Behavior of composites under mutiaxial cyclic loading

工程部件在使用过程中经常受到重复（疲劳）载荷的影响。在这些循环载荷下，组件在低于静态载荷的情况下失效。常见的结构不连续（缺口），如螺栓孔、键槽、螺纹根等，会进一步降低这些部件的寿命。由于疲劳导致的过早失效已经严重损害了人类安全和工业经济。因此，大型工业部门一直在努力不断解决他们用于预测其部件使用寿命的模型中的不确定性。在实际应用中，大多数构件都要承受各方向（多轴）载荷，因此适用于金属的分析疲劳寿命预测模型还处于发展阶段。这种设计工具的发展也落后于更先进的材料，如金属基或纤维增强复合材料的发展。这些材料具有许多优于金属的性能，因此受到航空航天、汽车和基础设施等大型工业部门的追捧。然而，由于缺乏多轴疲劳设计策略，这些材料并没有充分发挥其潜力，在实践中它们的使用仍然受到阻碍。该研究计划的最终目标是开发和实验验证疲劳分析工具，这些工具可用于预测缺口部件在多轴循环载荷下的寿命。该研究将重点关注这些工具在颗粒金属基复合材料和碳纤维增强聚合物方面的进步。这项工作将有助于为行业提供必要的信心，通过提供工具来评估复合材料部件在实践中的可靠性、安全性和使用寿命，从而利用所研究的复合材料的有益材料特性。

Engineering components are routinely subjected to repetitive (fatigue) loads in service.  Under these cyclic loads, components fail at loads lower than those that would cause failure if applied statically.  Common structural discontinuities (notches) such as bolt holes, keyways, thread roots, etc., act to further reduce the life of these components.  Premature failures due to fatigue have seriously compromised both human safety and the industrial economy.  Therefore, there has been a great effort in large industrial sectors to continuously address the uncertainties in the models they use to predict the service life of their components.    The majority of components in practice are subjected to loads applied in all directions (multiaxial), for which analytical fatigue life prediction models applicable to metals are still in their evolution stage.  The development of such competent design tools has also lagged behind the development of more advanced materials such as metal matrix or fiber-reinforced composites.  These materials have many properties that are superior to metals and are therefore being sought after by large industrial sectors such as the aerospace, automotive, and infrastructure industries.  However, as a result of the lack of multiaxial fatigue design strategies, the materials are not being used to their full potential and their use is still met with reluctance in practice.    The end goal of this research program is to develop and experimentally validate fatigue analyses tools that can be used to predict the life of notched components subjected to multiaxial cyclic loading.  The research will focus on the advancement of these tools for particulate metal matrix composites and carbon fiber reinforced polymers.  The work will contribute to providing the confidence necessary for the industry to take advantage of the beneficial material properties of the composites studied by providing tools to evaluate the reliability, the safety and the service life of composite components in practice.