Fiber reinforced plastic in sandwich

panels

ByK.NAGARAJU

121565

1. Introduction2. Fiber reinforced plastic3. Sandwich panels4. Sandwich panels jointing and connection

methods5. Applications of sandwich structures6. Advantages and disadvantages7. Reference

Contents

Fibre Reinforced Plastic or FRP is a composite material consisting of reinforcing fibres thermosetting resins and other materials such as fillers and pigments may also be present.

Glass fibre is generally used as a reinforcing material and polyester resins are usually used as bending agent.

Introduction

Fibre-reinforced plastic (FRP) (also fibre-reinforced polymer) is a composite material made of a polymer matrix reinforced with fibres.

The fibres are usually glass, carbon, or aramid, although other fibres such as paper or wood or asbestos have been sometimes used.

The polymer is usually an epoxy, vinylester or polyester thermosetting plastic, and phenol formaldehyde resins are still in use. FRPs are commonly used in the aerospace, automotive, marine, and construction industries.

Fiber reinforced plastic

FRP involves two distinct processes, the first is the process whereby the fibrous material is manufactured and formed, the second is the process whereby fibrous materials are bonded with the matrix during the moulding process.

Fiber reinforced plastics are made by combining fibers and resins called composites.

Combination of two or more materials Composite = matrix + fiber (filler):• Matrix:

• material component that surrounds the fiber.

• Usually a ductile, or tough, material w/ low density

• Strength usually = 1/10 (or less) than that of fiber

• Examples include: thermoplastic or thermoset• Thermoset most common (epoxy, pheneolic)

• Serves to hold the fiber (filler) in a favorable orientation

Fibers : Spin molten glass Different types of glass can be made

◦ E-glass (improved electrical resistance)◦ S-glass (high strength)◦ C-glass (high chemical resistance)

A sandwich-structured composite is a special class of composite materials that is fabricated by attaching two thin but stiff skins to a lightweight but thick core.

The core material is normally low strength material, but its higher thickness provides the sandwich composite with high bending stiffness with overall low density.

Sandwich panels

Metal composite material (MCM) is a type of sandwich formed from two thin skins of metal bonded to a plastic core in a continuous process under controlled pressure, heat, and tension.

Recycled paperis also now being used over a closed-cell recycled kraft honeycomb core, creating a lightweight, strong, and fully repulpable composite board. This material is being used for applications including point-of-purchase displays, bulkheads, recyclable office furniture, exhibition stands, and wall dividers

Types of sandwich structures

To fix different panels, among other solutions, a transition zone is normally used, which is a gradual reduction of the core height, until the two fiber skins are in touch. In this place, the fixation can be made by means of bolts, rivets, or adhesive.

The strength of the composite material is dependent largely on two factors:

The outer skins: If the sandwich is supported on both sides, and then stressed by means of a force in the middle of the beam, then the bending moment will introduce shear forces in the material. The shear forces result in the bottom skin in tension and the top skin in compression. The core material spaces these two skins apart. The thicker the core material the stronger the composite. This principle works in much the same way as an I-beam does.

The interface between the core and the skin: Because the shear stresses in the composite material change rapidly between the core and the skin, the adhesive layer also sees some degree of shear force. If the adhesive bond between the two layers is too weak, the most probable result will be delamination.

Properties of sandwich structures

Sandwiched panel with honeycomb core

Sandwich panel jointing and connection methods

Sandwich structures can be widely used in sandwich panels, this kinds of panels can be in different types such as FRP sandwich panel, aluminum composite panel etc.

FRP polyester reinforced composite honeycomb panel(sandwich panel) is made of polyester reinforced plastic, multi-axial high-strength glass fiber and PP honeycomb panel in special antiskid tread pattern mold through the process of constant temperature vacuum adsorption & agglutination and solidification.

Applications of sandwich structures

Advantages:◦ High strength to weight ratio (low density high tensile

strength) or high specific strength ratio! 1020 HRS spec strength = 1 (E6 in) Graphite/Epoxy, spec strength = 5 (E6 in)

◦ High creep resistance◦ High tensile strength at elevated temperatures◦ High toughness◦ Generally perform better than steel or aluminum in

applications where cyclic loads are encountered leading to potential fatigue failure (i.e. helicopter blades).

◦ Impact loads or vibration – composites can be specially formulated with high toughness and high damping to reduce these load inputs.

◦ Some composites can have much higher wear resistance than metals.

◦ Corrosion resistance◦ Dimensional changes due to temp changes can be much less.◦ Anisotropic – bi-directional properties can be design

advantage (i.e. helicopter blades)

Advantages

Disadvantages (or limitations):◦ Material costs◦ Fabrication/ manufacturing difficulties◦ Repair can be difficult◦ Wider range of variability (statistical spread)◦ Operating temperature can be an issue for

polymeric matrix (i.e. 500 F). Less an issue for metal matrix (2,700 F).

◦ Properties non-isotropic makes design difficult!

Example – video test in line w/ fibers 10X stronger vs fibers oriented at an angle.

◦ Inspection and testing typically more complex.

Disadvantages

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