Plank #7 and beyond

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

Pictures

3

Side A (bottom)

Side B (top)

Pipe glue applicator

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

Face sheet 1 (estimated)

Face sheet 2

Lower foam blocks (estimated)

Close outs

Upper foam blocks (incl bend)

cooling pipe (with plugs)

C-channels

honeycomb sections

Glue estimated

0

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Face

shee

ts

Foam

C-cha

nnel

s & cl

ose-

outs

Coolin

g pip

e

Honey

com

bGlu

e

we

igh

t [g

]

Stave #6

Stave #7

5

FlatnessPlank #7 Side A

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160

0 200 400 600 800 1000 1200

Plank #7 - side B

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180

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-0.2

-0.15

-0.1

-0.05

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0.05

0.1

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0.2

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position [mm]

dis

pla

cem

ent

[mm

]

side A

side B

-0.1

-0.05

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transverse position [mm]

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pla

cem

ent

sid

e A

[m

m]

-0.3

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-0.05

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0.1

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pla

cem

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sid

e B

[m

m]

Side A

Side B

After removal of z-dependence

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

16.13

29.41

24.66

12.85

64.03

33.10

10.79

102.63 102.83 101.4892.38 101.39

51.83

133.42

61.59

0

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120b

end

ing

sti

ffn

ess

[Nm

2 ]

shea

r ri

gid

ity

[kN

]

beam shear rigidity

beam bending stiffness

Plank Material CommentWeight

plank [g]Weightglue [g]

1 80gsm K13D2U/RS-3 Multiple delaminations 420.0 53.5 (12.7%)

2 80gsm K13D2U/RS-3 Thermo-mechanical 444.1 91.6 (20.6%)

3 80gsm K13D2U/RS-3 No tapes 317.2

4 80gsm K13D2U/RS-3 Foam core 449.6

5 80gsm K13D2U/RS-3 Corrugated core 444.7

US 45gsm K13C2U/EX1515 Tube close-outs 390.5 32.4 (8.3%)

6 100gsm K13C2U/EX1515 444.4 75.4 (17.0%)

7 45gsm K13C2U/EX1515 308.6 26.4 (8.6%)

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