Long-term durability of polymer composites

聚合物复合材料越来越多地应用于航空航天和非航空航天领域的结构应用中。即将推出的波音787梦幻客机，聚合物复合材料占其结构重量的50%以上，是这一趋势的最新亮点。其他例子有复合材料涡轮叶片、复合材料桥面等。由于聚合物基质的粘弹性，复合材料在服役期间会发生随时间变化的弹性(蠕变)和强度(蠕变断裂)退化。额外的贡献来自随着时间的推移在层板/层压板内发展的损伤。为了在承重结构应用中可靠地设计和应用聚合物复合材料，需要对这种退化过程有很好的理解和量化的能力。虽然过去的研究已经大大提高了这一领域的知识，但还需要进行更多的基础工作。因此，这项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。这项研究将建立各种损伤模式的时间依赖演化模型，及其对聚合物复合材料层合板的弹性和强度的影响。该模型将使用来自多个层合板类型的实验结果进行验证。用户将能够使用该模型来预测结构复合材料结构在使用寿命期间的退化程度，该模型具有层合板的基本构建块的特性。这一研究项目的创新之处在于新的基础知识(如延迟断裂准则、各种服役参数对蠕变、蠕变断裂和时变损伤演化的交互影响、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。预期的影响是丰富重点领域(复合材料的长期耐久性)，全面了解和促进承重复合材料结构的可靠设计和应用。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.