Abstract
The virtual crack closure technique is a well-known finite element–based numerical method used to simulate fractures and it suits well to both of two-dimensional and three-dimensional interlaminar fracture analysis. In particular, strain energy release rate during a three-dimensional interlaminar fracture of laminated composite materials can successfully be computed using the virtual crack closure technique. However, the element size of a numerical model is an important concern for the success of the computation. The virtual crack closure technique analysis with a finer mesh converges the numerical results to experimental ones although such a model may need excessive modeling and computing times. Since, the finer element size through a crack path causes oscillation of the stresses at the free ends of the model, the plies in the delaminated zone may overlap. To eliminate this problem, the element size for the virtual crack closure technique should be adjusted to ascertain converged yet not oscillating results with an admissible processing time. In this study, mesh size sensitivity of the virtual crack closure technique is widely investigated for mode I and mode II interlaminar fracture analyses of laminated composite material models by considering experimental force and displacement responses of the specimens. Optimum sizes of the finite elements are determined in terms of the force, the displacement, and the strain energy release rate distribution along the width of the model.
Highlights
Delamination is the most important life-limiting damage type in laminated composite materials[1,2] because of the difference between the mechanical properties of reinforced plies and the resin rich interfaces
Force reactions of the double cantilever beam (DCB) arms to the displacement in mode I fracture are shown in Figure 4 for different element sizes
Due to the nature of virtual crack closure technique (VCCT), when the concentrated strain energy reaches a critical value on the nodes, the length of the DCB arm increases with the separation of the coincident nodes
Summary
Delamination is the most important life-limiting damage type in laminated composite materials[1,2] because of the difference between the mechanical properties of reinforced plies and the resin rich interfaces. Presence of the continuous reinforcements in plies hinders the scatter of delamination crack into subsequent interfaces and the delamination propagates in a certain path.[3,4] virtual crack closure technique (VCCT) is an appropriate numerical method to model the interface delamination problems in the laminated composite materials,[5,6] since the method assumes that the crack grows in a predefined path. VCCT was first introduced by Rybicki and Kanninen[7] and have been used by researchers since to identify the interlaminar fracture characteristics of composite materials.[6,7,8,9,10,11]
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