异常环境下聚合物泡沫材料失效行为的数值模拟及性能评估

As a structural material, polymer foams have important applications in the fields of aeronautics and astronautics. The aging of polymer foam materials has been a hot topic in the abnormal environment of high temperature and so on. It is not enough to carry out the theory research systematically of foam materials under abnormal environment although many researches have tried to solve this problem. Basing on the numerical simulation technique in this project, the service failure behavior of polyurethane foam materials under the conditions of aerobic / anaerobic, limited / free state in the abnormal environment is studied and the failure threoretical models about the structure and performance are constructed in order to grasp the failure mechanism deeply and effectively solve the problem of failure, provide theoretical support. The degradation behavior of polyurethane foam in high temperature environment is investigated systematically by the method of combining the finite element simulation and experiment, and the failure essense of thermal degradation is analyzed by the constructing of degradation model. The stress distribution of the polyurethane foam materials is systematically analyzed in the process of high/low rate vibration, and the numerical model is builded, and the influencing mechanism of material failure in the high/low rate vibration condition is investigated. The failure behavior of the foam materials under the conditions of high temperature and high/low rate vibration is researched, and revealing the evolution law of the bubble morphology and performance of foam materials in the abnormal condition. The implementation of this project will have an important theoretical value for the further development of the new method of aging resistance and high stability of polymer foam under abnormal environment.

聚合物泡沫材料作为结构材料在航空航天等领域有重要应用。在高温等异常环境下聚合物泡沫材料老化一直是热点问题。尽管很多研究试图解决这一问题，但在异常环境下系统开展泡沫材料失效的理论研究尚不充分。本项目基于数值模拟技术，研究有氧/无氧、受限/自由状态等聚氨酯泡沫材料在异常环境下服役失效行为，构建失效组织性能理论模型，为深入掌握失效机理，有效解决失效问题，提供理论支持。项目通过有限元模拟和实验相结合方法，系统研究高温环境下聚氨酯泡沫材料的降解行为，通过降解模型的构建，分析热降解失效的实质；系统分析高/低速振动过程中聚氨酯泡沫材料的应力分布，建立数值模型，考察高/低速振动对材料失效的影响机制；研究在高温及高/低速振动条件下，泡沫材料失效行为，揭示在复杂异常环境下，泡沫材料的泡孔形态及性能演化规律。本项目实施将对进一步发展异常环境下聚合物泡沫材料耐老化和高效稳定性的新方法具有重要的理论价值。

本项目采用实验分析与数值模拟相结合的方式，对复杂异常环境下聚氨酯泡沫材料的失效行为进行了研究。项目首先通过热失重分析(TGA)、差示扫描量热法(DSC)以及傅里叶变换红外光谱(FTIR)等手段对聚氨酯泡沫材料在有/无氧条件下的高温热降解机理进行了表征；通过对热处理前后泡沫材料拉伸性能变化分析，评估了聚氨酯泡沫材料的失效程度，研究了高温环境对泡沫材料失效性能影响规律。通过有限元数值模拟，构建了高温环境下聚氨酯泡沫材料的降解失效模型，通过模型进行了不同环境下的温度变化对聚氨酯泡沫泡体结构及力学性能的影响的理论模拟计算。开展了高/低速振动环境对泡沫材料力学性能影响规律的研究，通过对振动处理前后聚氨酯泡沫压缩性能的表征，研究了自由/受限状态下泡沫材料力学性能的演化规律，通过建立数值模型，对泡沫材料内部应力分布状态及裂纹生长演化进行了探究。系统开展了高温环境及高/低速振动的复杂环境下聚氨酯泡沫材料的组织结构与力学性能的演化规律的研究。通过聚氨酯泡沫微观结构演变分析，建立了泡沫材料的代表体积元(RVE)模型，获得了复杂异常环境下聚氨酯泡沫材料的本构关系，建立了聚氨酯泡沫材料的性能演化模型。基于异常环境下聚氨酯泡沫材料失效结构与性能的表征，揭示了异常环境下聚氨酯泡沫材料失效主要是由于高温导致的基体化学降解与振动导致的泡孔物理开裂协同作用的理论机制。该失效机制能很好的诠释了系统热处理温度的升高、振动幅度的增加、时间的增长以及负载的增加而导致泡体结构的破坏和力学性能的劣化原因。基于微观结构分析构建的RVE模型在嵌入聚氨酯泡沫材料高温振动失效后的力学性能本构方程后，能够较好的对聚氨酯泡沫材料的力学性能演化规律进行预测，该模型的计算结果与实验结果的平均误差小于3%，证明预测模型的可行性。该项目研究成果势必对工程用聚合物泡沫材料在异常环境中的失效预测及防老化失效设计具有重大的科学意义。