environmental effects on composite structure
You are partly correct Muduckace. It is well known that composite materials absorb moisture in humid environments and that moisture reduces the glass transition temperature, the temperature at which the resin system stops being a glassy, rigid material and becomes a soft rubbery material. This has the effect of reducing the strength and elastic modulus at high temperatures.
These effects are so well known that the reduced properties are factored into the design. There is also a requirement that the Tg is well above the maximum operating temperature. Further, apart from areas adjacent to engines, the temperature cycle seen by a civilian airliner will be such that this should not be an issue. The certification basis of the current FARs, together with the FAA Advisory Circular AC-20-107A should be adequate for composite structures.
However, the same can not be said for adhesive bonded structures because the current FARs and AC 20-107A do not prevent production of adhesive bonds which are resistant to hydration, and that hydration is accelerated by hot, humid environments.
Was the quick 787 repair bonded or fastened?
Regards
blakmax
Last edited by blakmax; 5th Sep 2009 at 23:49.
Reason: oops Tg "below" T Max-op instead of above