Asymptotic Modeling of Mixed Mode Delamination Initiation in Arbitrarily Oriented Composite Laminate

The scope of the work is to deal with the asymptotically correct modeling of delamination initiation and calculate the delamination initiation life. Concept of interface elements is chosen so that they can easily be incorporated with in the Variational Asymptotic Frame work and damage initiation is captured in one single coherent simulation. Furthermore, a relative displacement-based fatigue damage model was integrated with the cohesive zone model to simulate the deleterious influence of the fatigue loading at the interfaces. The usage of the interface based analysis requires the calculation of the relative displacements. The work uses the Variational Asymptotic method (VAM) as a platform to generate the relative displacements, which is considered as a parameter for the damage variable. The evolution of the damage variable is expressed as a function of the fatigue cycles. The formulation is applied to the short beam shear test and the number of cycles for the delamination initiation predicted and had shown good correlation with the experimental data as available from the literature 1]. A comparison between the Variational approach and by explicit FEM is also done and conclusions were drawn