温度梯度对热致型形状记忆聚合物板力学性能的影响

Effect of Temperature Gradient on the Mechanical Properties of Thermotropic Shape Memory Polymer Plates

形状记忆聚合物作为一种新型的智能材料,由于质量轻、成本低以及变形回复率大等优势,已经在航空、医学等领域得到广泛应用.当前对于热致型形状记忆聚合物力学行为的研究,大都集中在整体变温的情况下,随着应用环境的越来越广泛,温度梯度对材料力学性能的影响效果越发重要.论文在均匀应力的假设下,给出材料在不同初始和传热条件下的温度梯度分布情况,结合传热学和热致型形状记忆聚合物相变理论本构模型,分别讨论了不同温度梯度对存储应变、弹性模量等力学性能的影响,通过理论分析和实验数据对比验证了模型正确性.论文研究可为不同导热情况下,对热致型形状记忆聚合物力学行为监测提供思路,也为形状记忆聚合物的进一步工程应用提供理论依据.

As a new type of intelligent material,shape memory polymer has been widely used in aerospace,biomedicine and other fields due to its superiorities in light weight,low cost,and large deformation recovery rate.Among them,the research on the mechanical behavior of thermotropic shape memory polymers mostly focused on the overall temperature change,but the influence of temperature gradient was rarely considered.Existing studies have shown that the temperature gradient has a non-negligible effect on the mechanical properties of materials and the mechanical behavior of engineering structures.Based on the above,under the assumption of uniform stress and combined with the theory of heat transfer and the constitutive model for phase transition of thermo-induced shape memory polymer,a new constitutive relationship considering temperature gradient is proposed.The rationality and accuracy of the model are verified by theoretical analysis and experimental test results.In this work,The effect of continuously changing temperature gradient on the mechanical properties of shape memory polymer in one-dimensional transient heat conduction stage is discussed.The variation of temperature field distribution with time and plate thickness is determined by the finite difference method,and the changes of storage strain,elastic modulus and stress at different thicknesses are analyzed.In the one-dimensional steady-state heat conduction stage,the temperature gradient is a fixed value,the overall state under different boundary conditions is classified,and the changes in stored strain,elastic modulus and stress at different thicknesses in different states are simulated.The results show that when the temperature gradient changes continuously,the mechanical behavior of position changes significantly when its temperature is in the range where the phase transition occurs,so it should be specially monitored.When the temperature gradient is constant,the overall state and mechanical behavior are affected by the boundary temperature conditions.The research in this work can not only provide ideas for monitoring the mechanical behavior of shape memory polymers and the realization of functional gradients under different heat conduction conditions,but also provide a theoretical basis for further engineering applications.