ROCKETS AND COMPOSITES
Design and Fabrication
MIT Rocket Team
November 20, 2010
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
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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
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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]
Basics to
An Rocket
Introduction
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
 ETc = v f ETf + v m ETm
 Stiffness is simply the average of stiffnesses
 Be sure to account for direction
Z
Z
Matrix
Fiber
T
T
L
L
graphite/epoxy
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
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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?