Composite design using a damage mechanics methodology

Current predictive techniques for the analysis of composite structures and components near their ultimate strength are simplistic, using basic damage functions and traditional failure envelopes to determine the degree of damage in some arbitrary composite component or structure. Similarly, the design procedure usually assumes the composite structure remains elastic throughout any potential applied loading. The analysis methodology proposed in this paper reflects a state-of-the-art technique that can be used to model a wide range of problems from extreme events, such as an explosion, to nonlinear static delamination problems which can occur near discontinuities or free edges. As damage is cumulative, the technique allows initial or/and post-impact static loads to be applied to the composite structure or component, thus allowing a cradle-to-grave design methodology. Results are presented for a high velocity impact event on a woven glass composite and for delamination growth predictions for a DCB specimen, elastic laminate stresses are compared to traditional laminate composite design programs, such as LAP, to illustrate the capability of modelling non-linear static composite problems, without the need for a separate implicit FE code.