FIBRE-BRIDGING IN DELAMINATION: MODELING AND EXPERIMENTAL RESULTS

摘要

Test results for the delamination response of unidirectional polymer matrix composites in monotonic and cyclic loading are often heavily influenced by low-angle bridging fibres. Although these represent a relatively low force mechanism, the compliance of the standard double cantilever beam specimen allows them to have a very large effect on the measured results. In particular, bridging in tests tends to give rise to pronounced R-curve responses [1] and generally slower fatigue delamination growth rates than would be observed were the bridging not to occur. Since fibre-bridging cannot be guaranteed in service, data affected by bridging is generally regarded as being useless, and testing focuses on obtaining initiation values for fatigue loading and toughness data. This approach, while resulting in safe designs, is wasteful of test specimens, and prevents the implementation of damage tolerant design approaches, which have proved so important in designing for longevity in metal airframe structures. The work presented in this paper is motivated by the desire to make more complete use of the available delamination test data, particular with regard to the fatigue delamination propagation response. In addition, the work aims to provide a means to identify the effect of temperature on the fatigue and fracture response of a polymer matrix composite system in order to guide approaches to accelerated testing.