Some Comments on the Use of CGL for the Foam-Pipe Interface 1 D. Lynn (BNL), LBNL Mechanical Meeting, Sep 2012 We have been using CGL exclusively in the US. Plan was for UK to use hysol for their staves and we would later compare. Now is a good time to compare. Concern with CGL was that it might leach into foam pores. We think we have solved that potential problem. We also irradiated CGL to ~ 1 x p+/cm 2 and found no change in consistency. Main motivation for use of CGL was to decouple forces generated by CTE mismatch of the facings and the pipe that might distort the stave or rupture the foam. It is not clear this decoupling occurs.

Possible solution to Allcomp “ragged edge” problem Create a 1-2 mm thick layer of Hysol on interface surface of foam and allow to cure; Machine with ball endmill as before; Apply coating of Hysol as before to seal pores on semi-cylindrical surface… Apply Hysol layerMachine foam as before Note improved edge From Sep 2011 LSWG Meeting at LBNL 2

Foam Sealed with Hysol; Sharper Machined Edges 3 The technique works, but involves step of sealing foam

Standard 1.3 m Stave (SS) Co-Cured (CC)1.2 m Stave Stave Contraction Tests on Two Staves with CGL on Foam-Pipe Interface No bus on SS. SS used ~ 80 gsm fiber CC used ~ 45 gsm fiber 4 Weights are in grams

5 Stave Contraction Result on 1.2 m Co-cured Stave

6 Stave Contraction Result on 1.3 m Standard Stave  x 2 = 840  m seems unlikely to be possible 2

7 Possible Way to Measure What is Occurring During DC-DC Stave Assembly

8  L = -25  m for 1.3 m standard stave is consistent with full decoupling of pipe from facing. However  x = 160  m is hard to explain if pipe really contracts ~ 1 mm. Maybe pipe doesn’t contract due to facing stiffness and foam shear stiffness? For 1.2 m co-cured stave, get  L = 200  m. Is this due to coupling between pipe and facing, or due to coupling of bus cable and facing? Note that the facings use 45 gsm also and are thus less stiff Can we measure the CTE of just a co-cured facing (or simulate)? Is it possible to get similar measurements with UK staves that use hysol? Final Comments and Observations Rough calculation of facing contraction (only carbon fiber and aluminum) t c = 150  m = thickness of 3 plies of 45 gsm carbon fiber (160  m was measured), Effective modulus was calculated to be ~ 250 Gpa. t a = 50  m = thickness aluminum shield, modulus of 70 GPa Carbon fiber does not contract, aluminum wants to contract about 1400  m when cooled 50 degrees over 1.2 m  L 250 GPa t c = 70 GPa (1380  m –  L) t a to balance forces. Implies  L ~ 120  m If included copper this might take us closer to 200  m