Delamination Simulation Of Laminated Plates Based On A Progressive Damage Model

Fiber reinforced laminated plates possess high specific modulus and high specific strength in the reinforcement direction and they are widely used in aerospace etc. However, the transverse strength of laminated plates is very weak, especially at the adhesive layers which are resin rich zones at the interlaminar interfaces. As a result, laminated plates will suffer damages, such as matrix cracking, delamination,matrix shearing and fiber fracture, when they are under the action of low-velocity transverse impact. Among these impact damages, delamination is the most dangerous one. Although researchers have proposed a new interface element (SOLSH190 element) which can predict the mechanical behavior and failure mechanism of interfacial layers more accurately in the delamination simulation of composite laminated plates, the progressive damage of adhesive layers affect the delamination is not considered. This thesis will analyze the delamination simulation of laminated plates based on a progressive damage model.With a delamination analysis of the laminated, we use the stress-strain relationship of adhesive layers to describe the interface layer deformation and damage, the damage of the materials is occurred with the plastic strains. When the damage reaches a certain level, the adhesive layers is failed, the delamination of laminated plates are occurred. According to the Lemaitre damage model, We can use a free energy that considers the internal variables damage, we can not only induce a continuous and smooth but also a progressive damage model.Two methods of numerical integrations, that is, the average method and the Gauss point method, are used for the caculation of the damage evolution in a finite element. The birth and death function of solid-shell interface element is adopted to simulate the propagation of delamination of end notched flexure model and mixed mode bending model. The numerical results of two method of calculating damage parameters are more consistent with the experimental results than the results of one step degradation method, which the Gauss point method is more accurately than the average method.We can consider the low velocity impact problem as a quasi-static problem. We use the largest impact force with the form of quasi-static concentrated force acting at the centre of the plate. There are three typical laminate structure examples, combined Gauss point method is more closer to the experimental results than the one step degradation method.The study of this thesis indicates that the damage model based on continuum damage mechanics combined with two method of numerical integrations can simulate the damage process of progressive degradation, which the Gauss point method is more reasonable in calculating the element damage parameter.