Numerical considerations for the implementation of a comprehensive composite damage model

A comprehensive continuum damage mechanics model [1] had been developed to capture the detailed behaviour of a composite structure under a crushing load. This paper explores some of the difficulties encountered in the implementation of this model and their mitigation. The use of reduced integration element and a strain softening model both negatively affect the accuracy and stability of the simulation. Damage localisation effects demanded an accurate measure of characteristic length. A robust algorithm for determining the characteristic length was implemented. Testing showed that this algorithm produced marked improvements over the use of the default characteristic length provided by Abaqus. Zero-energy or hourglass modes, in reduced integration elements, led to reduced resistance to bending. This was compounded by the strain softening model, which led to the formation of elements with little resistance to deformation that could invert if left unchecked. It was shown, through benchmark testing, that by deleting elements with excess distortions and controlling the mesh using inbuilt distortion/hourglass controls, these issues can be alleviated. These techniques contributed significantly to the viability and usability of the damage model.