Determination of fracture parameters of laminated thermoplastic composite materials: a finite element approach

With the advent of new adhesives bonded joints are growing in use. These jo ints made up of different materials such as thermoset and thermoplastic-lam inated composite materials are prone to peel off at their interface leading to failure. In the present work an improved locking-free four-node finite element is developed. Developed locking-free element is validated for a can tilever beam under flexural loading condition. In fact, the element is obse rved to be free from parasitic shear leading to more accurate results. Furt her, the developed element is being applied for the fracture study of lamin ated composite materials for the first time. Double-cantilever beam (DCB) s pecimens of isotropy material and laminated composite materials are modelle d with locking free four-node plane strain elements to predict the fracture parameters. Crack growth along the interface of the joints are simulated b y sequential opening of paired nodes. Finite element analyses are carried o ut and strain energy release rates are computed. Using the developed elemen t accurate fracture parameters are obtained for isotropy and laminated comp osite DCB specimens. Simultaneously, experiments are conducted and strain e nergy release rates of the DCB specimens are determined. Computed strain en ergy release rates employing the developed element are in good agreement wi th those reported in literature and those obtained from the experiments. (C ) 2000 Elsevier Science Ltd. All rights reserved.