Research On Strength Properties Of Fiber Reinforced Shape Memory Polymer Composites

Fiber Reinforced Shape memory polymer composites(SMPCs)are the new kind of smart materials,they have a number of potential technical advantages,such as lightweight,cheap,high stiffness,high strength and good shape memory property.Therefore,they have a wide range of applications in the fields of aerospace,biomedicine and intelligent bionics.This paper focuses on the constitutive relationship,shape memory properties and strength limit of SMPCs.The main contents are as follow:Firstly,this paper,based on the polymer phase transition model and the composite bridging model,describes the stress-strain distribution between fiber reinforcement and shape memory polymer matrix,and establishes a thermodynamic constitutive model of unidirectional fiber reinforced SMPCs.The validity of the model is verified by experiments.Based on the model,the stress-strain-temperature relationship is studied during shape memory cycling process.Secondly,based on the theory of polymer strength and different strength theory in composite materials,a method for predicting the strength of SMPCs is proposed under simple loading,and the effects of temperature and fiber content are also studied on the strength characteristics of unidirectional SMPCs.Based on the established model,the influential level of fiber content and temperature on the axial strength,transverse strength and shear strength of SMPCs are predicted.At the same time,the advantages and disadvantages of different predication methods are compared.Finally,based on the maximum stress intensity theory and Tsai-Hill criterion,a method for predicting the strength of SMPCs is proposed under complicated stress state.The effects of temperature,stretching angle and fiber content on the strength characteristics of unidirectional SMPCs are also studied.The results show that the temperature is the main factor that affects the strength of unidirectional SMPCs under complicated loading,and its strength decreases with increasing temperature.With the increase of angle,the strength decreases sharply and then keeps gentle.However,the impact of fiber content is greater at low temperatures and negligible at high temperatures.