Long-term performance evaluation and prediction of composite materials and structures

目前，材料的设计是为了满足特定的产品需求，例如，增加刚度，从而减轻重量，或提高耐腐蚀性和疲劳寿命。这种材料的例子是先进复合材料（ACM），其中基体（聚合物，铝/钛）由另一种更硬的材料的纤维或颗粒增强。虽然通过引入第二相材料（例如弹性模量、极限强度和耐腐蚀或抗侵蚀性）可以增强某些机械性能，但其他性能可能会受到不利影响（例如延展性、裂纹萌生、界面损伤、微塑性/蠕变、循环加载下的粘结弱化以及对温度/环境的抵抗力）。因此，在评估这些先进工程材料的全部应用范围之前，需要对其长期行为进行彻底的调查。本研究计划的目的是评估几种有前途的复合材料的长期性能，并开发方法来预测它们在经受复杂（多轴）单调、保持时间和循环载荷以及暴露于自然环境时的响应。我们在这个提案中的重点将放在纤维增强聚合物基复合材料上，因为它们在要求苛刻的应用中不断找到新的用途。所采用的方法将是一种混合性质，包括纳米-微观-中观-宏观尺度的实验研究，以及分析和数值模拟。这种多尺度方法对于理解和预防损伤至关重要，因为损伤始于材料的微观结构。

At present materials are being engineered in response to specific product needs, e.g. increased stiffness which results in reduced weight, or improved corrosion resistance and fatigue lives. Examples of such materials are Advanced Composite Materials (ACM's) where the matrix (polymer, aluminum/titanium) is reinforced by fibres or particles of another stiffer material. While some of the mechanical properties are enhanced by the introduction of a second phase material (e.g. elastic modulus, ultimate strength, and corrosion or erosion resistance) other properties may be affected adversely (e.g. ductility, initiation of cracks, interfacial damage, micro-plasticity/creep, bond weakening under cyclic loading and resistance to temperature / environment). Thus a thorough investigation of the long-term behaviour of these advanced engineered materials is required before the full scope of their application can be assessed.It is the objective of this research proposal to evaluate the long-term performance of a few promising composite materials and to develop methodologies to predict their response when subjected to complex (multiaxial) monotonic,with hold-time, and cyclic loadings, and exposure to the natural environment. Our focus in this proposal would be on the fibre reinforced polymer matrix composites, since they are continuing to find new use in demanding applications.The methodology to be employed will of a hybrid nature involving experimental investigation in nano-micro-meso-macro scales, and analytical and numerical modelling. This multi-scale approach is essential for understanding and prevention of damage, since damage initiates in a material's microstructure.