A Review of Numerical Methods to Model Asphalt Concrete Delamination

Abstract: Delamination is a type of failure where a material fails due to the fracture in between its layers. For asphalt concrete, this problem affects the load transfer mechanism, and it is necessary to model the delamination of asphalt concrete interfaces. The numerical method is a suitable approach to model delamination. This method is capable of handling composite materials and geometric complexities. This review shows the different modes of delamination failures and different methods for numerical simulation of the delamination in layered structures. Fracture mechanics has been the dominant tool for studying interfacial delamination for many years. When other material non-linearities can be neglected, methods based on linear elastic fracture mechanics (LEFM) have been proven to be effective in predicting delamination growth. However, LEFM cannot be applied without an initial crack. After delamination onset, LEFM can be used to predict delamination growth. Techniques such as the virtual crack closure technique, the J-integral method, the virtual crack extension, and stiffness derivative have often been used to predict delamination growth. These techniques are used to calculate the components of the energy release rate. However, difficulties are also encountered when these techniques are implemented using finite element codes. The calculation of fracture parameters, e.g., stress intensity factors or energy release rates, requires nodal variables and topological information from the nodes ahead and behind the crack front. Such calculations can be done with some effort for a stationary crack but can be extremely difficult when progressive crack propagation is involved. Applying fracture mechanics techniques to an interfacial crack between dissimilar materials introduces additional challenges. Another method is the disturbed state concept (DSC). The DSC models interfacial delamination by describing material deformation as a combination of relatively intact (RI) and fully adjusted (FA) parts. The transition between these states, driven by microstructural changes, is quantified by a disturbance function, D, which ranges from 0 (fully RI) to 1 (fully FA). Cohesive zone (CZ) modeling is an emerging method capable of simulating crack initiation in addition to crack propagation. Therefore, a major advantage of cohesive zone theory over fracture mechanics theory is that CZ analysis does not require knowledge of starter crack size and geometry. CZ models have been used to simulate several types of interfaces, including integrated thin-film structures, adhesively bonded polymers, glass/elastomer, and on-chip interfaces. This review categorizes failure modes of delamination and critically evaluates various numerical methods to simulate delamination.