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