水敏形状记忆聚合物发泡材料的溶剂-温度耦合力学行为及其数值模拟

The shape recovery of water/chemo-responsive shape memory polymer (WSMP) can be triggered upon immersing into water or other solvents without heating. As a consequence, WSMPs have a wide potential application prospects in both biomedical and engineering fields. However, the shape recovery response of buck WSMPs triggered by solvents is quite slow due to the diffusion process of solvents into buck WSMPs is time-consuming, which limits the application of WSMPs. In this project, the coupled water-temperature shape memory behaviors of WSMP foams will be systematically investigated. Firstly, WSMP foams are prepared with batch foaming process, Secondly, we plan to set up an experimental platform to systemically investigate the coupled solvent-temperature-mechanical shape memory behaviors of both buck WSMP materials and that with various foam structures. Thirdly, a finite deformation constitutive model based on both the phase-transition shape memory theory, the Gordon–Taylor theory and the free-volume theory is established to capture the coupled solvent-temperature-mechanical shape memory behaviors of WSMPs. Lastly, Voronoi method and Kelvin unit cell model are used to construct the detailed meso-scale structures of WSMP foams and the water/solvent-triggered shape memory behaviors of WSMP foams and the diffusion process of solvents will be simulated numerically with FEM, the foam structure of WSMPs can be optimized to obtain the best performance. These investigations will help in laying the foundation for the applications of WSMP foams.

水敏形状记忆聚合物可以在水或其它小分子溶剂刺激下实现变形恢复，在生物医学和工程领域具有广阔的应用前景，是目前智能材料研究的热点之一。但由于其块体材料存在溶剂渗入过程耗时长，形状记忆响应缓慢等问题，限制了其工程化应用。针对上述问题，本项目开展“形状记忆水敏聚合物发泡材料的溶剂-温度耦合力学行为及其数值模拟”的研究，首先采用间歇式快速降压法制备水敏形状记忆聚合物发泡材料，探索泡孔结构可调控的工艺；其次搭建溶剂-温度-力耦合测试平台，开展不同泡孔形貌形状记忆聚合物在溶剂-温度-力多场耦合下力学性能研究；并构建基于相变的溶剂-温度-力多场耦合三维大变形形状记忆本构模型，利用Voronoi算法构建泡孔结构的细观结构模型，对水敏形状记忆力学行为和溶剂扩散过程开展数值仿真研究。从而实现水敏形状记忆聚合物的多孔结构与形状记忆性能的最优化设计。这些基础研究工作将为水敏形状记忆聚合物发泡材料的应用奠定基础。

聚乳酸形状记忆发泡结构具有轻质、形状记忆变形量与形变回复大、弹性模量大、结构和力学性能可调控、生物相容性好、可降解等优点，有望在航空航天、生物医学等领域得到广泛应用。以聚乳酸聚合物发泡材料为研究对象，开展溶剂-温度耦合力学行为的制备、形状记忆力学行为、本构理论和数值仿真研究，系统研究模量、结构、形状记忆变形响应速度的影响因素及规律。本项目主要研究工作包括：.（1）利用溶剂共混法制备聚乳酸基形状记忆聚合物样品，引入聚乙二醇（PEG）作为增塑剂，对PLA/PEG其力学性能、热学性能和形状记忆循环性能开展系统研究；.（2）搭建了超临界CO2间歇式降压法制备聚合物发泡结构制备平台，成功制备了一系列具有形状记忆性能的聚乳酸发泡材料，并对发泡结构进行表征和宏观力学性能测试，对聚乳酸基形状记忆发泡材料制备工艺开展了探索；.（3）搭建了温度-力-溶剂耦合测试平台，对聚乳酸发泡材料的形状记忆力学行为开展系统研究，实验结果表明制备工艺对泡孔结构和形状记忆性能都有显著影响；.（4）建立一个基于相变的三维大变形本构模型，与实验结果进行对比表明该模型能够准确描述聚乳酸基形状记忆材料力学行为；.（5）建立了一套利用Voronoi算法生成发泡结构全开孔、半开孔3D模型的流程，并利用该模型开展有限元计算机仿真，预测泡孔率、开孔率等结构参数对于发泡结构宏观力学性能的影响。.本项目研究为优化设计形状记忆泡孔结构与性能优化提供理论依据与指导，具有较好的学术价值与应用价值。