1. Plank #7 and beyond

2. 2 What was new for plank#7? Carbon-fibre jig Oversize (by 10mm) facesheets during stave core build –Facesheets now at the very limit of curved co-cure jig → will move to halfpipe (like LBNL) –No contamination of jig surface (as expected) –Facesheets are milled to size after stave core build – worked ok, but want to investigate more gentle methods First full-size core with 45gsm prepreg made in UK –Both facesheets developed crinkles during co-cure (CF & tape together) Is this because jig too small? Or because of UK tape? Glue applied to pipe instead of foam blocks –This brought the amount of glue used for this step from >20g to <4g –No glue between upper and lower foam blocks Thermally probably ok (as long as there is no other fault, but what’s the impact on shear rigidity?) Glue mixer

3. Pictures 3 Side A (bottom) Side B (top) Pipe glue applicator

4. 4 Weights Total weight of stave core: 308.64g (plank#6: 444.37g) Weight reduction per facesheet: ~50g –100gsm → 45gsm expect ~25g –Rest due to different tape build-up (Altaflex vs UK)? Glue has been reduced from 75g to 26g

5. 5 Flatness After removal of z-dependence

6. Stiffness Plank with similar build-up (45gsm K13C2U/EX1515) is US stave –Compared to that plank#7 has 20% higher bending stiffness (without taking sandwich thickness into account) –Shear rigidity was not measurable for US stave, for plank#7 lower than other planks we built, but not clear how biased by bending stiffness 6 PlankMaterialComment Weight plank [g] Weight glue [g] 180gsm K13D2U/RS-3Multiple delaminations420.053.5 (12.7%) 280gsm K13D2U/RS-3Thermo-mechanical444.191.6 (20.6%) 380gsm K13D2U/RS-3No tapes317.2 480gsm K13D2U/RS-3Foam core449.6 580gsm K13D2U/RS-3Corrugated core444.7 US45gsm K13C2U/EX1515Tube close-outs390.532.4 (8.3%) 6100gsm K13C2U/EX1515444.475.4 (17.0%) 745gsm K13C2U/EX1515308.626.4 (8.6%)

7. What should we do next? Thin stave: to get a feeling for integrity and stiffness of such a stave –2mm cooling pipe (material uncritical) –Need special close-outs –Special inserts for C-channel jig (but main part can be used without modification) And/or stave with multiple broken cooling pipe: To address concerns about internal weld joints –Cooling pipe diameter and material TBD (I naively assume the most critical would be larger diameter and Ti) –The rest of the stave would be as usual, but we could do another corrugated core (low mass) –This should then go into the QMUL thermal chamber And/or…? And what should we do with plank#7 (and plank#6)? 7