Since the shape memory and recovery characteristics of shape memory polymers (SMPs) are realized by a certain thermalmechanical cycling process

the thermomechanical constitutive equations are critical for predicting the deformation and recovery of this class of materials at different constraint conditions.In this study

a new physical-based

temperature and timedependent constitutive model was proposed.The crystallization theory was used for reference to describe the frozen fraction of SMPs

and the frozen retardant time at the cooling/heating cycle was considered in the constitutive equations.In order to consider both matrix/reinforcement and reinforcement/reinforcement actions during the shape changing process

MoriTanaka approach was used to predict the effective elastic modulus.Moreover

the thermal- and mechanicalfrozen fractions as a function of the temperature were compared.The mechanical strain determines the shape storage characteristics of SMPs and will be frozen mostly at the temperature to be lower than the shape changing temperatures (Ttran) of SMPs.The thermal strain

however

mainly determines the instant recovery stress of SMPs during the shape recovery stage

and the part accumulated at Ttran can hardly be frozen.Hence

the values of the mechanical and thermal frozen fractions at the same temperature are different.Finally

the stress responses at different strain conditions during the cooling process were predicted by the new model

and the results exhibited to be much agreeable with the testing values.