Raw Material & Sub-Assembly QA (Tim) 25/09/14 25/09/2014Material & Sub-assembly QA1

Scope Stave Core Assembly needs raw materials and sub-assemblies Raw Materials (things that come as a ‘batch’, things which originate in industry?) – CFRP pre-preg - roll of 11” width – Hysol EA9396 – 1USQ packs – Boron-nitride powder – End closeouts – ‘C’-channels – Positioners & locking points – Bus Tapes – Honeycomb – Thermally-conducting foam Assemblies – Cooling loops – Co-cured face-sheets? 25/09/2014Material & Sub-assembly QA2

Schematic 25/09/2014Material & Sub-assembly QA3

During Pre-production Need to understand how potential defects in raw materials might translate into a measurable change in final stave core performance. Eg: – 10% decrease in thermal conductivity of foam – Gaps & wiggles in the 45gsm pre-preg – 10% lower honeycomb shear modulus – Effect of variation in 100:30 Hysol glue mix (95:35 to 105:25 say) – Effect of ‘C’-channel twist on final stave core geometry We have to rely on FEA for this as it is impractical to procure small batches of raw material with such property variations – Need to make sure the FEAs are up-to-date and validated by performance comparisons with ‘perfect’ objects Then we can place meaningful tolerances on critical parameters. Eg; – ‘C’-channel twist: torque needed to make a twisted ‘C’-channel flat is < some limit – Need to mix Hysol to (100+/-2:30-/+2) and therefore need measuring systems accurate enough to guarantee the +/-2 – Reject sections of pre-preg where there is a gap of more than 3mm over a length of more than 30mm Then we can develop easy-to-use test systems which can measure critical parameters to better than (say) 1/3 of the permitted tolerance. – i.e. we shouldn’t set specification which are so tight making the measurements becomes too onerous – conversely the test systems must have sufficient resolution to avoid rejecting perfectly good items through random error. 25/09/2014Material & Sub-assembly QA4

During Production Apply the test systems developed consistently and in a timely manner – Very important that we give rapid feed-back to the suppliers of any changes in quality A batch comes in and we need to check it out immediately Therefore may need multiple test systems to come with the spike & some fraction of the effort is naturally ‘pulsed’ – Very tight link with procurement, stock control & payment Especially important for long lead-time & single-source supplies (eg. Allcomp foam, CF honeycomb, pre-preg) 25/09/2014Material & Sub-assembly QA5

Sub-Assemblies Here I considered two; cooling loop & co-cured face sheets – Each is a composite item made from several components, each of which would have its own parts flow & quality control systems From a Stave Core Assembly point of view they’re just a ‘raw material’ except that ‘we’ manufacture them – We can ensure that the proper QC happens during sub- assembly manufacture However….. We may (be asked/choose to) manufacture more of these than the UK share in return for some other in-kind contribution – We will therefore carry a much greater burden of scrutiny as a quality control failure here will propagate to the whole barrel strip stave assembly project 25/09/2014Material & Sub-assembly QA6

So… what to test? ItemTests K13C2U/EX-1515 pre-pregWaviness, gaps, laminate density, CPT, areal weight, degree of cure (DSC), FTIR Tensile modulus (0/90), tensile strength (0/90), thermal conductivity K9 FoamDensity, Thermal Conductivity, compressive modulus, shear modulus… HoneycombDensity, shear modulus, cell uniformity… Hysol EA9396Tensile strength at nominal & slightly wrong mixes. Degree of cure after 3days at RT (DSC)… ‘C’-channelsChannel geometry, mass, straightness, resistance to flattening if twisted… 25/09/2014Material & Sub-assembly QA7

Comments The list becomes quite long! – But we shouldn’t worry – it’s good to start with a long list and then go though each item and take a critical view of each test to see if we think it’s sensible – For those tests which we would like to keep we nee to ensure that the required facilities exist and would be accessible to us during production – remember we really do need rapid feedback so we can’t have ‘I might be able to do it next week sometime!’ Ideally we want the minimum number of tests during production to guarantee quality plus a couple more just in case! – Likely that equipment cannot exist in one place (might even not be preferable) Should compile a list of facilities (together with access constraints) which can be used in both the pre-production and production phases. My inclination is that during production we don’t necessarily need to have access to state-of-the-art equipment but need something which is capable of resolving variations which we might be sensitive to. 25/09/2014Material & Sub-assembly QA8

Next Steps 25/09/2014Material & Sub-assembly QA9