite volume – fiber volume

fraction)

� Fiber defects (crystal or molecular / atomic alignment / arrangement).

� Fiber orientation (angle orientation)

� Fiber shape (organization / design / architecture).

� Matrix factors:

� Matrix type (kind).

� Matrix properties (physical, mechanical, chemical).

Composite Material Strength� Depends on following Factors:

� Fiber-Matrix factors:

� Homogeneity (uniformity) of mixture(reinforcement and matrix).

� Natural roughness (mechanical interlocking between fiber and matrix).

� Coefficient of thermal expansion(CTE) of matrix (same with fiber).

� Bonding quality (interfacial(common boundary) bonding –coupling agents) of the fiber and matrix (equal stress distribution).

� Voids (empty spaces).

� Moisture absorption (coupling agents – prevent moisture entry). Moisture can damage (chemical reaction) the reinforcement, matrix, and interphase bonding.


� Depends on following Factors:

� Bonding Quality – interfacial bonding (coupling agents) between

fiber and matrix.

� The chemistry behind the interfacial bonding of fiber and matrix is

very important.Fibers are debonded

(pulled-out) from matrix

if interfacial bonding is

insufficeint.


� Break Surface

� Fiber-Matrix Adhesion

Loose fibers

are pulled-out

(insufficient

adhesion).

Good Fiber-Matrix Adhesion

Poor Fiber-Matrix Adhesion


� Function of the Coupling Agent

� Interfacial bonding (chemical bonding at small extent) between the fiber and matrix.

Effect of Fiber Type

Property E-Glass/

Epoxy

S-Glass/

Epoxy

Aramid/

Epoxy

Carbon/

Epoxy

Fiber Volume

(% in decimal form)

0.55 0.50 0.60 0.63

Longitudinal Modulus (GPa) 39 43 87 142

Transverse .Modulus (GPa) 8.6 8.9 5.5 10.3

Shear Modulus (GPa) 3.8 4.5 2.2 7.2

Poisson’s Ratio (unitless) 0.28 0.27 0.34 0.27

Long.Tensile Strength (MPa) 1080 1280 1280 2280

Compressive Strength (MPa) 620 690 335 1440

Properties Of Unidirectional Composites

Properties of Reinforced Plastics (PMC)Mechanical properties of reinforced plastics (PMC) vary with the kind (fiber type), shape (organization / architecture), orientation(angle orientation), length, and relative volume (fiber volume to composite volume – fiber volume fraction), and orientation of the reinforcing material (fibers).

Effect of type, length, % volume (fiber volume to composite volume – fiber

volume fraction), and orientation of fibers in a fiber reinforced plastic (nylon).

Recycling of Composite Materials� Complex process because:

� Different types of composites.

� Different kinds of materials that made up a composite.

� Recycling process:

� Mechanical Process – cheap process.

� Shredding (strips) � separation � washing � grinding �

drying � extrusion (semi-soft material passes through mold nozzle – die).

� Recycled composite material � powder or fiber form.

� Powder form � reused as paste (matrix) for sheet-molding compound (SMC – follow complex shape).

� Fiber form � reused for reinforcement in bulk-molding compounds (BMC – thick, can follow simple shapes).

� Recycled composite � do not use more than 20% volume fraction (recycled composite volume to composite volume) as replacement – degrade (already used materials) impact resistance and electrical properties of product.

� Recycled plastics are limited only to fences and benches.

Recycling of Composite Materials� Recycling process:

� Chemical Process

� Pyrolysis – material decomposition (break down into simpler components) by heating in an oxygen-freeenvironment (sealed).

� Expensive process.

� Gases and Oils (absorbed due composite usage) are recovered.

� Recycle composite automobile parts.

� Residues � fillers in concrete and roof shingles (small flat tile).

� Carbon composite waste � has chlorine content – needs dehalogenation (removal of halogens - Chlorine, Fluorine, Iodine, Bromine, or Astatine).

� Use of Recycled Glass Fibers (from recycled composites) – PROBLEM � low compressive strength of the new material (effects of recycling process on glass fibers).

Recycling of Composite Materials

� Recycling process:

� Chemical Process

� Incineration – burning (in order to destroy).

� If composites contiutents that cannot be separated (due

to absorbed toxic materials from toxic environment during

service life).

� Use as Fuel (polymer matrix composites heating value =

11,622 kJ/kg � half of coal).

� For Low scarp (waste) volume, Minimal cost (just burning),

High-volume reduction (ashes), No residual (recyclable)

material.

Mechanics Terminology� Mechanical Analysis of Composites

� Different from conventional materials – metals (composites consist of 2 or more materials).

� Analysis approach (composite):

� Micro-mechanics of Lamina – find average properties

(stiffness, strength, thermal and moisture expansion

coefficient) of a composite ply (lamina) � optimize stiffness

(elastic modulus � E) and strength (stress capacity � σ).

� Macro-mechanics of Lamina

� Develop stress-strain relationship (loading at off-axis or along

symmetry-axis of lamina).

� Develop relationship for stiffness, thermal and moisture

expansion coefficients, and strengths of angle plies (fibers

oriented at certain angle).

� Failure theories of lamina � based on applied stresses and

strength properties.

Mechanics Terminology

� Mechanical Analysis of Composites

� Analysis approach (composite):

� Macro-mechanics of Laminate – laminate (stacked laminas)

analysis.

� Stiffness, strength, thermal and moisture expansion

coefficients, of the entire laminate.

� Failure of laminate � based on applied stresses and failure

theories � each ply (lamina).

� Structural analysis – mechanical design (base on micro- and

macro-mechanical analysis of lamina and laminate) of

structures made of composite materials.

Mechanical Analysis of Composites

Mechanics Terminology� Some Important Terms:

� Isotropic Material – properties are the same in all directions (ex.

Elastic / Young’s Modulus of steel is same in all direction).

� Homogeneous Material – made of one type of material. Uniform

properties (isotropic) in any location.

� Anisotropic Material – properties are different in all directions.

� Non-homogeneous Material – made of more than one type of

material. Properties depends on location.

� Composite Material – compose of matrix and reinforcement

(fiber). Properties depend on location – matrix (weak), fiber

(strong along fiber but weak transverse to fiber). Non-

homogeneous and anisotropic.

� Lamina – a single flat layer (ply) of unidirectional or woven fibers

in a matrix.

� Laminate – stack of plies (layers of laminas). Individual layer can

have different materials and various fiber orientation.

Mechanics Terminology� Some Important Terms:

� Hybrid Laminate (Combined Composite) – more than one fiber type (matrix system) in a laminate.

� Interply Hybrid Laminates – each ply (lamina) is made of different composite system (composite type) . Example: Car Bumper � glass fiber – epoxy layer (torsional rigidity) and graphite fiber – epoxy layer (stiffness).

� Intraply Hybrid Composites – each ply (lamina) has two or more fiber types. Example: Golf Clubs (stick for hitting golf balls) � graphite (torsional rigidity) and aramid (tensile strength & toughness) fibers.

� Interply-Intraply Hybrid Laminates – some plies (laminas)having two or more fiber types while other plies (laminas)have distinct composite system (composite type).

� Resin Hybrid Laminates – some plies (laminas) has flexible resin (matrix) while other plies (laminas) has rigid resin(matrix) � increase in shear and fracture properties by 50%(compared to all-flexible or all-rigid resin laminate).

Micro-mechanical Analysis

of a Lamina



Cum Fructo



Cum Laude


Mechanics – study of forces acting on a rigid body.

a.) Statics – branch of mechanics which considers the action of

forces in producing rest (equilibrium) of a body.

b.) Dynamics – branch of mechanics which treats of the motion of

bodies (kinematics) and the action of forces in producing a

change in their motion (kinetics).

Force (F) – a push or pull.

Pressure (P) – uniformly applied force over an area, measured as

force per unit of area (Pa or N/m2).

Basic Mechanics

Stress – an applied force or system of forces that

tends to strain (deform) a body.

Basic Strength of Materials

Strain – deformation (dimensionless) produced by

stress. Ratio of difference in length to the actual

length.

LStrain

δε = ,

⊥

=A

FStress σ ,

(m) ],difference[length n Deformatio

(m) Length, Initial L

(unitless) strain,

:where

=

=

=

δ

ε

( )

( )2

m

N

m force, to area A

(N) force, F

or Pa stress,

:where

2

⊥=

=

=σ

Stress - Strain Curves

Engineering Stress-Strain Curve for Steel

Stress-Strain Curve

for different metals

Stress - Strain Curves� Stress-Strain Diagram

� Elastic Modulus (E) – slope of stress-strain curve at Elastic region.

� Yield Strength (σy) at pt. B – stress that will produce small

amount of permanent deformation (ε = 0.002).

• Stress where noticeable plastic deformation occurs.

when εp = 0.002

Yield Strength, σy

For metals agreed upon 0.2%tensile stress, σ

engineering strain, ε

σy

εp = 0.002

Elastic

recovery

ndeformatio plasticεp =


� Plastic Deformation – begins when elastic limit is exceeded (more than).

� Strain Hardening – as plastic deformation increases the material becomes stronger (load to extend or strain increases until maximum value).


� Ultimate Tensile Strength (σult.) – ratio of maximum load to

original cross-sectional area of the material.

� Necking – cross-sectional area decreases rapidly and the load required to continue deformation drops off until the specimen Factures.

NOTE:

Broken Lines

(CE’) consider

the thinning

(necking) of

the cross-

section of the

material.

• Maximum possible engineering stress in tension.

• Metals: occurs when necking starts.

• Ceramics: occurs when crack propagation starts.

• Polymers: occurs when polymer backbones (long chain molecules) are aligned and about to break.

Ultimate Tensile Strength, σult.

Ductile vs. Brittle Behavior

� Material behavior under load:� Ductile – high strain

(more deformation / elongation).

� Brittle – low strain (little deformation / elongation)� Fracture Stress is also

the Ultimate Stress.

� Completely Brittle Material (ex. Concrete, Stone, Glass, Ceramic materials) – fracture immediately at elastic limit

� Brittle Metal (ex. Cast iron) – small plastic deformation (ductility) before facture.

NOTE:

A = Elastic Limit

B = Fracture

AB = Plastic Deformation

Stress - Strain Curves

Stress-Strain Curve for Composites

Young’s Modulus – measure of the elastic force of any

substance, expressed by the ratio of a stress on a given unit of

the substance to the accompanying distortion (strain). Simply –

ratio of stress to strain.

ε

σE =


σ

Linear- elastic

1

E

ε

( )( )(unitless) strain, ε

stress, σ

or Pa modulus, )(Stiffness Flexural / sYoung' / Elastic E

:where

2

2

m

N

m

N

=

=

=

Hooke’s Law – stress is proportional to strain (deformation).

Applicable within elastic limit of material.

Poisson’s Ratio (υυυυ) – ratio of transverse contraction strain (εtransverse

or ε2) to longitudinal extension strain (εlongitudinal or ε1) � along

stretching force direction. Poisson’s Ratio is unitless.


εEσ =

1

2

allongitudin

transverse

ε

ε -

ε

ε -

12υ ==

( )( )(unitless) strain, ε

stress, σ

or Pa modulus, )(Stiffness Flexural / sYoung' / Elastic E

:where

2

2

m

N

m

N

=

=

=

NOTE:

(-) = contraction (+) = extension


� Shear Strain (γγγγ) –angular change in a right angle.

θtanθγha ===

NOTE:

At small angle value (θ)

tanθ = θ

Where:

γγγγ = shear strain, (unitless)

If use: tanθ = θ is in degrees

If use: θ = θ is in radian (rad.)

Conversion: 180O = π radian


Material Behavior in Principal

Material Axes:

� Isotropic materials

� Uni-axial loading

1122

111

ευε

εEσ

−=

=

( )12

112

υ12

EG

+=

E = Elastic / Young’s

Modulus / Flexural

(Stiffness), (Pa or N/m2)

G = Shear (Rigidity)

modulus, (Pa or N/m2)

σσσσ = stress, (Pa or N/m2)

εεεε = strain, (unitless)

ττττ = shear stress, (Pa or N/m2)


υυυυ = poisson’s ratio, (unitless)

1 = longitudinal

2 = transverse

( )tanθγ

τ

12

121212

IIAF

12

12G

γGτ

==

=

Beam Theory

Beam - long piece of material (timber or metal) commonly used as

horizontal support in construction.

F = applied load

I = moment of inertia

L = beam length

E = Elastic / Young’s / Flexural Modulus (Stiffness)

Simply supported beam loaded at center

yI

Mσ ,Stress

48EI

FLδ ,Deflection Maximum

3

=

=

Beam Theory

yI

M σ=

Basic equation in bending stresses in beams

4)(

FLmomentM = 12

3bh

I =2

hy =

We know,

We can find the stress using the above

equations.

Cross sectional view of beam

Density & Mass Fractions (Rules Of Mixture)

� Density

c

cm

cρ ν=

� Mass of Composite

Laminate:

mfc mmm +=

Where:

c = composite

m = matrix

f = fiber

ρρρρ = density, (kg/m3)

m = mass, (kg)

νννν = volume, (m3)

M = mass fraction, (decimal form)

� Mass Fraction of Composite Laminate:

c

f

m

m

fM =c

m

m

m

mM =

mf MM1 +=f

fm

fρ ν=m

mm

mρ ν=

Volume Fractions (Rules Of Mixture)

ffmmc ρVρVρ +=

Where:

c = composite

m = matrix

f = fiber

νννν = volume, (m3)


V = volume fraction, (decimal form)

� Volume Fraction of Laminate Composite:

� Density of Laminate Composite:

mf VV1 +=

c

f

fV ν

ν=

c

m

mV ν

ν=

mfc ννν +=

mmffc VρVρρ +=

� Volume of Laminate

Composite:

Mass Fraction & Volume Fractions

� Mass Fraction of Composite Laminate:

( )( )( )

( )fVVf VMmfmρ

fρ

mρfρ

=

+ ( )( )( )mVV-1

1m VM

mmmρfρ

=

+

Where:

c = composite

m = matrix

f = fiber



M = mass fraction, (decimal form)m

m

f

f

c ρ

M

ρ

M

ρ1 +=

� Density of Composite Laminate:

Strength (Rules Of Mixture)

( )

m

f

f

f

m

m

f

f

2 E

V-1

E

V

E

V

E

V

E1 +=+=

( ) mfffmmff1 EV-1EVEVEVE +=+=

� If consider fiber to be isotropic (reinforce in all directions),

the Rule of Mixtures for Composite E and G is:

( )

m

f

f

f

m

m

f

f

12 G

V-1

G

V

G

V

G

V

G1 +=+=

Where:

f = fiber

m = matrix

1 = longitudinal

2 = transverse

Where:


E = Elastic / Young’s / Flexural Modulus (Stiffness),

(Pa or N/m2)

G = Shear (Rigidity) Modulus, (Pa or N/m2)

• Elastic Modulus of Composites (Ec) :-- two approaches.

Data:

Cu matrix

w/tungsten

particles

0 20 40 60 80 100

150

200

250

300

350

vol% tungsten

E(GPa)

lower limit:

1

Ec

=Vm

Em

+Vp

Ep

c m m

upper limit:

E = V E + VpEp

(Cu) (W)

“rule of mixtures”

Strength (Rules Of Mixture)

• Application to other properties:-- Electrical conductivity, Ke � Replace E in the above equations

with Ke.

-- Thermal conductivity, K � Replace E in above equations with K.

Density, Volume and Mass Fractions

� Fiber Properties


� Matrix Properties


� Example:

� 1.) A glass/epoxy lamina consists of a 70% fiber volume fraction. Determine the following:

� lamina (composite) density

� mass fractions of glass and epoxy

� composite volume if lamina is 4 kg.

� volume and mass of glass and epoxy

� Elastic (E1 & E2) and Shear (G) modulus of lamina if

glass reinforces in all directions

� Solution: use Table 2.1 and 2.2

� Glass fiber specific gravity, S.G.f = 2.5 (unitless)

� Recall:

C)0 C,100 (liquid, 1,000ρ S.G. 00

m

kg

wρ

ρ

f 3w

f ≥≤==

( ) ( )( ) 3m

kg

wff 2,5001,0002.5ρS.G.ρ ===

ρρρρf = fiber density

ρρρρw = water density

1 = longitudinal

2 = transverse


� Example:

� Solution: use Table 2.1 and 2.2

� Epoxy matrix specific gravity, S.G.m = 1.2 (unitless)

� Composite density �

� Mass fraction of glass fiber (Mf)

( ) ( )( ) 3m

kg

wmm 1,2001,0001.2ρS.G.ρ ===

ρρρρm = fiber density Vf = volume fraction fiber

Vm = volume fraction matrix

( )fmffmmffc V-1ρVρVρVρρ +=+=

( )( ) ( )( ) Answer 2,1100.7-11,2000.72,500ρ 3m

kg

c =+=

( )( )( )

( )( )

( )( ) ( )( )fV-1VfVVf VVM

ffmρfρ

mρfρ

mfmρfρ

mρfρ

=

=

++

( )( )( ) ( )

( ) Answer 83.00.7M0.7-10.7f

1,200

2,500

1,200

2,500

=

=

+

Recall: 1 = Vf + Vm

Density, Volume and Mass Fractions� Example:

� Solution:

� Mass fraction of epoxy matrix �

� Composite volume (lamina)

� Glass fiber volume �

� Epoxy matrix volume

Answer 0.170.83-1Mm ==fmmf M-1MMM1 =→+=

( )( )cffv

v

f vVvVc

f =→=

Answer m 0.0019vρ 3

2,1104

ρ

m

cv

m

cc

c

c

c ===→=

ρρρρc = composite density mc = composite mass

( )( ) Answer m 0.00130.00190.7v 3

f ==

fcmmfc vvvvvv −=→+=

Answer m 0.0006.00130-0.0019v 3

m ==

vc = composite volume vf = fiber volume vm = matrix volume

Mm = mass fraction matrix

Density, Volume and Mass Fractions� Example:

� Solution:

� Glass fiber mass (mf) �

� Epoxy matrix mass (mm) �

� Elastic modulus (E1)

� From Table 2.1 and 2.2 � E1f = 85 GPa (glass) E1m = 3.4 GPa

(epoxy)

( )( ) Answer kg 3.250.00132,500vρm fff ===

fffv

m

f vρmρf

f =→=

mmmv

m

m vρmρm

m =→=

( )( ) Answer kg 0.720.00061,200vρm mmm ===

( ) mfffmmff1 EV-1EVEVEVE +=+=

( )( ) ( )( ) Answer GPa 60.523.40.7-1850.7E1 =+=


� Example:

� Solution:

� Elastic modulus (E2)

� From Table 2.1 and 2.2 � E2f = 85 GPa (glass) E2m = 3.4

GPa (epoxy)

( )3.4

0.7-1

850.7

12E

+=

( )

m

f

f

f

m

m

f

f

2 E

V-1

E

V

E

V

E

V

E1 +=+=

Answer GPa 10.36E2 =


� Example:

� Solution:

� Shear modulus (G)

� From Table 2.1 and 2.2 � Gf = 35.42 GPa (glass) Gm = 1.308 GPa

(epoxy)

Answer GPa 4.01G =

( )m

f

f

f

m

m

f

f

12 G

V-1

G

V

G

V

G

V

G1 +=+=

( )1.308

0.7-1

35.420.7

112GG

+==

Void Content� Void (empty spaces) – affects the mechanical properties of a

composite material.

� Theoretical (computed) composite density higher than

experimental (actual) density.

� 1% increase void content = 2% to 10% decrease in mechanical

properties of composite material.

� Composite volume (vc) – consider presence of void (empty space).

� Void volume fraction (Vv)vmfc vvvv ++=

vmf

v

c

v

vvv

v

v

v

vV++

==

vc = composite volume, (m3)

vf = fiber volume, (m3)

vm = matrix volume , (m3)

vv = void volume, (m3)

Vv = void volume fraction, (unitless)

ρρρρce = experimental composite density, (kg/m3)

ρρρρct = theoretical composite density, (kg/m3)ct

cect

ρ

ρρ

vV−

=

Void Content

� Experimental (actual) composite density (ρρρρce)

� Theoretical (computed) composite density (ρρρρct)

c

c

v

m

ceρ =

mf

mf

mf

c

vv

mm

vv

m

ctρ +

+

+==

mc = composite mass (by weighing), (kg)

vc = composite volume (by submersion into a liquid), (m3)

mf = fiber mass, (kg)

mm = matrix mass, (kg)

vf = fiber volume, (m3)

vm = matrix volume, (m3)

Void Content� Example:

� 2.) Base on Problem 1, the glass/epoxy (70% fiber volume fraction) composite has a volume of 0.0020 m3 in actual test(submersion). Determine the following:

� void volume (vv)

� experimental composite density (ρρρρce)

� void volume fraction (Vv)

� Solution:

� Void volume (vv)

� Experimental composite density (ρρρρce)

( )mfcvvmfc vvvvvvvv +−=→++=

( ) Answer m 0001.0006.00013.00020.0v3

v =+−=

[ ]( )c

v

ct

cect

c

v

v

v

tcceρ

ρρ

v

v

v 1ρρV −=→==−

As solved in Problem 1:

vf = 0.0013 m3

vm = 0.0006 m3

Void Content

� Example:

� Solution:

� Experimental composite density (ρρρρce)

� As solved in Problem 1 � ρρρρc = ρρρρct = 2,110 kg/m3

� Void volume fraction (Vv)

Answer 05.0V0.00200.0001

v

v

vc

v ===

[ ]( ) Answer 2,004.512,110ρ 3m

kg

0.00200.0001

ce =−=

mf

mf

c

c

vv

mm

v

m

tcρ +

+==

Elastic Modulus� Fiber, Matrix, and Composite

are assumed to be of the samewidth (h) but of thicknesses tf

(fiber), tm (matrix), and tc

(composite).

� Fiber Area (Af)

� Matrix Area (Am)

� Composite Area (Ac)

( )( )htA ff =

( )( )htA mm =

( )( )htA cc =

Elastic Modulus

� Fiber volume fraction (Vf)

( )( )ccc AF σ=

� Matrix volume fraction (Vm)

� And � 1 = Vf + Vm

mfc FFF +=

( )( )( )( )( )( ) c

f

cc

cf

c

f

t

t

Lht

Lht

v

v

fV === ( )( )( )( )( )( ) c

m

cc

cm

c

m

t

t

Lht

Lht

v

v

mV ===

� Load taken by Composite, Fiber and Matrix.

� Load taken by Composite �

� Load taken by Fiber �

� Load taken by Matrix �

( )( )fff AF σ=

( )( )mmm AF σ=

v = volume

f = fiber

m = matrix

V = volume fraction

Lc = composite length, (m)

F = force, (N)

Elastic Modulus

� Stresses (σσσσ) taken by:

� Composite (σσσσc) ��

� Fiber (σσσσf) �

� Matrix (σσσσm) �

� Elastic Modulus (E) �

� Load Ratio of Fiber (Ff) to the Composite (Fc)

( )( )mmm εEσ =

( )( )fE

E

F

FV

1

f

c

f =

mmff1 VEVEE +=

( )( )ccc εEσ =

( )( )fff εEσ =

E1 or Ec = composite elastic

modulus

V = volume fraction

f = fiber

m = matrix


E = elastic modulus,

(Pa or N/m2)

Elastic Modulus


Elastic Modulus

� Example:

� 3.) Base on Problem 1, for the glass/epoxy (70% fiber volume fraction) composite, find the ratio of load taken by the fibers to that of the composite.

� Solution:

� Load Ratio of Fiber (Ff) to the Composite (Fc)

� From Table 2.1 � Ef = 85 GPa (glass)

� E1 = 60.52 GPa (composite longitudinal elastic modulus �solved

in Problem 1)

( )( )fE

E

F

FV

1

f

c

f =

( )( ) Answer 98.00.760.52

85F

F

c

f ==

Ultimate Strength of a Uni-directional

Lamina

� Ultimate failure strain

of Fiber (εεεεf)ult

� Ultimate failure strain

of Matrix (εεεεm)ult

� Composite tensile

strength (σσσσ1)ult

( ) ( )( ) ( )( )( )ultfmfultffult1 εEV-1σVσ +=

( ) ( )

f

ultf

E

σ

ultfε =

( ) ( )

m

ultm

E

σ

ultmε = ult = ultimate V = volume fraction

m = matrix E = elastic modulus

f = fiber σσσσ = stress


Lamina� Fiber Properties


Lamina� Matrix Properties


Lamina� Example:

� 4.) Base on Problem 1, for the glass/epoxy (70% fiber volume fraction) composite, find the matrix ultimate failure strain (εεεεm)ult , the composite ultimate tensile strength (σσσσ1)ult , and the fiber ultimate failure strain (εεεεf)ult .

� Solution:

� From Table 2.1 � Ef = 85 GPa (glass) , (σσσσf)ult = 1,550 MPa (glass)

� From Table 2.2 � Em = 3.4 GPa (epoxy) , (σσσσm)ult = 72 MPa(epoxy)

� For the matrix ultimate failure strain (εεεεm)ult

� For the composite ultimate tensile strength (σσσσ1)ult

( ) ( )Answer 0.021ε

MPa 3400MPa 72

E

σ

ultmm

ultm ===

( ) ( )( ) ( )( )( )ultfmfultffult1 εEV-1σVσ +=


Lamina

� Example:

� Solution:

� For the Ultimate Tensile Strength of the Composite (σσσσ1)ult

� For the fiber ultimate failure strain (εεεεf)ult

( ) Answer MPa 03.361,1σult1 =

( ) ( )( ) ( )( )( )0.018MPa 34000.7-1MPa 1,5500.7σult1 +=

( ) ( )MPa 85,000

MPa 1,550

E

σ

ultf f

ultfε ==

( ) Answer 0.018εultf =

Coefficients of Thermal Expansion

� Major (composite)

Poisson’s Ratio (νννν12)

� Longitudinal Thermal

Expansion Coefficient (αααα1)

� Transverse Thermal

Expansion Coefficient (αααα2)

( )( )( ) ( )( )( )

1

mmmfff

E

VEαVEα

1α+

=

( )( )( ) ( )( )( ) ( )( )121mmmfff2 αVα1Vα1α ννν −+++=

( )( ) ( )( )mmff12 VV ννν +=

f = fiber m = matrix

1 = longitudinal

2 = transverse

αααα = linear thermal expansion coefficient, (m/m/OC)

νννν = poisson’s ratio, (unitless)

νννν12 = major (composite) poisson’s ratio, (unitless)

V = volume fraction,

(unitless)

E = elastic modulus, (Pa or

N/m2)


� Example:

� 5.) Base on Problem 1, for the glass/epoxy (70% fiber volume fraction) composite, find the major (composite) poison’s ratio

(νννν12). Determine the longitudinal (αααα1) and transverse (αααα2)thermal expansion coefficients.

� Solution:

� From Table 2.1 � Ef = 85 GPa (glass) , (ννννf) = 0.2 (glass) , (ααααf) = 5 x 10-6 m/m/OC (glass)

� From Table 2.2 � Em = 3.4 GPa (epoxy) , (ννννm) = 0.3 (epoxy) , (ααααm)= 63 x 10-6 m/m/OC (epoxy)

� E1 = 60.52 GPa (composite longitudinal elastic modulus �solved

in Problem 1)

� For the major (composite) poisson’s ratio (νννν12)

( )( ) ( )( )mmff12 VV ννν +=


� Example:

� Solution:

� For the major (composite) poisson’s ratio (νννν12)

� For the longitudinal thermal expansion coefficient (αααα1)

( )( ) ( )( ) ( )( ) ( )( )fmffmmff12 V-1VVV ννννν +=+=

( )( ) ( )( ) Answer 23.00.7-13.00.72.012 =+=ν

( )( )( ) ( )( )( ) ( )( )( ) ( )( )( )

1

fmmfff

1

mmmfff

E

V-1EαVEα

E

VEαVEα

1α++

==

( )( )( ) ( )( )( )Answer 10 x 5.98α

C0m

-6-6m6-

60.52

0.7-13.410 x 630.78510 x 5

1 == +


� Example:

� Solution:

� For the transverse thermal expansion coefficient (αααα2)

( )( )( ) ( )( )( ) ( )( )121fmmfff2 αV-1α1Vα1α ννν −+++=

Answer 10 x .472αC0

m

m-6

2 =

( )( )( ) ( )( )( ) ( )( )121mmmfff2 αVα1Vα1α ννν −+++=

( )( )( ) ( )( )( ) ( )( )23.010 x 5.980.7-110 x 633.010.710 x 52.01α -6-6-6

2 −+++=


� Increase in Fiber Volume Fraction � Longitudinal Thermal Expansion Coefficient becomes similar or equal with Transverse

Thermal Expansion Coefficient (αααα1 ≅ ≅ ≅ ≅ αααα2) � “Thermal Expansion Coefficient Stabilization”.

Coefficients of Moisture Expansion

� Longitudinal Moisture

Expansion Coefficient (ββββ1)

� Transverse Moisture

Expansion Coefficient (ββββ2)

( )( )( )( )( )m1

cmm

ρE

ρEβ

1β =

f = fiber m = matrix

1 = longitudinal

2 = transverse

ββββ = linear moisture expansion coefficient,

(m/m/kg/kg)

νννν = poisson’s ratio, (unitless)

νννν12 = major (composite) poisson’s ratio, (unitless)


E = elastic modulus, (Pa or

N/m2)

( )( )( )( ) ( )( )121ρ

ρβ1

2 ββm

cmm νν−=

+


� Example:

� 6.) Base on Problem 1, for the glass/epoxy (70% fiber volume

fraction) composite, find the longitudinal (ββββ1) and transverse (ββββ2) moisture expansion coefficients.

� Solution:

� From Table 2.2 � Em = 3.4 GPa (epoxy) , (ννννm) = 0.3 (epoxy) , (ββββm)= 0.33 m/m/kg/kg (epoxy)

� As solved in Problem 1 � E1 = 60.52 GPa (composite longitudinal

elastic modulus) , ρρρρm = 1,200 kg/m3 GPa (epoxy) , ρρρρc = 2,110 kg/m3 GPa (composite)

� As solved in Problem 5 � νννν12 = 0.23 (major composite poisson’sratio).

� For the longitudinal moisture expansion coefficient (ββββ1)

( )( )( )( )( )m1

cmm

ρE

ρEβ

1β =


� Example:

� Solution:

� For the longitudinal moisture expansion coefficient (ββββ1)

� For the transverse moisture expansion coefficient (ββββ2)

( )( )( )( )( ) Answer 0.033β

kgkg

mm

1,20060.52

2,1103.40.33

1 ==

( )( )( )( ) ( )( )121ρ

ρβ1

2 ββm

cmm νν−=

+

( )( )( )( ) ( )( ) Answer 0.7470.230.033β

kgkg

mm

1,200

2,1100.330.31

2 =−= +

Macro-mechanical Analysis

of a Lamina



Cum Fructo



Cum Laude


Elastic Moduli and Strain Energy

Stress at a Point� Resolve into � Normal

and Shear Components.

Stress Notation:

σx σxx σ11

σy σyy σ22

σz σzz σ33

ττττxy ττττ12 x �� 1

ττττyz ττττ23 y �� 2

ττττzx ττττ31 z �� 3


Stress at a Point� Shear stress

that are equal:

� ττττxy = ττττyx

� ττττxz = ττττzx

� ττττyz = ττττzy

Shear stress on 1 face of the cube

� 6 Stress components:

� 3 Shear Stress

� ττττxy

� ττττxz

� ττττyz

� 3 Normal Stress

� σσσσx

� σσσσy

� σσσσz


� Elastic Moduli (singular � Modulus)

� Elastic (Young’s / Flexural) Modulus (E)

� Shear (Rigidity) Modulus (G)

� Hooke’s Law Stress-Strain relationship for 3D Stress State

(condition) for Isotropic Material

xy

zx

yz

z

y

x

G1

G1

G1

E1

EE

EE1

E

EEE1

xy

zx

yz

z

y

x

τ

τ

τ

σ

σ

σ

00000

00000

00000

000

000

000

γ

γ

γ

ε

ε

ε

vv

vv

vv

−−

−−

−−

=

νννν = poisson’s ratio

σσσσ = normal stress

ττττ = shear stress

εεεε = strain

γγγγ = shear strain

E = elastic modulus

G = shear modulus

( )v+=

12EG

Recall:

ε

σE =


� Inverting Hooke’s Law Stress-Strain

relationship for 3D Stress State

(condition) for Isotropic Material

( )( )( ) ( )( ) ( )( )

( )( )( )

( )( ) ( )( )

( )( ) ( )( )( )

( )( )

xy

zx

yz

z

y

x

12-1

-1E

12-1E

12-1E

12-1E

12-1

-1E

12-1E

12-1E

12-1E

12-1

-1E

xy

zx

yz

z

y

x

γ

γ

γ

ε

ε

ε

G00000

0G0000

00G000

000

000

000

τ

τ

τ

σ

σ

σ

vv

v

vv

v

vv

v

vv

v

vv

v

vv

v

vv

v

vv

v

vv

v

+++

+++

+++

=

( ) γ

τ

v12EG ==+

Recall:


� Strain Energy (W) – energy needed to deform (shape

change) a body by the action of external forces.

� Strain Energy (W) due to 3D Stress

� Example:

� 1.) Stress analysis of a spacecraft structural member (isotropic

material, νννν = 0.3, E = 100 GPa, G = 60 GPa) gives the state of stress (see figure). Find the strain energy (W).

( ) ( )2

γτγτγτεσεσεσ xzxzyzyzxyxyzzyyxxW+++++

=

σσσσ = normal stress, (Pa or N/m2)

ττττ = shear stress , (Pa or N/m2)




� Example:

� Solution:

� Isotropic Material

� E = 100 GPa, G = 60 GPa, νννν = 0.3

� Stress Condition:

� σσσσx = 200 MPa , σσσσy = 100 MPa , σσσσz = -50 MPa

� ττττyz = 0 , ττττzx = 0 , ττττxy = -30 MPa (negative shear)

(-) = compressive

xy

zx

yz

z

y

x

G1

G1

G1

E1

EE

EE1

E

EEE1

xy

zx

yz

z

y

x

τ

τ

τ

σ

σ

σ

00000

00000

00000

000

000

000

γ

γ

γ

ε

ε

ε

vv

vv

vv

−−

−−

−−

=


RECALL:

� Sign convention for Shear Stress

� Basis � First Quadrant & Arrow direction

Postive (+) Negative (-)

(+ττττ) (-ττττ)


� Example:

� Solution:

� Isotropic Material

� E = 100 GPa, G = 60 GPa, νννν = 0.3

� Stress Condition:

� σσσσx = 200 MPa , σσσσy = 100 MPa , σσσσz = -50 MPa

� ττττyz = 0 , ττττzx = 0 , ττττxy = -30 MPa (negative shear)

(-) = compressive

30-

0

0

50-

100

200

00000

00000

00000

000

000

000

γ

γ

γ

ε

ε

ε

60,0001

60,0001

60,0001

100.0001

100,0003.0

100,0003.0

100,0003.0

100,0001

100,0003.0

100,0003.0

100,0003.0

100,0001

xy

zx

yz

z

y

x

−−

−−

−−

=

30-

0

0

50-

100

200

00000

00000

00000

000

000

000

γ

γ

γ

ε

ε

ε

60,0001

60,0001

60,0001

100.0001

100,0003.0

100,0003.0

100,0003.0

100,0001

100,0003.0

100,0003.0

100,0003.0

100,0001

xy

zx

yz

z

y

x

−−

−−

−−

=


� Example:

� Solution:

( )( ) ( )( ) ( )( ) ( )( ) ( )( ) ( )( )30-0000050100200ε100,000

0.3100,000

0.3100,000

1x +++−−+−+=

0.00185εx =

( )( ) ( )( ) ( )( ) ( )( ) ( )( ) ( )( )30-0000050100200ε100,000

0.3100,000

1100,000

0.3y +++−−++−=

0.00055εy =

( )( ) ( )( ) ( )( ) ( )( ) ( )( ) ( )( )30-0000050100200ε100,000

1100,000

0.3100,000

0.3z +++−+−+−=

0.0014εz −= (+) = extension (-) = contraction

30-

0

0

50-

100

200

00000

00000

00000

000

000

000

γ

γ

γ

ε

ε

ε

60,0001

60,0001

60,0001

100.0001

100,0003.0

100,0003.0

100,0003.0

100,0001

100,0003.0

100,0003.0

100,0003.0

100,0001

xy

zx

yz

z

y

x

−−

−−

−−

=


� Example:

� Solution:

( )( ) ( )( ) ( )( ) ( )( ) ( )( ) ( )( )30-000050-010002000γ60,000

1yz +++++=

0γyz =

0γzx =

0.0005γxy −=

( )( ) ( )( ) ( )( ) ( )( ) ( )( ) ( )( )30-000050-010002000γ60,000

1zx +++++=

( )( ) ( )( ) ( )( ) ( )( ) ( )( ) ( )( )30-000050-010002000γ60,000

1xy +++++=


� Example:

� Solution:

� Strain Energy

( ) ( )2

γτγτγτεσεσεσ xzxzyzyzxyxyzzyyxxW+++++

=

[ ][ ] [ ][ ] [ ][ ]( ) [ ][ ] [ ][ ] [ ][ ]( )2

0000-0.0005-30-0.0014-500.000551000.00185200W

+++++=

(-) = compressive

Answer MPa 255.0W =

Hooke’s Law for Different Types of

Materials� General 3D Stress-Strain Relationship

12

31

23

3

2

1

666564636261

565554535251

464544434241

363534333231

262524232221

161514131211

12

31

23

3

2

1

γ

γ

γ

ε

ε

ε

τ

τ

τ

σ

σ

σ

CCCCCC

CCCCCC

CCCCCC

CCCCCC

CCCCCC

CCCCCC

=

C = stiffness



εεεε = strain


C = E (Elastic Modulus)

Stiffness MatrixStiffness Matrix


Materials� Inverted General 3D Stress-Strain

Relationship

12

31

23

3

2

1

666564636261

565554535251

464544434241

363534333231

262524232221

161514131211

12

31

23

3

2

1

τ

τ

τ

σ

σ

σ

γ

γ

γ

ε

ε

ε

SSSSSS

SSSSSS

SSSSSS

SSSSSS

SSSSSS

SSSSSS

=

S = compliance



εεεε = strain


Compliance Matrix


Materials� Monoclinic Material – one plane

of symmetry

� Due to Symmetry some Stiffness(C) and Compliance (S) Constantsbecome ZERO.

� Stiffness Matrix [C] � Compliance Matrix [S]


Materials� Orthotropic Material – three

planes (perpendicular to each other) of symmetry.

� Due to Symmetry someStiffness (C) and Compliance(S) Constants become ZERO.

� Stiffness Matrix [C] � Compliance Matrix [S]

Hooke’s Law for a 2D Unidirectional

Lamina� Lamina – thin (small

thickness)

� Plane Stress – stresses at Direction 3 is small (can be neglected).

� 2D Stress-Strain Equations

� Reduced Stiffness Matrix [Q] � Compliance Matrix [S]

� Stress-Strain Relationship


Lamina� For the Reduced Stiffness

Matrix [Q]

� For the ComplianceMatrix [S]

νννν = poisson’s ratio

E = elastic modulus

G = shear modulus

1 = longitudinal

2 = transverse


Lamina

� Mechanical Properties of Uni-directional Lamina


Lamina

� Example:

� 2.) For a graphite/epoxy uni-directional lamina, find the following:

� Minor Poisson’s Ratio (νννν21)

� Compliance Matrix [S]

� Reduced Stiffness Matrix [Q]

� Strains in the 1-2 Coordinate System if the applied stress are � σσσσ1 = 2 MPa , σσσσ2 = -3 MPa(compressive) , ττττ12 = 4 MPa(+ shear)

Recall:

Major Poisson’s Ratio (νννν12)


Lamina

RECALL:

� Sign convention for Shear Stress

� Basis � First Quadrant & Arrow direction

Postive (+)

(+ττττ)

Negative (-)

(-ττττ)


Lamina

� Example:

� Solution:

� From Table 3.1 � E1 = 181 GPa , E2 = 10.3 GPa , G12 = 7.17

GPa , νννν12 = 0.28 (Major Poisson’s Ratio)

� For Minor Poisson’s Ratio (νννν21)

� For Compliance Matrix [S]


Lamina

� Example:

� Solution:

� From Table 3.1� E1 = 181 GPa , E2 = 10.3 GPa , G12 = 7.17 GPa , νννν12 = 0.28

� For Compliance Matrix [S]


Lamina

� Example:

� Solution:

� From Table 3.1 �

E1 = 181 GPa , E2

= 10.3 GPa , G12 =

7.17 GPa , νννν12 = 0.28

� For Reduced Stiffness Matrix [S]


Lamina

� Example:

� Solution:

� Strains in the 1-2 Coordinate System if the applied stress are

� σσσσ1 = 2 MPa , σσσσ2 = -3 MPa (compressive) , ττττ12 = 4 MPa (+ shear)


Lamina

� Example:

� Solution:

� Strains in the 1-2 Coordinate System if the applied stress

are � σσσσ1 = 2 MPa , σσσσ2 = -3 MPa (compressive) , ττττ12 = 4 MPa(+ shear)


Angle Lamina

� Local (Material) Axes �

1-2 Coordinate System

� Direction 1 � fiber direction (longitudinal)

� Direction 2 �

perpendicular to fiber direction (transverse)

� Global (Composite) Axes� x-y Coordinate System (off-axes with 1-2 Coordinate System)

� θθθθ � angle between the 2 coordinate system


Angle Lamina

� Global Stresses

(σσσσ and ττττ)

� Local Stresses


� Inverse TransformationMatrix [T]-1

c = cos θ s = sin θ

� Stress Equations


Angle Lamina

� Global Stresses


� Local

Strains (εεεεand γγγγ)

� Reduced Stiffness Matrix [Q]

� Stress-Strain Equations


Angle Lamina

� Global Strains

(εεεε and γγγγ)

� Local

Strains (εεεεand γγγγ)

� Reuter Matrix [R]

� Strain Equations

� Inverse ReuterMatrix [R]-1


� Transformation Matrix [T]


Angle Lamina

� Global Strains


� Global

Stress (σσσσand ττττ)

� Global Stress-Strain Equations

� Reduced Stiffness Matrix (Angle Lamina)[ ]Q


Angle Lamina

� Global Strains


� Global

Stress (σσσσand ττττ)

� Global Stress-Strain Equations

� Compliance Matrix (Angle Lamina) [ ]S


Angle Lamina

� For the Reduced StiffnessMatrix (Angle Lamina)[ ]Q



Angle Lamina



Engineering Constants for an Angle

Lamina

� Angle Lamina Matrix (Engineering Constants)

Invariant Form of Stiffness and Compliance

Matrices for an Angle Lamina

� For the Reduced StiffnessMatrix (Angle Lamina) [ ]Q

� Invariants:

Invariant Form of Stiffness and Compliance

Matrices for an Angle Lamina


� Invariants:

Strength Failure Theories of an Angle

Lamina

� Comparison of stress condition of the material to Failure

Criteria (bases of decision).

� Laminate Strength � related to individual lamina strength.

� Failure Criteria – based on Normal (tension or

compression) and Shear strengths of Uni-directional

Lamina.

� Maximum Stress Failure Theory – resolve applied stresses (x-y Coordinate System) into normal and shearbase on local (material) axes (1-2 Coordinate System).

� Normal or Shear stress (base on local / material axes) equal

or exceed (more than) ultimate strength of uni-directional

lamina � Failure Occurs (Lamina Fails).


Lamina

� Failure Criteria

� Maximum Stress Failure Theory


Lamina

� Failure Criteria

� Maximum Strain Failure Theory – applied strains (x-yCoordinate System) are resolved to strains (normal and shear)in local (material) axes (1-2 Coordinate System).

� Normal (longitudinal & transverse) or Shear (in-plane) strains

(base on local / material axes) equal or exceed (more than)

ultimate strain of uni-directional lamina � Failure Occurs

(Lamina Fails).

Hygrothermal Stresses and Strains in a

Lamina

� Unidirectional Lamina

� Stress-StrainRelationship due to Temperature and Moisture

� Inverted Stress-StrainRelationship due to Temperature and Moisture

� T = temperature

� C = moisture

Hygrothermal Stresses and Strains in a

Lamina� Unidirectional Lamina

� Thermally (temperature) induced Strains – only at the longitudinal(direction 1) and transverse (direction 2). NO SHEAR STRAIN.

� αααα = thermal expansion coefficient, (m/m/OC)

� Moisture induced Strains – only at the longitudinal (direction 1) and transverse (direction 2). NO SHEAR STRAIN.

� ββββ = moisture expansion coefficient, (m/m/kg/kg)

� ∆∆∆∆ = change (difference)

Macro-mechanical Analysis

of Laminate



Cum Fructo



Cum Laude


Laminate Code

� Laminate – bonded layers

of Lamina

� Laminate Code – special

notation for identification of

each lamina layer :

� By Location

� By Material (fiber) Type

� By Orientation Angle of Fibers

� Slash sign – separation of one ply to another ply.

Laminate Code

� Laminate Code

� [ 0 / -45 / 90 / 60 / 30 ]� 5 plies (laminas)

� Each ply � same thickness and material type

� Each ply has different fiber orientation

� [ 0 / -45 / 902 / 60 / 0 ]� 6 plies (laminas)

� 902 � two 90O adjacent (neighboring) plies

� Each ply has different fiber orientation

(+) angle = counterclockwise

(-) angle = clockwise

Laminate Code

� Laminate Code� [ 0 / -45 / 60 ]S

� 6 plies (laminas)

� S � symmetric laminate (repeated in reverse order).� Plies above mid-plane has same

orientation, material type, and thickness as the plies below the mid-plane.

� Each ply has different fiber orientation.

� [ 0 / -45 / 60 ]S


� S and 60 � symmetry (repeated in reverse order) at mid-surface

� Each ply has different fiber orientation.



Laminate Code

� Laminate Code

� [ 0Gr / ± ± ± ±45B ]S


� S � symmetric laminate

(repeated in reverse order).

� Plies above mid-plane has

same orientation, material type, and thickness as the

plies below the mid-plane.

� 0O plies � graphite/epoxy

� ±±±±45O plies � boron/epoxy

� ±±±±45 � +45O angle ply followed by -45O angle ply.

� Each ply has different fiber

orientation.



Stress-Strain Relations for a Laminate

� Stress-Strain Relation � simple (axial)

loading.

� Normal Stress (σσσσx) �

� Normal Strain (εεεεx) �

F = force, (N)

A = cross-sectional

area, (m2)

E = elastic modulus,

(Pa or N/m2)

⊥⊥⊥⊥ = perpendicular


� Stress-Strain Relation � pure bending

moment (M).

� Strain at distance z from centroidal (centroid)

line (εεεε xx)

� Stress base on centroidal distance (σσσσxx)z = centroidal

distance, (m)

ρρρρ = curvature radius, (m)

M = moment, (N-m)

I = second moment

of inertia, (m4)

E = elastic

modulus, (Pa or

N/m2)


� Stress-Strain Relation � simple (axial) loading and

bending moment (M).

� Strain (εεεε xx)z = centroidal

distance, (m)

ρρρρ = curvature radius, (m)

κκκκ = curvature, (1/m)

M = moment, (N-m)

I = second moment

of inertia, (m4)

E = elastic

modulus, (Pa or

N/m2)

In-Plane and Flexural Modulus for a

Laminate

� Laminate Stiffness

� Where:

N = load, (N)

M = moment, (N-m)

[A] = extensional

stiffness matrix

[B] = coupling

stiffness matrix

[D] = bending

stiffness matrix


εεεε0 = strain at mid-plane [ z = 0 ],

(unitless)

In-Plane and Flexural Modulus for a

Laminate

� Inverted Laminate Stiffness

� Where:

N = load, (N)

M = moment, (N-m)

[A*] = extensional

compliance matrix

[B*] = coupling

compliance matrix

[D*] = bending

compliance matrix


εεεε0 = strain at mid-plane [ z = 0 ],

(unitless)

[ ]T = transposition

matrix operation

[ ]-1 = inverse

matrix operation

Hygrothermal Effects in a Laminate

� Hygrothermal Strains – Mechanical Strains due to combined effect of Thermal and Moisture (Hygrothermal).

� Hygrothermal Stress – combined effect of Thermal and Moisture (Hygrothermal).

σσσσ = stress, (Pa or N/m2)




Q = reduced

stiffness

T = free expansion

thermal strain

C = free expansion

moisture strain

M = mechanical

strain

Manufacturing



Cum Fructo



Cum Laude


Manufacturing Processes Of

Composites

� Structural applications � most designers depend on traditional materials :� Steel� Aluminum

� REASON � Composite Materials are expensive (high production cost).

� SOLUTION � General movement by Composites Industry towards :� Use of less expensive fibers � graphite fiber and

aramid fiber� Boron fiber � very costly

� Reduce processing (manufacturing) cost of Composite Materials.

Manufacturing Goals

� Objectives (goals) in Composite Material Production

(manufacturing) :

� Assemble Fibers

� Impregnate (put) Matrix

� Resin � thermoset for PMC

� Thermoplastic � for PMC

� Ceramic � for CMC

� Metal (molten / liquid state) � for MMC

� Shape of the Product (according to designed)

� Curing of Matrix

� Resin � solidification by thermo-chemical hardening.

� Chemical Reaction + Heating (speed-up chemical reaction).

� Thermoplastic, Ceramic, Metal � solidification by cooling.

Polymer � thermoset or thermoplastic

Manufacturing Process

� 2 Main Steps in Manufacturing Operations:

� Lay–up � arrangement

� For Lamina � arranging the fiber reinforcements before applying the matrix.

� For Laminate � arranging the laminas to form a laminate.

� Shaping the laminate to make the desired part.

� Curing � drying (resin, ceramic) and hardening (polymer, ceramic, metal) of the matrix of a finished composite.

� Can be:

� Unaided (natural / gradual)

� application of Heat and/or Pressure

� 3 Main Groups of Lay-up Operation:

A. Winding and Laying operations

B. Molding (open & close) operations

C. Continuous lamination

Winding and Laying Operation

� Filament Winding - continuous filaments (fibers) wound

(lay-up) onto mandrel (shape guide).

� Common application � production of pressure tanks.

Winding Types

Winding and Laying Operation� Filament Winding

Characteristics

� The filament (or tape, tow or roving, or band) is either pre-coated with the polymer or is drawn through a polymer bath(wet filament winding) so that it picks up polymer on its way to the winder.

� Void volume can be higher (3%).

� Productivity is high (50 kg/hr).

� Applications include fabrication of:

� Composite pipes, tanks, and pressure vessels.

� Carbon fiber reinforced rocket motor cases used for Space Shuttle and other rockets are made this way.

Winding and Laying Operation� Filament Winding – also called Wet Filament Winding

because fibers pass through a matrix bath.

� Highly automated

� low manufacturing costs if high throughput

� Common Products � glass fiber pipe, sailboard masts(vertical support or pole).

Winding and Laying Operation� Filament Winding

� Primarily used for hollow, circular or oval components (parts)

�pipes and tanks (ex. pressure tanks).

� Fiber tows (rovings) pass through a resin (for thermoset) or molten

thermoplastic bath and then wound (lay-up) onto a mandrel (shape

guide) which is being rotated at a controlled rate.

� Fibers are wound in a variety of orientations controlled by a fiber

feeding mechanism.

Winding and Laying Operation

� Filament Winding Process� Fibers pass through a liquid

resin (for thermoset) or molten thermoplastic.

� Fibers are wound (lay-up) on a mandrel (shape guide).

� After lay–up is completed, the composite is cured on the mandrel.� Curing is done by heating

for chemical reaction for thermosetting or to melt the thermoplastic for distribution uniformity and good impregnation with the fibers to minimize voids.

� The mandrel is then removedby melting, dissolving, breaking–out or some other method.

Open Mold Operations

� Hand Lay-up (contact molding) - the oldest and simplest way of making

fiberglass–resin (for thermoset) or fiberglass-thermoplastic composites.

� Gel Coat – for best (smooth) surface quality.

� Mold release agent (silicone, polyvinyl alcohol, fluorocarbon, or

sometimes, plastic film) is applied (placed) first.

� Applications are standard wind turbine blades, boats, etc.


� Hand Lay-up (contact molding) - all shapes can be produced.

� The resin (for thermoset) or molten polymer and fiber are placed manually.

� Air is expelled by squeezing (by pressing) if necessary. Multiple layers of fibers can be placed.

� Hardening is at room temperature (or speed-up by heating).

� Void volume is typically 1%.

� Foam cores may be used for greater shape complexity.

� Process is slow (deposition rate around 1 kg/hr) and labor-intensive.

� Quality is highly dependent on operator skill.

� Extensively used for products such as airframe components, boats, truck bodies, tanks, swimming pools, and ducts (centralized air-conditioning system).


� Hand Lay-up (contact molding) Process

� Resins (for thermoset) or molten thermoplastic are impregnated manually (using rotating roller [nip-roller] or brushes) into the fibers (woven, knitted, stitched or bonded fabrics or textile).

� Nip-roller or brush force resin or molten thermoplastic bath into the fabrics (textile).

� Laminates are left to cure under standard atmospheric conditions (or by heating to speed-up curing).


� Spray Lay-up

� A spray gun supplying resin in two converging streams into which roving is chopped.

� Automation with robots results in highly reproducible production.

� Labor costs are lower.


� Spray Lay-up Process

� Chopped fibers and resins are sprayed simultaneously into or onto the mold.

� Applications are lightly loaded structural panels like caravan bodies, truck fairings (streamlined structures to reduce air drug or friction), bath tubes, small boats, etc.


� Vacuum-Bag Molding

� For making a variety (different kinds) of components, including relatively large parts with complex shapes.

� Applications are large cruising boats, racecar components, etc.


� Vacuum-Bag Molding

� Pressure is applied to the laminate once laid-up in order to improve its consolidation (compacting to minimize voids) �done by sealing the plastic film.

� Air inside the bag (plastic fim) is extracted by a vacuum pump.

� Up to one atmosphere of pressure can be applied to the laminate to consolidate (compact) it.


� Vacuum-Bag Molding Process� Fibers together with

resin (for thermoset) or molten thermoplastic is placed inside a vacuum bagging film and sealedwith a sealant tape.

� Heat is applied to keepthe thermoplastic in molten state or to speed-up chemical reaction of resin.

� The vacuum bagging filmis connected to a vacuum pump for air suction creating a vacuum condition. Vacuum level is controlled by monitoring the vacuum gage.

Open Mold Operations� Pressure-Bag Molding

� A reverse process (inflating) of vacuum–bag molding.

� Applications are sonar domes, antenna housings, aircraft fairings

(streamlined structures to reduce air drug or friction), etc.


� Pressure-Bag Molding Process� Fibers together with

resin (for thermoset) or molten thermoplastic is placed inside a pressure bagging film and sealedwith a sealant tape.

� Heat is applied to keep the thermoplastic in molten state or to speed-up chemical reaction of resin.

� Compressed air is blown on the pressure bagging film so that it presses and compressesthe fibers and the resin or molten thermoplasticcontained inside it.


� Thermal Expansion Molding

� Prepeg or Fibers together with resin (for thermoset) or molten thermoplastic are wrapped around rubber blocks, and then placed in a metal mold.

� As the entire assembly is heated, the rubber expands more than the metal, putting pressure on the laminate.

� Complex shapes can be made reducing the need for joining and fastening operations.

Open Mold Operations� Autoclave Molding

� Similar to both vacuum–bag and pressure–bag molding.

� Applications are lighter, faster and more agile (fast moving) fighter aircraft, motor sport vehicles.

Open Mold Operations� Autoclave and Vacuum-Bag Molding

� Most parts made by hand lay-up or automated tape lay-up must be

cured by a combination of heat, pressure, vacuum, and inert

atmosphere (inert gas environment).

� To achieve proper cure, the part is placed into a plastic bag inside an

autoclave.

Open Mold Operations� Autoclave and Vacuum-Bag Molding

� A vacuum is applied to the bag to remove air and volatile products.

� Inside the autoclave, heat and pressure are applied for curing.

Usually an inert gas (Argon, Neon, Xenon, Krypton) is provided inside

the autoclave or by introduction of nitrogen or carbon dioxide

(prevent other chemical reaction to occur like oxidation) which is

cheaper than inert gas.

� Exothermal reaction (chemical reaction that produces heat) may

occur if the curing step is not done properly.

Same process for

Autoclave and Pressure-

Bag Molding only that

compressed air is used.


� Centrifugal casting

� used to form round objects such as pipes, cylinder liner.

� Composite is placed in a rotating mold. Compaction (consolidation) is by the action of centrifugal force.

Open Mold Operations� Centrifugal Casting Process

� Fibers are placed inside the mold. The mold is then rotated and the molten matrix is placed inside the mold using a ladle and a spout.

� Heat is applied to the rotating mold to keep the matrix in molten statefor uniform distribution throughout the fibers.

� Mold rotation uniformly distributes the matrix to the fibers.

� Fiber and matrix consolidation (compaction) is through the action of centrifugal force (due to mold rotation).

Mould

Release

agent Fibers

spout

Ladle

Matrix

liquid matrix flow


� Centrifugal Casting

Open Mold Operations� Semi-centrifugal Casting

� Fibers and molten Matrix are placed inside the mold.

� The mold is closed and bolted on a revolving table.

� Mold rotation uniformly distributes the matrix to the fibers.

� Fiber and matrix consolidation (compaction) is through the action of

centrifugal force (due to mold rotation).

Open Mold Operations� Centrifuge Casting

� Fibers are placed inside the mold.

� Molten matrix pass through a rotating runner.

� Runner rotation uniformly distributes the matrix to the fibers.

� Fiber and matrix consolidation (compaction) is through impact

action of matrix to the fibers (due to centrifugal force cause by

rotating runner).

Open Mold Operations� Continuous Pultrusion

� Make straight products that have the same volume all along their lengths.

� The equivalent of metal extrusion.

� Complex parts can be made.


� Continuous Pultrusion

� Two dimensional shapes including solid rods, profiles, or hollow tubes similar to those produced by extrusion, can be made, hence its name “pultrusion”.



� Production rates around 1 meter / min.

� Applications are:

� Sporting goods (golf club shafts)

� Vehicle drive shafts (because of high damping [vibration

absorption] capacity)

� Non-conductive ladder rails (electrical service)

� Structural members for vehicle and aerospace applications.



� Continuous Fibers are pulled through the matrix melt bath then pelletized (small dimension compressed material) according to the desired size.

� The process results to fibers completely surrounded by matrix.

Open Mold Operations� Continuous Pultrusion Process

� Continuous Fibers (roving strands) positioned by guides are pulled from

a creel through a matrix bath and then on through a heated die (gives

shape or shape guide).

� The die completes the impregnation of matrix to the fiber, controls the

matrix content and cures (heating) the material into its final shape as it

passes through the die.

� Emerging product is cooled and pulled by oscillating clamps then

automatically cut to length (pelletized).

� Small diameter products are wound up.


� All fibers are evenly spaced and completely surrounded (covered) by

matrix.

� Key Advantages – "Fiber Skeleton" inside the part leads to:

� High impact properties

� Lower creep tendency

� Lower warpage (twisting) problems

� Higher heat deflection temperature (HDT) - deflection (deformation) occurs at higher temperature (dimension stability)


� Other Advantages:

� Advantages of Pultrusion Long Fiber

Pellets vs. Short Fiber

� Higher mechanical properties

combined with significantly higher

impact strength

� Reduced creep tendency

� Lower warpage (twist) and better

dimensional stability

� Advantages of Pultrusion Long Fiber

Pellets vs. Wire Coating Long Fibers

� More homogeneous fiber distribution

� Higher impact strength

� Better surface / part appearance

� Lower wear on cylinder and tool

(machine use to produce pellets)

Pultrusion Pellet –

Uniform fiber distribution

surrounded by matrix

throughout the whole

pellet.


� Pulforming

� Similar in process with pultrusion in many ways.

� Capable of making straight or curved products with changing

shapes and volumes along the product length.

� Typical pulformed product � curved reinforced plastic car spring

(shown in figure).

Close Mold Operations� Matched-die Molding -

consists of closely matched male and female dies (shape

guide).

� Applications are spacecraft parts, toys, etc.

Close Mold Operations

� Compression Molding – by compression the composite

material (Sheet Molding Compound [SMC] or Bulk Molding

Compound [BMC] ) takes the shape of the mold.

� Pressure and Heat (using hot hydraulic press) is appliedduring the molding process.


� Injection Molding – closed process (mold is closed).

� Used in PMC processes.

� Applications are auto parts, vanes, engine cowling (cover) defrosters and aircraft radomes (dome-shaped radar housing).

Close Mold Operations� Injection Molding Process

� Injection process begins with a thermosetting material (or sometimes thermoplastic) outside the mold (feed into the hopper).

� Polymer matrix (may contain reinforcements or not) is first softened by heating and mechanical working (with an extrusion–type screw) inside the barrel.

� Polymer matrix is then forced (using screw-type extruder) under high pressure from a ram or screw, into the cool mold (water-jacketed).


� Resin Transfer Molding (RTM)

� Low-pressure (50 – 100 psi) molding process.

� Uses resin (thermoset) as matrix.

� Used when parts with two smooth surfaces are required.


� Resin Transfer Molding (RTM)� Requires a resin viscosity of 200 to 600 centipoise (since

RTM is a low-pressure molding process).� Multi-compatible with a variety of resin systems.� Resin types:

� Modified acrylic and hybrid resins (polyester and urethane)

� Epoxy

� Polyester

� Vinyl Esters

� Phenolic


� Resin Transfer Molding (RTM) Process

� Dry Fiber reinforcement fabric (mat / pre-form / textile / woven / hybrid) is laid by hand into a mold.

� Mold is closed and resin mixture is injected into the mold cavity.

� Resin curing is done under heat and pressure.



� Advantages:

� Lower chemical fumes emissions (since close mold) thanopen mold processes (spray-up or hand lay up).

� High quality finish surface (like those on an automobile).

� Produce parts faster (5 –20 times faster than open molding techniques).

� Produces product of tighter dimensional tolerances (± .005 inch).

� Complex mold shapes can be achieved.

� Cabling and other fittings can be incorporated into the mold designs.



� Disadvantages:

� High production volumes is required to offset high tooling costs (open molding techniques is cheaper).

� Only limited amount of reinforcement materials due to the flow and resin saturation of the fibers (more fibers, difficult for resins to flow through because RTM is low-pressure molding process).

� Part size to be produced is limited by the mold.


� Vacuum Assisted Resin Transfer Molding (VARTM)

� Similar in process with Resin Transfer Molding (RTM).

� Vacuum is used to enhance the resin flow and reduce voidformation.

� Resin is injected at high pressure.

Close Mold Operations� Vacuum Assisted Resin Transfer Molding (VARTM) Process

� Dry Fiber reinforcement fabric (mat / pre-form / textile / woven / hybrid)

is laid by hand into a mold.

� Mold is closed and resin mixture is injected into the mold cavity.

� Vacuum sucks out air to reduce void formation, enhance the resin

flow, and thorough (complete) impregnation (wetting) of resin to fibers.

� Resin curing is done under heat and pressure.

Continuous Lamination

� Sheet Molding Compound (SMC)

� Used for compression molding process (hot hydraulic press).

� Matrix � polyester resin, vinyl ester resin



� Types of SMC:

� SMC – R � randomly oriented discontinuous fibers.

� SMC – CR � containing a layer of unidirectional continuous fibers

together with randomly oriented discontinuous fibers.

� XMC � containing continuous fibers arranged in an X pattern

together with randomly oriented discontinuous fibers.



� Chopped glass fibers are added to polyester or vinyl esterresin mixture.


� Prepeg – ready-made tape compose of uni-directional

continuous fibers (commonly carbon, glass, and aramid)

which is pre-impregnate with a partially cured polymer

matrix (thermoset or thermoplastic).

� Composite Form most widely used for structural applications.

� Matrix content is between 35% to 45% by volume.

� Wound on spools

� Standard width � 25 mm. to 1,525 mm.

� Standard thickness � 0.08 mm. to 0.25 mm.


� Prepeg

� Storage Temperature:

� For thermoplastic matrix � room temperature

� For thermoset (resin) matrix � 0OC or lower temperature

(slow down curing due to chemical reaction).

� Storage (Shelf) Life:

� For thermoplastic matrix � indefinite time (aviod UV or

other chemical exposure).

� For thermoset (resin) matrix � only 6 months (very small

curing chemical reaction starts even at very low temperature).

Continuous Lamination� Prepegs

� Application on Structure Fabrication

� By Lay-up operation prepeg tapes are molded according to desired shape (structure).

� Several prepeg tape layers are used to achieve desired thickness.

� Prepreg tape is wrapped in 2 directions or spiral wrapped.

� During curing no additional matrix (thermoplastic or thermoset) is needed.

� Typical curing condition (melting the thermoplastic for homogeneous distribution or curing the thermoset) is at 120OC-200OC and 100 psi (pressure for compaction to minimize viods) in autoclave.

� Commonly for Tubular Products

� Fishing rods (for fishing)

� Golf clubs

� Oars (for rowing boat)

Continuous Lamination� Prepeg Process

� Several rows of uni-directional continuous fiber rovings(untwisted fiber strands or bundles) passes through a polymer bath (molten thermoplastic or thermoset resin).

Collimator � fiber guide


� Or uni-directional continuous fiber rovings (untwisted fiber strands

or bundles) are sandwiched between release paper (coated with

a thin film of molten thermoplastic or thermset resin) and a carrier

paper (prevent prepegs from sticking with each other when wound

on spool).


� Impregnated fibers, sandwiched between release paper and carrier paper, are pressed by heated rollers (calendering) to partially cure (thermoset matrix) or uniform distribution (thermoplastic matrix).


� Final prepreg product is a thin tape consisting of continuous and aligned fibers embedded in a thermoplastic or partially cured resin.

� Prepegs are winding onto a cardboard core.

Boron/epoxy

prepeg tape

Metal Matrix Composites

(MMC)



Cum Fructo



Cum Laude


Definition and Composition

� Metal Matrix Composite (MMC) – consisting of a metallic matrix combined with a ceramic (oxides, carbides) or metallic(lead, tungsten, molybdenum) reinforcement (dispersed phase).

� Also known as Fiber-Reinforced Metal Matrix Composite

(FRMMC).

� Combine the high tensile strength and elastic modulus of a fiber

(reinforcement) with metals (matrix) of low density � results to

good strength-to-weight ratio (specific strength) and modulus-to-

weight ratio (specific modulus) of the MMC.

MMC cross-section

Definition and Composition

� Metal Matrix Composite (MMC)

� Expensive and are only use where improved properties and performance can justify the added cost.

� Applications are mostly in aircraft components, space systems, and high-end sports equipment.

� Scope (range) of applications will increase as manufacturing costs

are reduced.

Aluminum

reinforced with

Silicon Carbide

particles

Advantage and Disadvantage

� Advantages:

� Better wear resistance.

� Do not absorb moisture.

� Fire and radiation resistant.

� Wider operating temperature range.

� Do not display outgassing (release of trapped gases).

� Better properties at elevated temperature.

� Disadvantages:

� Expensive

� Heavy (metal matrix).

� Less toughness

� Difficult to fabricate (manufacture or process).

� Limited available experience in application (since expensive).

Mechanical Properties

� Better electrical (for electrically conductive reinforcement)

and thermal (for heat conductive reinforcement)

conductivity.

� Higher specific modulus (modulus-to-weight ratio) and specific strength (strength-to-weight ratio).

� Lower thermal expansion coefficient (CTE) than metals

(minimal expansion at higher temperature).

� Higher thermal deformation (deflection) resistance.

� Improvement in stiffness (higher elastic modulus).

� Strength (reinforcement) and ductility (matrix).

� Creep and Fatigue resistance.


� MMC has reduced Thermal Conductivity.

� Depends on the fiber thermal conductivity.


� MMC has lower thermal

expansion coefficient(CTE) than metals.


� MMC has improved Stiffness (Elastic Modulus).

� Fiber Length

� Fiber Volume Fraction


� MMC has improved Stiffness (Elastic Modulus).

� Wider range of Operating Temperature

Reinforcing Materials

� Types of Reinforcing materials

� Common reinforcement (reinforcing phase) are:

� Particles

� Metal

� Ceramic (usually cerments � cemented carbides)

� Fibers (Short [whiskers] or Continuous [long]) �various materials including other metals.

� Ceramic

� Carbon

� Boron

Metallic Binders

� Cemented carbide – composed of one or more carbide

compounds bonded in a metallic matrix.

� Common cemented carbides:

� Tungsten carbide (WC)

� Titanium carbide (TiC)

� Chromium carbide (Cr3C2)

� Tantalum carbide (TaC)

� Principal Metallic Binders are:

� Cobalt � used for Tungsten Carbide (WC)

� Nickel � used Titanium Carbide (TiC) and Chromium Carbide (Cr3C2)

Types of Metal Matrix Composites

� Metal Matrix Composites (MMC) Types:

� Aluminum Matrix Composite (AMC)

� Magnesium Matrix Composite

� Titanium Matrix Composite

� Copper Matrix Composite


� Common metal matrix composite (MMC).

� Usually based on Aluminum-Silicon (Al-Si) alloys and on the alloys of 2xxx and 6xxx series (ASME alloy codes).

� Properties:

� High strength even at elevated temperatures

� High stiffness (elastic modulus)



� Properties:

� Low density (light weight)

� High thermal conductivity

� Excellent abrasion resistance

� Reinforcement:

� Alumina (Al2O3) or Silicon Carbide (SiC) particles (Particulate

Composite) in amounts 15%-70% Volume Fraction.

� Continuous Fibers of Alumina, Silicon Carbide (SiC), Graphite

(Long-Fiber Reinforced Composites).

� Discontinuous Fibers (Short Fibers or Whiskers) of Alumina

(Short-Fiber Reinforced Composites).



� Manufacturing (fabrication) methods:

� Powder metallurgy (sintering � bond [fuse] metal particles by applying pressure and heat below melting temperature).

� Stir Casting � discontinuous (short or whiskers) reinforcement is stirred (for uniform distribution) into a molten metal which is allowed to solidify in a mold.

� Infiltration (vapor deposition) � fiber is passed through a thick cloud of vaporized metal, coating it.

� Applications:

� Automotive parts (pistons, pushrods, brake components).

� Brake rotors for high speed trains.

� Bicycle Frame and Golf clubs.

� Electronic substrates (semi-conductor due to Silicon) and Coresfor high voltage electrical cables.


� Magnesium Matrix Composite

� Properties:



� High wear resistance

� Good strength even at elevated temperatures

� Good creep resistance

� Reinforcement:

� Mainly by Silicon Carbide (SiC) particles (particulate composite).

� Applications:

� Components for racing cars.

� Lightweight automotive brake system.

� Aircraft parts (gearboxes, transmissions, compressors and engine).



� Properties:

� High strength


� High creep resistance

� High thermal stability

� High wear resistance

� Reinforcement:

� Continuous monofilament (not strand or bundle) Silicon Carbide (SiC) Fiber (long-fiber reinforced composite).

� Titanium Boride (TiB2) and Titanium Carbide (TiC)particles (particulate composite).




� Powder metallurgy (sintering � bond [fuse] metal particles

by applying pressure and heat below melting temperature).

� Applications:

� Structural components of F-16 jet plane landing gear.

� Turbine engine components (fan blades, actuator pistons,

synchronization rings, connecting links, shafts, discs).

� Automotive engine components (drive train parts and general machine components).



� Properties:

� Low thermal expansion coefficient


� Good electrical conductivity (due to copper matrix)

� High thermal conductivity

� Good wear resistance

� Reinforcement:

� Continuous Carbon Fibers (C), Silicon Carbide (SiC),

Tungsten (W), Stainless Steel 304 (long-fiber reinforced

composite).

� Silicon Carbide (SiC) particles (particulate composite).




� Powder metallurgy (sintering � bond [fuse] metal particles

by applying pressure and heat below melting temperature).

� Infiltration (vapor deposition) � fiber is passed through a

thick cloud of vaporized metal, coating it.

� Applications:

� Electronic relays.

� Electrically conducting springs.

� Other electrical and electronic components.

MMC Processing (Manufacturing)

� 3 types of MMC manufacturing (processing):

� Solid State Method

� Liquid State Method

� Vapor Deposition Method

� SOLID STATE METHOD � for large surface areacomposite, matrix is particle or foil form (matrix in solid form).

� Powder Metallurgy � powder (particles) blending and consolidation (compaction).

� Powdered metal and discontinuous reinforcement are mixed and then bonded through a process of compaction, degassing (gas removal), and thermo-mechanical treatment (hot pressing or extrusion).

MMC Processing

(Manufacturing)

� SOLID STATE METHOD

� Diffusion Bonding

� Layers of metal foil are

sandwiched with long

fibers, and then pressed

(heat + pressure) through

to form a matrix (metal

foil).

� Ex. Ti, Ni, Cu, Al

reinforced with Boron


� LIQUID STATE METHOD � matrix is in liquid(molten) form.� Electroplating / Electroforming

� Solution containing metal ions loaded with reinforcing particles is co-deposited (by electroplating or electroforming through passage of electricity) forming a composite material.

� Stir Casting

� Discontinuous reinforcement is stirred into molten metal, which is allowed to solidify.

� Reactive processing

� Chemical reaction occurs, one of the reactants forms the matrix and the other the reinforcement.


� LIQUID STATE

METHOD

� Spray deposition

� Molten metal is

sprayed onto

continuous fibers

or particles.


� LIQUID STATE

METHOD

� Squeeze Casting

� Molten metal is

injected into a

form (mold) with

fibers already

placed inside it.

� Ram squeezes

the molten metal

and fibers for

consolidation

(compaction).


� LIQUID STATE METHOD

� Liquid Melt Infiltration

� (a) � Fibers are placed inside a mold

(die).

� (b) � The mold is closed and air is

evacuated (removed).

� (c) � Gas pressure is applied to inject

the molten metal into the mold.


� VAPOR DEPOSITION METHOD � matrix is

in vapor form.

� Physical Vapor Deposition

� Fiber passed through a thick cloud of vaporized

metal which coats it (fiber).

Applications of MMC

� Applications of different types of MMC

Applications of MMC

� Mid-fuselage (aircraft body) structure of Space Shuttle Orbitershowing Boron-Aluminum tubes.

� Cast Aluminum-SiCmulti-inlet fitting for a

truss node.

Applications of MMC

� Aerospace Applications

of MMC

Applications of MMC

� Cutting Tools � common application of Cemented

Carbides (usually Tungsten Carbide).

� Carbide drills � made from tough cobalt matrix with hard tungsten carbide particles.

� Titanium carbide cermets � for high temperature applications.

� Cutting tool material for machining steels.

� Nickel is the preferred binder (superior oxidation resistance at

high temperature than cobalt).

� Tank Armors � steel reinforced with boron nitride.

� Boron nitride � good reinforcement for steel.

� Very stiff (high elastic modulus) and does not dissolve in

molten steel.

Applications of MMC

� Rotor Blade � aluminum MMC

� Automotive disc brakes

� Carbon Fiber with Silicon Carbide matrix (for high specific heat and thermal conductivity).

� Modern high-performance sport cars (ex. Porsche)

� Disc Brake Calipers

� Aluminum Matrix Composites (AMC)

� Weigh reduction as much as 50%.

� Increase in stiffness.

� Driveshaft (Ford racing cars) � aluminum boron carbide MMC.

� Increase in driveshaft critical speed by reducing inertia.

� Driveshaft top speed is increased beyond safe operating speedwhen using standard aluminum.

Applications of MMC

� Cylinder Liners (in Honda) � aluminum metal matrix

composite in engines.

� Honda engines � B21A1, H22A, H23A, F20C, F22C, and C32B.

� Toyota engine � 2ZZ-GE.

� Cylinder Sleeves (Porsche Boxster and 911).

� F-16 (Fighting Falcon) landing gear � monofilamentSilicon Carbide Fibers in a Titanium matrix.

� Bicycle Frames � aluminum MMC.

Ceramic Matrix Composites (CMC)

and

Carbon-Carbon Composites (CC)



Cum Fructo



Cum Laude


Ceramic Matrix Composites

(CMC)



Cum Fructo



Cum Laude


Ceramic Matrix Composites

� Ceramic Matrix Composite (CMC) �consisting of a ceramic matrix combined with a ceramic (oxides, carbides) in dispersed phase(fibers).

� Ceramic Matrix Composite (CMC) is designed to

improve toughness of conventional ceramic (main

disadvantage is brittleness).

� CMC are produced by conventional ceramic

processes from an oxide (alumina) or non-oxide

(silicon carbide).

Advantages and Disadvantages of

Ceramics

Advantage:� High stiffness

� Hardness

� Hot hardness (remain hard even at high temperature)

� Compressive strength

� Relatively low density

Disadvantage:

� Low toughness and bulk

tensile strength

� Susceptibility to thermal

cracking

Ceramic Matrix Composites (CMC) represent an attempt to retain the desirable properties of ceramicswhile compensating for their weakness.

Ceramics are:

� High mechanical strength even at high temperature

� High thermal shock (abrupt temperature increase or decrease) resistance


� High toughness (crack resistance)

� High thermal stability


� High corrosion resistance even at high temperature


Properties


Properties

� Highmechanical strength


Properties

� High toughness (crack resistance) – fibers arrests (stops)

cracks from propagating (spreading).

fib

er

ma

trix

crack

crack

arrest

LOAD

Reinforcement

� Ceramic Matrix Composite is reinforced by either :

� Discontinuous (whiskers or short) fibers or Particles

� Continuous (long) fibers

� Discontinuous (Whiskers or Short Fibers) Fibers or Particles

� Ceramic Matrix is reinforced by whisker ceramic fibers like Silicon Carbide (SiC), Titanium Boride (TiB2), Aluminum Nitride(AlN), Zirconium Oxide (ZrO2) and other ceramic fibers or particles.

� Most of CMC are reinforced by Silicon Carbide (SiC) fibers due to their high strength and stiffness (elastic modulus).

� Whiskers (short fibers) incorporated (combined) in Ceramic Matrix improve ceramic toughness to resist crack propagation(spread).

� Failure Characteristic of short-fiber reinforced ceramic matrix composite is catastrophic (complete failure).

Reinforcement

� Continuous (Long Fibers) Fibers

� CMC is reinforced either by long (continuous) monofilament(single fiber) or multifilament (fiber bundle or strand) fibers.

� Reinforcing fibers are Silicon Carbide (SiC), Titanium Boride(TiB2), Aluminum Nitride (AlN), Zirconium Oxide (ZrO2) and other ceramic fibers.

� Best strengthening effect is obtained by continuous

monofilament fibers (Silicon Carbide [SiC] fibers).

� Monofilament fibers produce stronger interfacial bonding with

ceramic matrix � improve ceramic toughness.

� Failure Characteristic of long-fiber reinforced ceramic matrix

composites is not catastrophic (do not fail completely).

Matrix� Matrix material for Discontinuous (Whiskers or Short Fibers

or Particles) reinforcement are:

� Alumina (Alumina [Al2O3] -Silica [SiO2] or Mullite[3AL2O3*2SiO2] )

� Boron carbide (B4C)

� Boron nitride (BN)

� Silicon carbide (SiC)

� Silicon nitride (Si3N4)

� Titanium carbide (TiC)

� Matrix material for Continuous (Long Fibers) reinforcementare:

� Silicon carbide (SiC)

� Silicon nitride (Si3N4)

� Alumina (Alumina [Al2O3] -Silica [SiO2] ) or Mullite(3AL2O3*2SiO2)

Types of Ceramic Matrix Composite

and Applications

� Alumina Matrix Composite � matrix is Alumina or

Aluminum Oxide (Alumina [Al2O3] - Silica [SiO2] ) or Mullite

(3AL2O3*2SiO2).

� Fabricated by Sol-Gel or Direct Metal Oxidation (DEMOX) method.

� Use for:

� Manufacturing heat exchangers

� Filters for hot liquids

� Thermo-photovoltaic burners

� Burner stabilizers

� Combustion liners of gas turbine engines

Types of Ceramic Matrix Composite

and Applications

� Silicon Carbide (SiC) Matrix composite � matrix is silicon carbide (SiC).

� Fabricated by Chemical Vapor Infiltration (deposition) or Liquid Phase Infiltration method.

� Use for:

� Manufacturing combustion liners of gas turbine engines

� Hot gas re-circulating fans

� Heat exchangers

� Rocket propulsion components

� Filters for hot liquids

� Gas-fired burner parts

� Furnace pipe hangers

� Immersion burner tubes.

Processing

� Difficulties in processing:

� Need to develop high temperature reinforcement.

� Due to elevated temperature during hot pressing or sintering.

� Induced residual stress due to the differences in thermal expansion coefficients (CTE or α) of reinforcement and matrix.

� Whiskers or Short Fibers or Particles (discontinuous) reinforcement

⇒∝<∝

⇒∝>∝

matrixin crack radial

matrixin crack ntialcircumfere

MR

MR

R = reinforcement (fiber) M = matrix

αααα = thermal expansion coefficient (CTE)

Processing

� Difficulties in processing:

� Long Fiber (Continuous) reinforcement

⇒

⇒∝<∝

⇒

⇒∝>∝

crackingmatrix

matrixin stress ecompressiv residual

debonding interface

matrixin stress tensileresidual

MR

MR

R = reinforcement (fiber) M = matrix

αααα = thermal expansion coefficient (CTE)

Processing

� For CMC with Discontinuous Reinforcement (Whiskers or Short Fibers or Particles)� Manufactured by mixing the powdered matrix with the

reinforcing phase followed by pressing (compaction) at elevated temperature � hot pressing or Sintering Method(bond by partly fusing).

� For CMC with Continuous Reinforcement (Long Fibers)� Manufactured by Infiltration Method (Process) � ceramic

matrix is formed from a fluid (gaseous or liquid) which infiltrate(pass through) into the fiber structure or preform (either woven or non-woven or continuous fiber).

� Prior to the Infiltration Method � reinforcing fibers surface is coated with a debonding interphase.� Debonding Interphase � provide weak bonding between fiber

and matrix so that fiber slides in matrix (during infiltration process)and prevents brittle fracture of fiber.

Processing – Infiltration Methods

� For CMC with Continuous Reinforcement (Long Fibers)

� Not fabricated by sintering method due to:

� Mechanical damage of fibers during pressing.

� Chemical reaction between fiber and matrix (cause degradation)

during high temperature.

� High porosity (during compaction).

� Infiltration Methods (Processes)

� Slurry Infiltration

� Sol-Gel

� Chemical Vapor Infiltration (deposition)

� Direct Metal Oxidation (DIMOX)


� Slurry Infiltration � liquid phase infiltration method.

� Utilizes a slurry percolating (passing through) into a porousreinforcing preform (woven / textile or non-woven or continuous fibers).

� Infiltration process is by the capillary forces (capillary action)and once completed, the preform is dried and hot pressedforming a ceramic matrix composite.

� Slurry � ceramic particles dispersion (scattered) in a liquid carrier together with binders (for fiber-matrix interfacial bonding) and wetting agents (help capillary action).

� Produces denser structure with smaller shrinkage during processing due to higher content of solids (ceramic particles).

� Pressure or Vacuum assisted slurry Infiltration allows furtherincrease of the density of the resulting ceramic composite.


� Slurry Infiltration Process (SIP)

� SLURRY INFILTRATION. Reinforcing fibers (tow, tape, woven, non-woven or continuous) passes through a slurry (contains particles of the ceramic matrix) which penetrates into the porous structure of the reinforcing phase (fibers). Infiltration is by capillary effect (can be enhanced by vacuum or pressure).

� LAY-UP. Prepreg (infiltrated or impregnated fibers) is woundonto a mandrel. Then it is dried, cut and laid-up (stack) to a desired shape (fiber orientation) on a tooling (mold).

� HOT PRESSING. Hot pressing (sintering and densification) in Graphite die at high temperature and increased pressurewhich enhance the diffusion (compaction / consolidation for low porosity / voids resulting to high density) of the ceramic matrix between the fiber structure (woven or non-woven or continuous).


� Slurry

Infiltration Process (SIP)


� Ceramic Matrix Composite (CMC) produced in Slurry

Infiltration:

� Glass reinforced Ceramic

� Mullite (3AL2O3*2SiO2) Ceramic

� Silicon Carbide (SiC) Ceramic

� Silicon Nitride (Si3N4) Ceramic


� Sol-Gel � liquid matrix in colloidal (particulate) suspension of fine ceramic particles (sol) soaks (wet) a

preform (woven / textile or non-woven or continuous fibers) and then transforms to solid (gel).

� Colloidal suspension � contain very small (nano)particles (100 nm radius) within a liquid (water or organic solvent).

� Intrinsic (basic) part shapes can be produced by Sol-Gel Method.


� Sol-Gel Process

� Liquid sol (low viscosity) easily penetrates into a preform(woven or textile / non-woven or continuous fibers).

� Infiltrated preform is then dried.

� Drying operation causes matrix shrinkage and pores (voids)

formation therefore infiltration-drying cycle is repeated

several times until desired density is achieved.

� The resulting material is fired (exposed to fire or heat) and hot pressed.


� Chemical Vapor Infiltration (CVI) � widely used for fabrication of silicon carbide matrix composites reinforcedby long (continuous) silicon carbide fibers.

� Reacting gases, at isothermal (constant temperature)condition, is carried by a carrier gas (H2, Ar, He) stream and diffuse (spread naturally or by pressure) into a porous preform(woven or textile / non-woven or long fibers) and deposits a material (matrix) on fiber surface.

� Example � Silicon carbide (SiC) matrix is formed from a mixture of Methyltrichlorosilane (MTS or CH3Cl3Si) and Hydrogen as the carrier gas according to the reaction:

CH3Cl3Si �� SiC + 3HCl� Gaseous Hydrogen Chloride (HCl) is removed from preform

(fiber) by the diffusion or forced out by carrier stream.


� Chemical Vapor Infiltration (CVI)

� Deposited material(matrix)

� Result of chemical

reaction.

� Fills the spaces

between the fibers

and form composite

material (matrix �

deposited material,

fibers or preform

[reinforcement] �

dispersed phase).


� Chemical Vapor Infiltration (CVI)� Advantages:

� Low fiber damage (low infiltration temperature).� Matrix of high purity is produced.� Low infiltration temperatures = Low residual mechanical

stresses.� Enhanced mechanical properties (strength, elongation,

toughness).� Good thermal shock (sudden temperature change)

resistance.� Increased creep and oxidation resistance.� Matrices of various (different) compositions can be

fabricated (SiC, C, Si3N4, BN, B4C, ZrC, etc.).� Interphases (fiber-matrix coupling agent) may be deposited

in-situ (immediately right on) the fiber surface.


� Chemical Vapor Infiltration (CVI)

� Disadvantages:

� Slow process rate (may continue up to several weeks).

� High residual porosity (void) � 10%-15%.

� High capital and production costs.


� Direct metal oxidation (DIMOX) � matrix forms throughthe reaction of a molten metal with an oxidizing gas.

� 2 Conditions are necessary for the dispersed phase(reinforcement � fibers):

� Wetted by the melt (molten metal).

� Does not oxidize (do not react chemically) with the presence of

oxygen.

� Process rate � 1 mm/hr. – 1.5 mm/hr. (slow)

� Resulting CMC have no pores or voids / empty spaces(present in ceramics fabricated by sintering) and impurities(due to � binders, plasticizers, lubricants, deflocculants, water etc.).

� Use for fabrication of CMC with Alumina or Aluminum Oxide(Al2O3) matrix.

� Direct metal oxidation (DIMOX)

� Oxide growth (oxidized metal which forms ceramic matrix) may continue even after the reaction (oxidation) front has reached the outer surface of the preform so that the aluminum oxide will be deposited over the preform changing its dimensions.

� To prevent � preform surface is coated with a gas permeable

barrier so that the ceramic matrix growth stops when the reaction

front reaches the barrier.

� Residual Metal � non-reacted metal (5-15% of total aluminum volume used) is removed from the part surface.

� Some residual metal remains embedded in the inter-granular

spaces of the ceramic matrix (oxidized metal).


Processing – Infiltration Methods� Direct metal oxidation (DIMOX) process

� For fabrication of CMC with Alumina or Aluminum Oxide(Al2O3) matrix.

� Lay-up. The preform (SiC or Al2O3 reinforcing fiber, woven or

non-woven or continuous fiber) is laid and shaped according to

desired form.

� Application of Interphases. Thin layer (0.1 µm - 1 µm) of

debonding phase (Pyrolytic [carbon obtained after heating a

material] Carbon [C] or Hexagonal Boron Nitride [BN] ) is

deposited on the fiber surface by Chemical Vapor Infiltration

(CVI) method.

� Deposition (coating) of a Gas Permeable (allow to pass through)

Barrier on the preform surface.

� The surface through which the melt (molten metal) should wick

(capillary action) into the preform is not coated.



� Metal Oxidation.

� Preform is put in contact with liquid aluminum alloy (molten at 900OC - 1150OC).

Aluminum alloy is

doped (added) with

additives (magnesium,

silicon) to improve its

wettability (capillary

effect) on the reinforcing

fiber and enhance its

oxidation with oxygen.


� For fabrication of CMC with Alumina or Aluminum Oxide (Al2O3) matrix.


� Molten aluminum wicks (capillary action) into the reinforcing

structure (preform or fibers) through the non-coated surface (no

gas permeable coating).

� Oxygen penetrates into the preform (fibers) in the opposite direction passing through the gas permeable barrier (coating).




� Liquid aluminum and oxygen meet at the reaction (oxidation) front.

� Liquid aluminum oxidizes (becomes Al2O3 � ceramic matrix) as

it comes in contact with oxygen.




� A growing layer of oxidized aluminum forms and becomes the ceramic matrix.

� The process terminates (stops) when the reaction front reaches

the barrier (Gas Permeable barrier or coating).


� Direct metal oxidation (DIMOX)

� Advantages:

� Low shrinkage (near-net shape parts can be fabricated).

� Inexpensive and simple equipment.

� Inexpensive raw materials.

� Good mechanical properties at high temperature (creep strength) due to the absence of impurities.

� Low residual porosity.

� Disadvantages:

� Low productivity (ceramic matrix growth rate [oxidized molten metal] � 1 mm/hr. – 1.5 mm/hr).

� Too long fabrication time � 2-3 days.

� Residual (non-reacted) aluminum may be present in the oxide matrix.

Carbon-Carbon Composites

(CC)



Cum Fructo



Cum Laude



� Carbon-carbon composite (CC) – compose of a carbon (graphite form or crystalline) matrix reinforced by carbon (graphite form or crystalline) fibers (carbon atoms are well aligned).

Carbon (graphite form) Fibers


� Carbon-carbon composite (CC)

� Carbon matrix � from phenolic resins that have been repeatedly charred (burned or carbonized) and impregnated(soak) with phenolic resin.

� Very long process (up to 6 months for one part or product).

� Very costly.

� For very high temperature environment (up to 3,000OC).

� Very strong and light weight.

� FACT: First developed in 1958, but not intensively researcheduntil the Space Shuttle Program (for insulation).

Advantages and Disadvantages

� Advantages:

� Carbon fibers stops crack propagation (spread) of brittle carbon matrix � increasetoughness of carbon matrix (gradual failure).

� Extremely high thermal stability (up to 3,000OC).

� Needs flammability coating (ceramic to prevent burning and oxidation) at very high temperatures.

� Very strong and light weight (low density).

fib

er

ma

trix

crack

crack

arrest

LOAD

Advantages and Disadvantages� Advantages:

� Low creep (deform from stress or heat) at high temperature.

� Good tensile and compressive strengths.

� High fatigue (cyclic loading) resistance.

� High thermal conductivity (101 W/m-K).

� High friction coefficient.

� Disadvantages:

� Expensive (high production cost).

� Very long process (up to 6 months for one part or product).

� Low shear strength.

� Susceptibility to oxidation (easily oxidizes above 482OC) at high temperature.

� Need ceramic coating to prevent burning and oxidation

(increase cost of carbon-carbon composite).

Properties

� Outstanding durability at temperatures over 2000ºC (even as far as 3,000OC).

� Retain mechanical properties even at high temperature.

� Excellent heat resistance in non-oxidizing (no presence of oxygen) environment.

� Low thermal expansion coefficient (CTE).

� Great thermal shock resistance (abrupt / rapid temperature change).

� High melting point (3,600OC).

� Corrosion resistant.

� High electrical conductivity.

� High abrasion resistance.

� Low density (1,830 kg/m3).

� High strength and elastic modulus (up to 200 GPa).

Properties

� RetainMechanical

Properties

even at high temperature.

Properties

� OutstandingSpecific

Strength

(strength-to-weight ratio)

compared to

other metals.

Properties

� Mechanical Properties of Carbon-Carbon Composite

Processing� Low-Pressure Carbonization � pyrolysis and

graphitization at low pressure.

� Pyrolysis � chemical decomposition by heating (982OC-1,204OC for Chemical Vapor Infiltration and 538OC-1,000OC for Liquid Phase Infiltration) in the absence of oxygen to produceamorphous (non-crystalline) carbon.

� Graphitization � heating at higher temperature (2,500OC) to convert amorphous carbon into crystalline carbon.

Processing� Low-Pressure Carbonization Process

� Carbon fibers (preform or woven or non-woven / continuous) are laid-up and stacked according to desired pattern and structure.

� Patterns of woven fibers (fibers are in bundle / strand):

Processing

� Low-Pressure Carbonization Process

� Carbon fibers (preform or woven or non-woven / continuous) are laid-up and stacked according to desired pattern and structure.

� Patterns of woven fibers:


� Carbon fibers (preform or woven or non-woven / continuous) are impregnated with resin (phenolic, pitch, or furfuryl ester).

� Impregnated Resin serves as the carbon matrix after pyrolysis

and graphitization.

� Resin impregnation is by:

� Chemical Vapor Infiltration [deposition] (CVI or CVD) � preform

(woven or non-woven fibers) is infiltrated with a pressurized

hydrocarbon gas (propane, methane, propylene, acetylene,

benzene).

� Liquid Phase (resin bath) Infiltration � preform (woven or non-

woven fibers) is infiltrated with a liquid resin (petroleum pitch /

phenolic resin / coal tar).

Processing

� Low-Pressure Carbonization Process

� Impregnated resin is cured (thermosetting).

� Prolysis (982OC-1,204OC for Chemical Vapor Infiltration and538OC-1,000OC for liquid phase infiltration) of resin is done to produce carbon (amorphous / non-crystalline) matrix.

� Impregnation-pyrolysis is repeated 3-4 times to reduce porosityto acceptable level.

� Graphitization (at 2,500OC) to covert amorphous carbonmatrix into crystalline carbon matrix.


� Coating the outer layer of carbon-carbon composite with silicon carbide to prevent oxidation at high temperature.

� Carbon-carbon composite can oxidizes as low as 450OC.

� Oxidation protection of Carbon-Carbon Composites

� Ceramic coatings (commonly multi-layer) of carbides, nitridesand oxides can be deposited (coated) by Chemical Vapor Deposition or Infiltration (CVD or CVI).

� Oxidation inhibitors (stop or slow chemical reaction): inorganic salts, borate, silicate glasses, phosphates, boron oxides, polysiloxanes, halogen (inert or noble gases)compounds.

Applications

� Carbon-Carbon Composites are used for:

� High performance braking systems (for high speed aircarfts and vehilces).

� Brakes of aircraft, racing cars and trains.

Brake of Airbus A320

Brake Pads

Brake of F-1 Fighter Plane

Applications


� Bicycle frame.

Applications


� Refractory (heat resistant)components for hot-pressed dies, heating elements, turbojet engine components.

� Rocket nozzles and tips.

Thrust Chamber (Weaving /

3D-Axial Braiding at 1,800OC)Rocket Nozzel

Exhaust Tail-Cone (Weaving /

2D Cloth + Stitching at 1,300OC)

Applications


� Thermal protection of Space shuttle nose cones and leading edges upon re-entry.

Application Developments



Cum Fructo



Cum Laude


Reason For Composite Material Application

� Why do designers are thinking to use composites more and more?

� Function integration (combine) � reduce of number of parts(pieces).

� Weight reduction.

� Style freedom.

� Areas of Application

� Aerospace Industry

� Sporting Goods Industry

� Musical Instruments

� Shipbuilding Industry

� Automotive Industry

� Construction (Civil Engineering)

� Electrical and Electronics

� High Temperature operations

Areas of Application

� Composite Application Distribution

Estimated 1.8 Million

Tons of Composite

Shipment in year 2000.



� Lear Fan 2100 “all-composite” aircraft (Graphite-Epoxy Composite).



� Boeing 767, 777, and 787 airplanes with full wing box made of composite (Graphite-Epoxy Composite and Hybrid Graphite-Aramid-Epoxy Composite).

Areas of Application� Aerospace

Industry

� Composite body parts of an aircraft.



� Composite body parts of an aircraft.

Different partsof an airplanemade of composite

materials.

Areas of Application� Aerospace

Industry

� Compositebody parts of an aircraft.

Graphite Snowboard


� Sporting Goods

Industry

� Shoes.

� Snow Board.

� Bicycle Body Frame.

Composite Shoes

Composite Bicycle Body Frame


Composite(carbon fiber reinforced )Baseball Bat from Miken Sports

� Sporting Goods

Industry

� Baseball Bat

Laminated FiberglassBow


� Sporting Goods Industry

� Bow.

� Tennis Rackets.

Tennis Racket Handle made of Carbon Fiber Composite


� Musical Instruments

� Piccolo

� Banjo

� Guitar

Composite Piccolo

Composite Banjo

Composite Guitar


� Shipbiulding Industry

� Ship Hulls.

Swedish Navy

Stealth Ship (2005)

Yatch Hull

Dodge ViperComposite body parts

Front Grill of an Automobile



� Composite body parts of a car.



� Composite body parts of a car.

Skylight (sunroof)

Wipers Fuel System



� Composite Seat.

Seat Frame


� Construction (Civil Engineering)

� Bridge.

� Asbestos Cement Sheet for roofing material.

� Ferro-cement (cement with iron particles) for buildings and bridges.

Pedestrian Bridge

in Denmark, 130

feet long (1997)


� Electrical and Electronics

� Epoxy / Glass Fiber Composite

� Use in most modern circuit boards.

� For insulating PCB's and electronic assemblies.

� Melamine with Woven Glass Fibers Composite

� Insulator against electric arc.

� Mica / Glass Fiber Composite in Tapes and Sheets

� Useful up to 600OC.

� Insulator for corona (electrical discharge) and high voltage.

� Insulator for radiation and moisture.

� Silicone / Glass Fiber Composite

� Good dielectric (electrical insulator) when dry.

� Nylon / Woven Glass Fiber Composite

� Electrical insulator.

� High temperature insulator.


� High Temperature Operations

� Glass Fiber Composites

� Insulator for high temperature operations.

composite materials (1)

Documents