Analysis of delamination propagation in composite structures

Numerical investigation of specimens fracture process of composite materials with delamination under quasistatic and fatigue case is performed. Objective of this work is to study regularities of delamination propagation in laminated composites under static and cyclic loading. Finite element method is the most appropriate apparatus for modeling of delamination propagation process at actual structure considering geometry complexity and loading conditions. Wherein CZM (cohesive zone model) is useful to investigate considered problem. Basing on the contact interaction of shell-layers, approach to modeling of structures of composite materials with delamination is proposed. Verification of this approach is carried out on the beam-samples DCB (Double Cantilever Beam) and ENF (End Notched Flexure), described in international standards ASTM. Good agreement is noted by comparing obtained results with data of foreign authors after numerical modeling of problem of quasistatic sample fracture of composite materials with delamination. Fatigue damages implementation algorithm at delamination front, using standard capabilities of program, was developed, because CAE-system ANSYS® allows simulating quasistatic growth of delamination. Algorithm bases on damage introducing at contact elements through applying of additional displacements at assumed delamination propagation area. Efficiency examination of proposed algorithm was conducted by the example fatigue fracture of double cantilever beam. Loading is carried out by two opposite forces at the end, which are applied to upper and lower layers of beam. These layers were produced of unidirectional material, reinforced by fibers, which was oriented along the beam axis. Initial delamination length equals to distance from the loading point to the defect front. Obtained results are in good agreement with the data of other authors. Basing on received data we can conclude about efficiencyand sufficient accuracy of proposed algorithm to modeling quasistatic and fatigued fracture of samples of composite materials with delamination.