Investigation On The Impact Fracture Behaviors Of The Automotive Windshield Based On Cohesive Zone Models

Laminated glass is a sandwiched composite structure, which is normally fabricated by two soda-lime glass sheets and one one plastic interlayer, polyvinyl butyral(PVB), under high temperature and pressure. Though it is a simple composite structure, it is widely used in automotive and architectural industries. As one of the important component of an automobile, the investigation of impact fracture characteristics of the automotive windshield glass contributes to the pedestrian safety protection, traffic accident reconstruction and the design of the windshield glass. Currently, the impact fracture mechanism of laminated glass is investigated by means of theoretical analyses, experimental investigations and numerical simulations. In view of the advantages of numerical simulations, in this work, we focus on the development of cohesive zone-based finite element algorithms for the application of interest here.Firstly, because the glass material dissipates different fracture energies in normal and tangential fracture processes, we extend a two-dimensional cohesive zone model that is able to account for path-dependent behaviors to three dimensions to describe brittle fracture. A compact and efficient adjacency-based topological data structure termed TopS is utilized to store and manipulate mesh information during fracture.Afterwards, in view of the contact characteristics, we develop an efficient global contact search algorithm and a robust local contact search algorithm. The global contact search algorithm includes a regular search and an adaptive search. The regular search is performed by recourse to a linear contact algorithm named LC-Grid. The adaptive search algorithm based on LC-Grid is proposed to efficiently update new contacts during fracture. We consider two contact types,the node-face and edge-edge contacts, in the local contact algorithm. The proposed local contact algorithm is capable of eliminating the possible contact force jump which may arise during brittle fracture. Moreover, the contact judgments of these two contact types can be achieved by using a unified inside–outside approach. We validate the proposed contact algorithms via simple numerical examples. The cohesive model is coupled with the frictional contact algorithm to account for the unilateral and frictional sliding effects of cohesive elements under mixed mode loading.Finally, we propose a finite element laminated glass model, in which brick elements are adopted and an intrinsic cohesive formulation is employed to model the adhesion between glass and PVB. The nonlinear characteristic of PVB is described by using a Mooney-Rivlin constitutive model. We simulate the impact cracking behaviors of a laminated glass beam, and qualitatively validate the proposed model by comparing the simulation results with the experimental outcomes. We also numerically investigate the glass-ply cracking mechanism and the effects of the PVB ?lm and the adhesion on glass-ply cracking. We simulate the impact fracture behaviors of a laminated glass plate under drop-weight loading. The main fracture patterns including radial and circular cracks are captured. The simulation results compare well with the corresponding experimental outcomes in terms of the fracture patterns and the impact force, which demonstrates the capacity of the proposed method to simulate the impact fracture behaviors of laminated glass.Based on the proposed algorithms above, a finite element solver, FEP-Fracture, which is suitable for the impact fracture simulations of automotive laminated glass and other brittle materials is developed by using the Fortran 90/95 language.