Assessment of the effect of impact damage in composites: Some problems and answers

In order to provide through-life support for structural components, fabricated from advanced composite materials, it is desirable to establish a damage tolerance methodology. The availability of this methodology would greatly aid the design of safe, efficient composite structures as well as their management in service. There are, however, many difficulties in meeting this objective, including the multiplicity of failure modes in the composites, the numerous types of potentially significant defects which may arise during manufacture or in service, and the sensitivity to moisture and temperature. This paper discusses the analysis and testing of impact damage composite laminates. Selected experimental studies in the literature are briefly discussed. It is shown that uniaxial S-N curves for damaged laminates have a generic shape with a pronounced threshold level. Indeed, it is clear that further research is needed to understand the physical reasons for such a threshold value.