Keywords: composite, model, modes, damage, finite element.

The number of engineering applications using composite materials in light-weight structures and, in particular, in the aerospace industry has significantly increased in the last decade, mainly due to the large strength-weight ratio that they provide. The modelling of these materials and their damage evolution is also of an increasing interest. However, the mixed mode of failure in composite materials often result in sophisticated damage models.

So far, the modelling schemes are mainly centered on two main tendencies. The first one is concerned with the development of quadratic stress-based criteria [1]. The second trend proposes a progressive evolution of the damage, although most of these last approaches are limited to two-dimensional models, assuming generally a plane stress state in the laminae [2].

This paper presents a damage model for fibre composite materials. The first stages of this model were partially published as a work-in-progress notes in Curiel Sosa et al. [3]. The composite is modelled in a three-dimensional context whereby the anisotropy introduced by the mixed-modes damage is conveniently assessed. Therefore, the constitutive law as well as the damage formulation are described in a three-dimensional framework. The composite dynamic behaviour is modelled by a growth-of-damage and strain rate dependence. A homogenised orthotropic composite material subjected to distinct failure modes is assumed. Each mode is modelled by means of a growth function and a directional damage evolution that foresees the inelastic behaviour preceding the total failure of the composite structure.

The momentum equations resulting from the finite element discretisation include the inertia term in order to simulate the transient response of the composite structure. The implementation is performed in an explicit integration scheme for nonlinear finite element analysis [4].

1

M.J. Hinton, A.S. Kaddour, P.D. Soden, "A further assessment of the predictive capabilities of current failure theories for composite laminates: Comparison with experimental evidence", Compos Sci Technol, 64 (3-4), 549-588, 2004. doi:10.1016/S0266-3538(03)00227-6

2

C.E. Harris, T.W. Coats, D.H. Allen, D.C. Lo, "A progressive damage model and analysis methodology for predicting the residual strength of composite laminates", J. Compos. Technol. Res., 29, 926-981, 1995.

3

J.L. Curiel Sosa, N. Petrinic, J. Wiegand, "A three-dimensional progressive damage model for fibre-composite materials", Mechanics Research Communications, 35 (4), 219-221, 2008. doi:10.1016/j.mechrescom.2008.01.009

4

J.L. Curiel Sosa, E. de Souza Neto, D.R.J. Owen, "A combined implicit-explicit algorithm in time for non-linear finite element analysis", Commun. Numer. Meth. Engng., 22, 63-75, 2006. doi:10.1002/cnm.804

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