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 joints made up of different materials such as thermoset and thermoplastic-laminated 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 cantilever beam under flexural loading condition. In fact, the element is observed to be free from parasitic shear leading to more accurate results. Further, the developed element is being applied for the fracture study of laminated composite materials for the first time. Double-cantilever beam (DCB) specimens of isotropy material and laminated composite materials are modelled with locking free four-node plane strain elements to predict the fracture parameters. Crack growth along the interface of the joints are simulated by sequential opening of paired nodes. Finite element analyses are carried out and strain energy release rates are computed. Using the developed element accurate fracture parameters are obtained for isotropy and laminated composite DCB specimens. Simultaneously, experiments are conducted and strain energy release rates of the DCB specimens are determined. Computed strain energy release rates employing the developed element are in good agreement with those reported in literature and those obtained from the experiments.