Experimental study on nonlinearity of unidirectional carbon fibre-reinforced shape memory polymer composites

A comprehensive and detailed experimental study has been conducted on shape memory polymer composites (SMPCs) with different reinforcements, thicknesses, fibre volume fractions and distributions. Monotonic test results show temperature-dependent mechanical properties. Cyclic loading–unloading tests, including constant and incremental strain-controlled tests, were conducted in three-point bending and transverse tension to investigate softening and reusable characteristics. The fibre postbuckling behaviour for samples undergoing bending deformation combines geometrical and material nonlinearities. While for transverse tension, all possible sources of nonlinearity are due to the material responses. The energy properties were highly fibre volume fraction- and strain amplitude-dependent. The stiffness was also sensitive to the degree of fibre clustering. The focus of this work is not on the examination of basic elastic constants, but on the nonlinear and reusable responses of SMPCs, which can be used for both the design of aerospace deployable mechanisms and analyses of the damage process.