Study On Thermo-mechanical Behaviors Of Woven Fabric Reinforced Shape Memory Polymer Composites

Known as new functional materials with shape memory effect,shape memory polymers(SMPs)are able to return to the permanent shape from a temporary one upon exposure to certain external excitation.However,the intrinsicdeficienciesof SMPs like low strength,low stiffness and small recovery stress have significantly restricted theapplication.Reinforcement of woven fabric can not only remarkably increase the strength of SMPs but also effectively homogenize the in-plane mechanical properties of the composites and improve the out-of-plane performance.So far,there is still little research on the thermo-mechanical properties of woven fabric reinforced shape memory polymer composites(woven SMPCs).In this paper,the thermo-mechanical behaviors of woven SMPCs are studied by theoretical derivation and numerical calculation.Firstly,the multi-scale models of 2D and 3D woven SMPCs are established.And a new parametric modeling method of 3D woven composites of which the weaving densities and packing factor of fiber in the yarn are main parameters is proposed based on previous studies and photomicrographs.Secondly,the influences of the stretch modulus and bending modulus of the reinforcing layer on the shape memory behaviorof 2D woven SMPCs are investigated.A five-layer model is used to study the effects on the thermo-mechanical performances of the position of the reinforcing layer in the thickness direction under flexural loading.It is shown that the shape memory performance of 2D woven SMPCs under pure bending condition is only related to the bending modulus of the reinforcing layer.And the shape fixation ratio and recovery stress are higher when the reinforcing layer is on the tension side.Furthermore,based on the multi-scale model,the thermo-viscoelastic properties of yarns are obtained from the viscoelastic parameters of acrylate network matrix and the elastic constants of fibers.A programming method of user's material subroutine of ABAQUS for orthotropic thermo-viscoelastic material is proposed based on the constitutive relationship.The effects of external loading and weaving densities on viscoelastic properties of 3D woven SMPCs are researched in detail.Finally,the shape memory behavior of 3D woven SMPCs is further discussed based on the thermo-viscoelastic properties above.The free recovery and constrained recovery procedures are carried out to study the influences of external loading and weaving densities on shape memory performances of 3D woven SMPCs.