Cohesive zone models (CZM) and energy-regularised continuum damage mechanics (CDM) models are amongst the most popular tools for the analysis of damage and fracture in composites. Where fracture processes need to be modelled in detail, e.g. meso-scale analyses of delamination and transverse cracking in laminates, CZM can be used to represent the onset and growth of individual cracks and to ensure their inter-element continuity. This requires either the meshing of potential crack paths, the use of re-meshing schemes, or the introduction of mesh-independent discontinuity models (e.g. XFEM). On the other hand, if the structural behaviour of interest can still be reproduced after further homogenisation and some loss of detail, then CDM models may be more viable options.

However, the aerospace industry still relies heavily on the ‘physical testing pyramid’ for the design and certification of compositestructures, since large scale tests cannot safely be augmented or replaced by virtual testing. One of the reasons is that composite structures display a myriad of different damage mechanisms across multiple length scales, which results in conflicting requirements in terms of numerical modelling.

This seminar will discuss ongoing efforts by the Composites UTC to develop modelling tools suitable for the virtual testing of composite components in aero-engine applications, where stringent safety requirements and complexities in terms of geometries, loading and environmental conditions result in very challenging problems. Techniques being pursued include mesh-independent CZM implementations, smeared crack models with inter-element continuity, variable-kinematics CZM formulations and multi-scale analysis techniques.