Cure temperature effects on cryogenic microcracking of polymeric composite materials

A model prepreg system was used to evaluate the effect of cure temperature on microcracking in polymeric composite materials exposed to cryogenic cycling. Symmetic and unsymmetric carbon fiber/epoxy laminates were fabricated to examine the development of thermal stresses and microcracks at cryogenic temperatures. The residual strains and theoretical curvatures of the laminates were calculated from the composite properties and correlated with the microcrack density and experimentally observed curvatures. Higher cure temperatures resulted in higher stress free temperatures and residual strains in the laminates, which corresponded directly to increased levels of microcracking.