Tim 12cm Panel Assembly Cocuring development Feb 11 USmade TMS tapes cut into 50cm lengths Cocured on CF jig with K13D2URS3 pre preg Tape facing internal surface of curved CF tooling ID: 472195
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Slide1
Results from Thermal Cycling of a 12cm square co-cured sandwich
TimSlide2
12cm Panel Assembly
Co-curing development (Feb ‘11)
US-made TMS tapes cut into 50cm lengths
Co-cured on CF jig with K13D2U/RS3 pre-pregTape facing internal surface of curved CF tooling0/90/0 pre-preg layup125C cure for 4 hours at 5barVisually looked OK. No signs of de-lamination with handlingFollowing observations at QMULManufacture 12cm square test panelsCut face sheets into 12cm lengthsUCF126-3/8-2.0 honeycombAdvanced Composites Group VTA260 188gsm glue film cut to honeycomb patternGlued at 80C for 5 hours.Thermal CycleSeal in bag & put in -45C freezerExpecting to test whether honeycomb to face sheet interface failed!
08/05/2011
2
12cm Co-cured Sandwich TestsSlide3
Plate #1
Found to be de-laminated over ~ 80% of area when removed from freezer after 1 hour
Two parts separated
Tape-side: 2 layers of CFSandwich side: 1 layer of CFSandwichTape08/05/20113
12cm Co-cured Sandwich TestsSlide4
Further Tests
Manufactured 2
nd
PlateDe-lamination (~ 20%)Not yet separatedFace-sheet onlyDecided not to waste any more HC/glue!Cut 2 further 12cm lengths of tape/CF and cycled themBoth delaminated (from the corners) over about 30% of area Plate #2Plate #1
Sheet #1
Sheet #2
08/05/2011
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12cm Co-cured Sandwich TestsSlide5
Thoughts
About the pre-
preg
It’s old (beyond the 6month manufacturer’s shelf life)It’s cured at the very bottom end of the approved cure cyclesThe resin fraction is quite low (29%)About the tapesThese are US-made thermo-mechanical tapes which have thicker aluminium than the Oxford made tapes ?About Co-curingThese sheets were cured with tape down on the internal surface of the CF jig – I think I recall that this is the orientation which gave more problems at Oxford ?About the TestCould the sample geometry (square) increase stress concentrations at the corners?Could trapped moisture expand on freezing & promote de-lamination?08/05/2011512cm Co-cured Sandwich TestsSlide6
Future
Failure presumably due to stresses arising from differential CTE
RT difference (120 – 20) = 100
CCO2 difference (120 – (-40)) = 160 CNew Tencate pre-pregK13C2U/EX-1515Standard cure at 120 C32% RCPossible ACG Pre-pregK13C2U/LTM123Standard cure at 80 CMy ViewEVEN IF co-cured face sheets work with best quality RS3, EX-1515 or LTM123 resins we need to:-
Know what the margin of safety is for a specific combination of:-
Pre-preg (cure temp, modulus, resin CTE)Bus tape (
kapton
thickness, aluminium thickness & CTEs
Operating temperature
I
dentify someone who can simulate the operational and failure stresses
D
evelop a sample geometry and devise a test regime to impart stresses
08/05/2011
6
12cm Co-cured Sandwich Tests