Out-of-Autoclave Prepreg Introduction - Centre of Structure ...

Out-of-Autoclave Prepreg Introduction
Advanced Composites Processing
Bryan Louis

Outline
• Introduction (OOA prepreg)
• Examples
• History
• Modern OOA prepreg development
• Summary
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Out-of-Autoclave Prepregs
• Prepregs designed specifically for processing without the autoclave
• Potential processing cost reduction
• Autoclaves are expensive equipment capital
• Less expensive tooling material (OOA typically low-moderate cure
temperature)
• *Energy savings
• Larger manufacturer and subcontractor base
• No size limitations imposed by the autoclave
• Large interest in aerospace sector
• Including primary structures
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Out-of-Autoclave Prepreg Applications
• Major application sectors of OOA prepreg:
• Marine
• Infrastructure
• Wind energy
• Tidal energy
• Prototyping in aerospace
• Airplane structures
• Tooling
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Out-of-Autoclave Prepregs
vs
• Resin system designed for oven cure
• Vacuum-bag-only processing
• Target: laminate properties comparable to autoclave processing
Traditional OOA prepregs have a HIGH final void content
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Key differences from autoclave prepreg
• Autoclave prepreg (AC)
• Typical cure temperatures 180C
• Laminate quality (void reduction) achieved by hydrostatic pressure forcing entrapped
air and volatiles into solution
• Out-of-autoclave prepreg (OOA)
• Low cost oven/vacuum bag process
• Laminate quality (void reduction) achieved by extracting entrapped gases and
volatiles prior to gelation
• “breathable” prepregs
• Viscosity during cure cycle (Rheology) critical – remain “breathable” for sufficient time
• AC prepregs cannot simply be cured out of autoclave
• High voidage!
• Resin rheology is not tuned for dependence on vacuum extraction of entrapped gases
and volatiles
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Examples
• Spaceship 2 and White
Knight 2 (Virgin Galactic)
• Scaled Composites
(California, USA)
• OOA Material: Advanced
Composites Group
MTM45-1 (Umeco)
Source: http://www.virgingalactic.com/multimedia/album/graphics-and-illustrations/
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Examples
• Bombardier Learjet 85
• Bombardier Aerospace
• Fuselage and wings
• OOA Material: Cytec
5320
Source: http://www.learjet85.com/en/multimedia.html#a64-74
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History
• Original OOA systems not for structural applications
• Low mechanical properties
• Developed for prototyping
• Oven cure only
• Low temperature cure (cheap tooling)
• Early attempts for processing autoclave prepreg oven-only
was unsuccessful
• Years for prepreg manufacturers to understand OOA
material requirements
• Void removal without high applied pressure
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Source: SAMPE Seattle OOA tutorial. Chris Ridgard, 2010
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Source: SAMPE Seattle tutorial. Chris Ridgard, 2010
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Modern OOA Prepreg development
• Newer OOA prepreg systems has been aided by a better
understanding of mechanisms of air extraction
• Tailoring resin rheology
• Modern OOA prepreg systems developed early 2000’s
• Quality similar to autoclave processed prepreg systems
• Void free
• Similar mechanical performance
Source: SAMPE Seattle OOA
tutorial. Chris Ridgard, 2010
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Modern OOA Prepreg development
• Low void content is achieved by “breathing” out of
entrapped gases and volatiles
• Partial impregnations
• Resin rheology
• Air pathways can be created by partially impregnating
prepreg
• Initial dry regions (prior to cure) are wetted out during resin cure
cycle
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Boeing demonstrator launch fairing
• Constructed of Cytec 5320 prepreg
Sectioned Boeing fairing
Cross-section cut of laminate
Source: Composites World. www.compositesworld.com
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America’s cup racing boat
• Team Alinghi 2003 America’s cup challenger
Source: Advanced Composites Group
• Advanced Composite Group VTM 264 Unidirectional
Carbon/epoxy
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Tooling
Tool of a Volvo 70 sailboat (two days to laminate)
Source: SAMPE Seattle tutorial. Chris Ridgard, 2010
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Source: SAMPE Baltimore OOA tutorial. Chris Ridgard, 2012
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Source: SAMPE Baltimore OOA tutorial. Chris Ridgard, 2012
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Source: SAMPE Seattle OOA tutorial. Chris Ridgard, 2010
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OOA Prepreg Summary
• OOA prepreg can give laminates with similar quality to
autoclave processed
• Potential alternative to autoclave processed prepreg
• Proper processing is key to OOA prepreg laminate quality
• Gas extraction is key for OOA processing
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