Damage growth and failure in composites

点击翻译按钮获取中文摘要

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.