Hi all, 

It's hard to say for sure because the biaxial glass (and possibly the carbon?) are not supplied by us but it does possibly point to something on the outside of the glass fabric that's encouraging delamination. You say the glass 'isn't new' so could it perhaps have some contamination on the outer layer; moisture ingress or silicone/oil mist contamination from a workshop environment?

As Warren says, you'd be amazed by how easily layers of reinforcement will delaminate from eachother; there's prcatically no difference between peeling peel-ply off your part and separating layers of laminate, which makes sense when you think about it - in either case you're simply breaking the resin-only bond between two layers of fabric.

It's possible that there is some contamination issue or it's possible that you simply didn't realise how easily laminates can be delaminated. If they don't get 'started' then you generally don't ever encounter a problem. The work of the part is done by the tensile strength (and modulus) of the reinforcement.

Compressed air is lethal when it comes to delaminating composites, much like trying to 'burst' through a laminate using a waterjet (which can delaminate even the best prepregs).

I hope this helps.

Matt Statham
Easy Composites / Carbon Mods - Technical Sales