Mechanics R&D Ian Wilmut

Talk Scope This talk is to provoke conversation – not to direct activities. The slides should do no more than start the conversation. We have 60 minutes to cover the following R&D activities, and how we should take them forward: – Mechanical prototyping of staves – Support structures – Stave to structure Mechanical interfaces – Stave insertion – Material optimisation

Why have this discussion now? The baseline stave design is fairly mature – but the collaboration still knows remarkably little about what sits around the stave. Thus we don’t have a complete solution – what we need to do is complete the solution to make sure that we are making the right stave to get the lowest material, and an appropriate system. In real terms these questions need to be answered in the next 18 months as beyond that point a significant rework of the system is increasingly unlikely.

Stave prototyping We have a set of open questions on staves – we need to answer these first for the 250nm stave and then the 130nm stave. – What should the core be? – Are the C channels right? – How do we handle the Z=0 end – should there be a bar? Should there be U shaped foam? – How to smooth the surface of the co-cure? – Can we keep the plank flat through the build? I believe the questions above are independent of things outside our control. Have I missed any?

Structures The UK has no intent to design the final structures – but no one else is progressing it at the moment. What we need to address, is how we can understand the structure-stave material balance with the least possible effort. We should remember as we look at this problem that we are not trying to produce a final design of the cylinders – we are only trying to develop an understanding of the optimal design. Question: How will we establish how the stave and structure should share material and stiffness? Question: How and who will do this?

Stave to structure interfaces Stephanie has a locking point demonstrator that I feel is very convincing. Feeling is that we should prototype at least 3 staves with this system to trial run the whole system. Whilst that prototype is happening there are further developments we need: – How to mass produce these items? For PEEK and LCP E~10-15Mpa and ρ~1.5g/cc where aluminium E~70Mpa and ρ~2.7g/cc so Aluminium has a higher stiffness/X0 ratio. – When we have a chosen material what about creep? – Can we keep the staves symmetric? – How do we integrate with interlinks/end of stave? – How much material can we drive out in next iteration?

Stave insertion Stave insertion is part of the stave transport frame and very closely linked with integration I believe most of the below is on-going but a general discussion will make sure everyone understands the process – How and when to add the end of stave interlink? – If we have two part locking points, how and when are they added? – What will a single stave frame weigh? Is this the right number? – What protections are there for the stave during insertion? and placing into the insertion tooling? – How will the stave be slid in, locked, and the tooling removed?

Material optimisation X0 is the driving force behind any final design. We should always be aiming to provide the most efficient design for a given X0. The previous 4 slides all have X0 implications. We need to take the work of all areas and try and understand how much material we are putting in for our convenience – and ensure that it is well distributed between the sub systems i.e. – Stave stiffness vs structure stiffness – Locking point material vs material saved in stave because of good coupling – Extra material penalty of making removable locking points – Are removable insertion rails really less material?

Just to provoke… MaterialE (Gpa)Ρ(g/cc)D0 E/E ss X0 compared with SS (D0 ss *(E/E ss ))/D) lower is better Stainless steel Aluminium CFRP (high modulus) CFRP cloth Torlon121.6~ PEEK LCP141.5~ So assuming there are no manufacturing constraints aluminium might be a better choice than PEEK or similar This all assumes structural stiffness is the primary design feature

Discussion We have 60 minutes to cover the following R&D activities, and how we should take them forward: – Mechanical prototyping of staves – Support structures – Stave to structure Mechanical interfaces – Stave insertion – Material optimisation