Stave core assembly Stephanie Yang WP4 face to face meeting, Lancaster University 20 Feb 2014

Outline Recent Stave building experience – Plank#9 –> for wire bonding trial ( to evaluate if C- channel close out is adequate ) – Stave building steps Stave tooling Observations

Main Steps (Tape + CF prepreg) to make a pair of co-cured face sheets Glue lower foam blocks Glue cooling pipe, upper foam blocks and end closeouts Glue CF c-channels (side closeouts) Glue honeycomb core CNC machine to the designated height Glue the top skin on Trim Stave to size (using vacuum jig and C channel clamping pieces).

Some pictures  Partial stave core assembly after CNC machined to the designated core height (4.6mm from the face sheet).  Honeycomb at various places have been ripped off –> not enough glue! Smaller honeycomb pieces shows better gluing result than the bigger / longer pieces -> possible explanation and it needs to investigate further.  The ripped off honeycomb area have been repaired with Hysol and abrasive paper is used to bring it to the same height as the rest. Ripped off HC after machining

Stave tooling Current stave tooling used: – CF Vacuum Jig – C channel clamping jig – Cooling pipe gluing jig – Rulers and various location blocks New stave tooling – This includes new vacuum jig; – Stave side close out placement jig; – Other new jigs / modification on existing jig design as required.

New Vacuum jig Various hole patterns need to be added on the vacuum jig for the stave tooling (e.g. holes for reference corner pieces, c channel clamp jig, etc….). In addition, it – Provides reference features for gluing the locking points. – Provides 2 off 10mm dia dowel through holes and 8 off M10 clearance through holes are needed for positioning and fixing the vacuum jig onto the sub-plate of the CNC machine at Oxford (steel inserts preferred, holes go through those Steel pads at the bottom side of the jig). See next slide for detail. – Max length of the jig has to be under 1.6m. 2 off 10mm dia Dowel hole thru 8 off M10 clearance hole thru

X-section view Vacuum jig that holds the stave core Sub-plate on CNC machine Steel bush built into the vacuum jig Steel pad

Stave side closeout placement jig C channel clamping jig new design allows the variable stave width. If the stave side closeouts is changed from CF C-channels into other shaped channels (e.g. box section), this design will have to change.

Observations The old procedure suggested that the lower foam blocks glued on the face sheet first, then machine the cooling pipe channels and also to height; but recently 2 or 3 staves were done by machining the lower foam blocks to size before gluing to the face sheet. Need to decide which way to go. The cooling pipe gluing jig worked well, but need to improve (e.g. current jig can’t go through U-bend, also is difficult to hold it during the applying of the glue process). New jig should address these areas. Honeycomb core gluing - we should cut the honeycomb into smaller pieces and see if this gives better gluing quality. Need to design a proper glue bath for gluing the top skin. (Features like a Al plate with 0.5mm depth recess, and some reference features for Stave core partial assembly, and some indicators show where the cooling pipe locates etc) The way we did for trimming stave to size worked all right. All the tooling (e.g locations blocks and C channel clamping pieces, etc) need to be clearly marked, for correct position on jig.

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Cooling pipe gluing jig