Effect Of Strain Rate On The Mechanical Properties Of The Shape Memory Polymer

As a new type of functional memory material which was developed after shape memory alloy and shape memory ceramics,shape memory polymer(SMP)has many advantages,such as low density,high deformation recovery rate,wide temperature adaptability,good biocompatibility and low cost.With a high potential utilization,the SMP can be widely used into a variety of field such as medical,biological and aerospace fields.As a polymeric material,SMP has strong temperature-dependence and rate-dependence characteristics.Thus,in order to apply it into engineering industry,it is very important to understand its thermodynamic properties under different temperatures and different strain-rate conditions.In this paper,both the experimental,theoretical researches and numerical simulations are conducted to analyze the strain-rate effect on the SMP mechanical properties in the range of glass-transition temperature.The details are listed as follows:First,within the range of glass-transition temperature,the different strain-rate effects on the SMP'S mechanical properties are investigated in this paper.The uniaxial tensile test is performed to study the mechanical properties of the shape memory epoxy resin with different loading rates and under different temperature conditions,which provides the basis for analyzing the strain-rate effect;Second,a new parametric equation of shape memory polymer is established.On basis of DMA experimental method,a new material parameter equation is obtained.After compared the outputs with the experimental data,the new equation shows a high fitting degree;Third,the influences of strain-rate and material size on the parameters of the material under different temperature conditions are analyzed.The strain-rate effect on material temperature and material parameters is calculated by the shape memory polymer macroscopic constitutive model and the energy-loss area of tensile curve,which can be also used to analyze whether the strain-rate could accelerate the glass transition process or not.The results show that the strain-rate has a small effect on the material temperature and SMP's temperature-related material parameters;Finally,in this paper the effect of high strain rate on SMP's mechanical properties are also studied.The Prony series fitting method is summarized;the finite element simulation of the uniaxial tension of SMP in small strain rate is simulated,which proves the simulation method is feasible.Then,the theoretical analysis and finite element simulation of the large strain rate on the shape memory polymer's mechanical properties are compared,and it is pointed out that the effect of high strain rate is negligible.The obtained results in this paper are important to have a good understanding of the SMP's mechanical properties and the temperature-determined glass-transition progress in complex engineering applications.