MIT Rocket TeamNovember 20, 2010

Design and Fabrication

An Introduction to COMPOSITES

Carbon Fiber Carbon fiber custom laminate Material: 5.7 oz 3k twill carbon fiber

sheet Epoxy

Aeropoxy 2032 resin Aeropoxy 3665 hardener

Aspects High strength-to-

weight ratio High cost

Fiberglass

Carbon fiber is RF opaque Material: 6 oz plain weave fiberglass Epoxy

Aeropoxy 2032 resin Aeropoxy 3665 hardener

Locations Fairing Potentially second

stage body or sections

General Fabrication Techniques Elevated temperature cure

Custom-built oven Inner dimensions sufficient for full

cure of either stage Capable of reaching in excess of

300º F Not necessary for epoxy choice, but

provides additional temperature resistance

Reduces cure time Improves resin distribution and

mechanical properties

Vacuum bagging Improves surface

finish of part Reduces weight

before removal of excess epoxy

Body Tube Ply Layup Determine number of plies

Meet loading requirements Manufacturing reasons

Additional plies at bulkheads and ends Antisymmetic and Axisymmetric

Your Mission

Fin Design Sandwich laminate

Balsa core (1/8”) Single–layer carbon fiber facesheets

Construction Cut balsa to shape Cut vacuum bagging materials Apply thin film of epoxy to balsa Apply facesheets Apply additional epoxy and ensure is well

distributed Apply vacuum bag release, then breather, then

strechlon Insert vacuum tube and cover edges with sealant

tape Fin Sizing

Semispan: 5” Chord: 5”-3”

[Build Composites]

Rocket BasicsAn Introduction to ROCKETS

Rocket Equation

Initial Mass Propellant Structural Mass Fraction Payload

Delta-V to Earth orbit: ~10 km/s

Propulsion Type Isp

Solid 250

LO2+LH2 450

LO2+RP-1 350

Electric 2000

Composites Design

What are composites?

Single Ply Carbon or glass fibers Epoxy matrix Usually unidirectional, but can be weave

Laminate Multiple plies

Sandwich Face sheets of plies Spacer material between

Why Composites?

Evaluation of Composites

Standard Laminates Rule of Mixtures E T c = v fE T f + v mE T m

Stiffness is simply the average of stiffnesses Be sure to account for direction

Z

T

Lgraphite/epoxy

Matrix

Fiber

Z

T

L

Sandwich Materials

Composites Fabrication

Techniques (Cont)

Body Tube Manufacturing

Prepare mandrel of phenolic tube with wax, mylar

Apply resin Apply fabric and work in resin Repeat for all plies Remove excess Apply vacuum bag material Bake for 1 hour Remove from mandrel Cut then sand edges

Bulkhead Design

Purpose: attach motor casings to airframe Design Options

Plastic rings Holes included around periphery for wiring and

antenna Inner portion secured with tape friction fit Outer portion secured with epoxy from both sides

COTS casings

Validation Static pull motor simulation Static fire testing

Fairing Design Material: Fiberglass Design Options

Tangent ogive: easy to build Von Karman: drag for large mach range Parabola: drag at subsonic speeds

Construction Layup in halves on aluminum mandrel and

plate Cure halves Affix together with strips Cure again Sand until smooth Apply additional filler as necessary

Composites Fabrication Examples

Fins

Body Tube

Nose Cone

Completed

SpaceX Interstage Mandrel

Composite Testing

Instron Testing

Prep

Load Testing

Engine Testing

Pyro Test

On the Launch Rail

Launch

Merlin Engine

Engine Fires

Static Fires

Questions?