This paper presents a computational technique for the prediction of fatigue-driven delamination growth in composite materials. The interface element, which has been extensively applied to predict delamination growth due to static loading, has been modified to incorporate the effects of cyclic loading. Using a damage mechanics formulation, the constitutive law for the interface element has been extended by incorporating a modified version of a continuum fatigue damage model. The paper presents details of the fatigue degradation strategy and examples of the predicted fatigue delamination growth in mode I, mode II and mixed mode I/II are presented to demonstrate that the numerical model mimics the Paris law behaviour usually observed in experimental testing

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The most common technique for the numerical implementation of peridynamic theory is based on a mesh-free approach, in which the whole body is discretized with a uniform grid and a constant horizon. As a consequence of that computational resources may not be used efficiently. The present work proposes adaptive refinement algorithms for 2D peridynamic grids. That is an essential component to generate a concurrent multiscale model within a unified approach. Adaptive grid refinement is here applied to the study of dynamic crack propagation in two dimensional brittle materials. Refinement is activated by using a new trigger concept based on the damage state of the material, coupled with the more traditional energy based trigger, already proposed in the literature. We present as well a method, to generate the nodes in the refined zone, which is suitable for an efficient numerical implementation. Moreover, strategies for the mitigation of spurious reflections and distortions of elastic waves due to the use of a nonuniform grid are presented. Finally several examples of crack propagation in planar problems are presented, they illustrate the potentialities of the proposed algorithms and the good agreement of the numerical results with experimental data.

This paper discusses different types of implicit time integration algorithms for the dynamics of spatial beams. The algorithms are based on a form of co-rotational technique which is external to the element. Both end-point and mid-point formulations are presented. The latter can be considered as an`approximately energy conserving algorithm'. A new method is described for introducing numerical damping. Finally some numerical examples are presented in order to illustrate the differences in performance of the different integration schemes.

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This paper investigates robustness and efficiency of a method for the numerical simulation of fatigue driven delamination growth in laminated composites. The method is based on the fatigue degradation of a bilinear interface element and the paper studies the dependence of the predicted behaviour on the interface element size, Delta l, and the number of cycles per increment, Delta N. It is concluded that the value of Delta N must be small enough to ensure that at least two increments are required to advance the crack by Delta l. It is also shown that Delta l must be sufficiently small so that at least two interface elements lie in the cohesive zone ahead of the crack tip. The paper also proposes extensions of the model to include a non-zero minimum cyclic load value and an improved algorithm for mixed-mode fatigue driven delamination growth