An energy based damage mechanics approach to modelling impact onto woven composite materials: Part II. Experimental and numerical results

Laminated composites have found an increasing use in many industries, particularly in transport, e.g. in the design of aircraft, helicopters, boats, cars, etc. Many of these composite components are fabricated from woven carbon based materials, which are more drapeable than conventional uni-directional (UD) composites, but generally have less stiffness and strength. To accurately design such components or structures to withstand severe external loadings, such as high velocity impact or a crash event, is conceptually a difficult task for the composite designer. Unlike metallic components, which can yield and dissipate energy via plasticity, composites can only dissipate energy by different damage or fracturing processes, which usually degrade the stiffness of the structural component.This paper presents the application of the energy based damage model, previously described [Iannucci L, Willows M. An energy based damage mechanics approach to modelling impact onto woven composite materials: Part I Numerical model, Composites A, in press, doi:10.1016/j.compositesa.2005.12.013], suitable for modelling the progressive failure of woven carbon composites under high strain loading. The approach is based on a damage mechanics methodology, and has been implemented into the explicit dynamic DYNA3D code for plane stress shell elements. An interface modelling strategy is also presented to determine the corresponding maximum delamination envelope during a dynamic simulation.The form of the stress–strain–damage curve for woven carbon and the relevance of experimentally measured material damage constants are discussed. The simulation results are compared to three CRAG impact experimental tests at three distinct energy levels. A detailed parameter study is performed on the magnitude of the intralaminar energy release rate used to propagate the damage in woven carbon composites. Conclusions are drawn on the assumed form of the damage evolution curve, and its applicability to stochastic modelling techniques.