On the importance of finite element mesh alignment along the fibre direction for modelling damage in fibre-reinforced polymer composite laminates

A finite element mesh, aligned along the fibre direction, has often been purported to yield more accurate results in the modelling of damage in composite structures constructed from unidirectional fibre reinforced polymer laminates. However, there has been a lack of a systematic assessment of this approach. This issue is addressed through modelling a selection of test cases; (i) end notched tension (ENT) coupons, (ii) simple tensile/compressive specimens, (iii) open-hole tension (OHT), (iv) low velocity impact (LVI) and (v) compression-after-impact (CAI) of laminated plates. In each case, two models were constructed, one using a uniform mesh, aligned with the global coordinate system, and independent of the fibre direction, and the other where each ply mesh was aligned along the fibre direction. In both cases the local material axes in each ply were correctly represented. Results show that a finite element mesh aligned along the fibre direction plays an important role in the prediction of damage, particularly in the presence of a crack. However, when matrix crack paths are not established a priori, or may not be the dominant damage mode, fibre mesh alignment is unnecessary. Rather, long-established approaches of refined meshes, robust damage models and well-defined material data and boundary conditions, are shown to be sufficient requirements.