Failure mechanisms and deployment accuracy of elastic-memory composites

Elastic-memory composites (EMCs) is a class of polymeric composites that can be folded into a very compact shape and later deployed to the original shape upon reheating. They have significant potential in developing large deployable structures greater than 10 m in size that can be stowed in a small launch vehicle and deployed in space to predetermined levels of precision. Generally, the composite is folded by heating it above the glass transition temperature of the resin. The primary deformation mode that allows EMCs to achieve significantly higher effective strains than traditional composites is microbuckling of the compressed fibers. The magnitude of this microbuckling dictates whether the laminate behaves elastically or if the laminate exhibits material failure such as fiber breakage, or fiber kinking. This paper explores the micromechanics of both types of fiber-deformation modes associated with the bending of such soft-resin composites. An analysis method is developed and correlated with experimental data to provide an estimate for the level of folding strain that a soft-resin laminate can achieve based on microbuckling-induced material failure. Additionally, insight is provided into the effects of fiber and matrix material properties on the formation and magnitude of the kink mode. Tests were also conducted to determine the deployment accuracy after a number of folding/deployment cycles to help design deployable sensor structures with these materials.