Damage growth and failure in composites

复合材料在商用飞机结构中越来越大规模的使用，意味着我们正在进入一个新的时代。因此，解决与复合材料相关的基本问题的需求现在比以往任何时候都更加重要。然而，我们仍然有许多不理解的地方。目前，学术界还没有就如何以一种一贯准确但保守的方式预测实际结构的失效达成共识，而不是显着和不可接受的保守。然而，工业界正在设计、制造和认证比铝合金飞机更轻的飞机。理想情况下，学术方面的基本发展将使我们能够为此类工业设计和分析提供与断裂力学和塑性理论为金属设计和分析提供的相同水平的共识和开放知识支持。 我们一直无法发展适当的失效准则的一个主要原因是，它一直是非常困难的，在大型结构中使用小样本复制失败。 因此，在本项目中，我们将开发和使用一系列测试几何形状，这些几何形状涵盖了表征纤维增强聚合物基复合材料层合板在拉伸、压缩和横向冲击中失效所需的一系列特征和尺寸。 使用两种或更多种材料类型和一系列铺层来触发不同的失效事件和序列，我们将跟踪损伤的演变和随之而来的机械响应。 利用这些信息，我们将创建一个框架来解释损伤增长的驱动力和损伤对材料刚度的影响方面的损伤历史的演变。 我们将确保描述在广泛的几何和材料条件下保持一致。 从这个结构材料表征的结果将被用来行使其他程序下开发的数值损伤模型，与最终目的是提供设计师与有效的设计工具，以及标准的方法来表征材料的有效性和准确性。

The increasingly large scale use of composite materials in commercial aircraft structures means that we are now entering a new era. Therefore, the need to solve fundamental problems relating to composite materials is now even more important than ever before. However, there is much that we still do not understand. There is currently no consensus agreement in the academic world on how to predict failure in realistic structures in a consistently accurate yet conservative manner, without being significantly and unacceptably conservative. And yet industry is designing, building and certifying aircraft that are lighter than their aluminum predecessors. Ideally, fundamental developments on the academic side would allow us to provide such industrial design and analysis with the same level of consensus and open knowledge support as provided for metals design and analysis with fracture mechanics and plasticity theory. One major reason that we have been unable to develop proper failure criteria is that it has been very difficult to replicate failure in large structures using small specimens. Therefore, in this program we will be developing and using a family of test geometries spanning a range of features and sizes needed to characterize the failure of fibre reinforced polymer matrix composite laminates in tension, compression and tranverse impact. Using two or more material types and a range of lay-ups to trigger different failure events and sequences, we will be tracking the evolution of damage and the consequent mechanical response. Using this information, we will create a framework to explain the evolution of the damage history in terms of the driving force for damage growth and the effect of that damage on the stiffness of the material. We will ensure that the description is consistent across a wide range of geometrical and material conditions. The results from this structured materials characterization will be used to exercise numerical damage models developed under other programs, with the final intention being to provide designers with efficient and valid design tools, as well as standard methods to characterize materials efficiently and accurately.