Study On Recovery Behaviors Of Shape Memory Polymer Composites

Shape memory polymers(SMPs)are a novel kind of promising smart materials,and their outstanding characteristic is shape memory effect.SMPs can recovery the programmed shape in response to external stimulus such as heat,light,electricity,magnetism and moisture.SMPs have the advantages of light weight,large shape deformability and low cost,however the mechanical properties of SMPs are relatively low.Shape memory polymer composites(SMPCs)can be fabricated by adding particles,fibers or fabrics into SMP matrix,and SMPCs are reinforced while good shape memory capabilities are kept.In the paper,the thermomechanical properties and shape memory behaviors of SMPs and their composites are studied.Firstly,a thermomechanical constitutive model is developed based on the thermoviscoelastic theory.The generalized Maxwell model is employed to describe the viscoelastic properties,and the Neo-Hookean model is applied to characterize the hyperelastic behaviors of SMPs.Then,the thermomechanical cycle is simulated in ABAQUS,and the effect of the heating rate is studied in the free recovery step.Secondly,the free recovery behaviors of chopped fiber reinforced SMPCs are investigated by the modified standard linear solid model.The KWW stretched exponential factor is used to modify the model and the temperature dependent modulus is obtained by a Prony series form and the time temperature equivalence principle.Then,the relationship between shape recovery ratio and temperature is derived.Finally,a thermoviscoelastic finite deformation constitutive model is developed to investigate the thermomechanical properties and shape recovery behaviors of particle reinforced SMPCs based on the generalized three-element model.The model is incorporated with the modified Adam-Gibbs model and the Eyring model to describe the structural relaxation and yielding behaviors.Then,the model is used to estimate the uniaxial tensile stress response and the relationship between the free recovery strain and temperature.Furthermore,the recovery behaviors at different heating rates are predicted by the model.