Long-term durability of polymer composites

聚合物复合材料在航空航天和非航空航天领域的结构应用越来越广泛。即将问世的波音787梦幻客机是这一趋势的最新亮点，聚合物复合材料占其结构重量的50%以上。其他的例子还有复合涡轮叶片、复合桥面等。由于聚合物基体的粘弹性，复合材料的模量（蠕变）和强度（蠕变断裂）随时间发生退化。随着时间的推移，层/层压板内部的损伤也会产生额外的影响。在承载结构应用中，聚合物复合材料的可靠设计和应用需要很好地理解这种降解和量化这种降解的能力。虽然过去的研究已经大大提高了这一领域的知识，但还需要额外的基础工作。因此，本研究计划的总体目标是填补这一领域的关键知识空白，并开发一个全面的模型来量化这种退化。提出的研究将建立一个随时间变化的损伤模式演化模型及其对聚合物复合材料层合板模量和强度的影响。该模型将使用来自多个层压板类型的实验结果进行验证。用户将能够将该模型与层压板（层压板的基本构件）的特性一起使用，以预测结构复合材料结构在使用寿命期间的退化程度。本研究项目的新颖之处在于新的基础知识（如延迟断裂准则、各种使用参数对蠕变的交互影响、蠕变破裂和随时间变化的损伤演化、各种损伤模式之间的交互影响、蠕变-疲劳交互作用）和综合预测模型。预期的影响是丰富了重点领域（复合材料的长期耐久性），对承载复合材料结构的可靠设计和应用有了全面的理解和贡献。预计这将使加拿大的航空航天（OEM和MRO）和复合材料工业受益。

Polymer composites are increasingly used in structural applications in both aerospace and non-aerospace applications. The forthcoming Boeing 787 Dreamliner, with polymer composites making-up more than 50% of its structural weight, is the latest highlight of this trend. Other examples are composite turbine blades, composite bridge decks, etc. Owing to the viscoelasticity of the polymer matrix, time-dependent degradation of modulus (creep) and strength (creep rupture) of the composite occurs during service. Additional contribution comes from damage that develops within a lamina / laminate with time. A good understanding of this degradation and ability to quantify this degradation are required for reliable design and application of polymer composites in load bearing structural applications. While past research has advanced the knowledge in this area significantly, additional fundamental work is needed. Hence, the overall objective of this research program is to fill the critical knowledge gaps in this area and develop a comprehensive model to quantify this degradation. The proposed research will develop a model for time-dependent evolution of various damage modes and its effect on modulus and strength of polymer composite laminates. This model will be validated using experimental results from a number of laminate types. A user will be able to use this model with properties of a lamina, the basic builiding block of a laminate, to predict the degree of degradation during the service life of a structural composite structure. The novelty of this research program is in new fundamental knowledge (such as delayed fracture criteria, interactive influence of various service parameters on creep, creep rupture, and time-dependent damage evolution, interactive influence among various damage modes, creep - fatigue interaction) and the comprehensive predictive model. The anticipated impact is enrichment of the focus area (long term durability of composites) with a comprehensive understanding and contribution towards reliable design and application of load bearing composite structures. This is envisaged to benefit aerospace (both OEM and MRO) and composite industries of Canada.