sigma 3-3
Remember sigma 3-3, that is the short transverse and I don't care how strong in-plane capabilities of composites are, you only have lousy epoxy for out-of plane sigma 3-3. There has been some nonsense spoken of this thread re toughness. so beware. Those who understand composites know this issue, but clearly a lot of pprune folks don't. The static sigma 3-3 is around 5 ksi and epoxies are lousy in fatigue, just as aluminums are, so assume at fatigue allowable of 40% of static and you end up with an tensile allowable of 2 KSI, which is close to zero. Remember the lousy recent 787 wing failure with out-of-plane loads explanations in Boeing statements. Just remember that CF layups are good in sigma 1-1 and sigma 2-2 if properly designed, but you have that dangerous sigma 3-3 matrix dominated issue at all times.
Last edited by amicus; 29th Jun 2009 at 01:50.
Reason: Correction of source