Carbon Fiber Reinforced Shape Memory Polymer Composites

In this paper we present results on the deformation of carbon fiber reinforced shape memory polymer matrix composites for deployable space structure applications. The composites were processed using resin transfer molding or a pre-impregnated (pre-preg) laminate press, with both satin and plain weave fiber architectures. The polymer matrix glass transition temperature, T g , was approximately 95°C. Composite specimens were bent to specific radii at T = 120°C, and cooled while constrained to a temperature of 25°C, which left them frozen in the bent state. Heating the specimens above T g caused the composites to return to their original unbent shape with up to 95% recovery based on bend angle. The effect of constraint hold times up to 350 hours on the recoverability was found to be negligible. Microscopic investigations revealed that the dominant local deformation mode of the composites was buckling of the carbon fibers on the inner surface of the bend. Localized buckling out of the material plane lead to detrimental interfacial matrix failure while dispersed in-plane buckling was elastic and non-damaging. A clear path for tailoring the shape memory polymer composites to facilitate in-plane elastic buckling is presented and tested. The improved materials can bend to local radii of curvature, R, of 1.6 mm with full recoverability and negligible local damage.