δ25 Crack opening displacement parameter in cohesive zone models: experiments and simulations in asphalt concrete

Recent work with fracture characterization of asphalt concrete has shown that a cohesive zone model (CZM) provides insight into the fracture process of the materials. However, a current approach to estimate fracture energy, i.e., in terms of area of force versus crack mouth opening displacement (CMOD), for asphalt concrete overpredicts its magnitude. Therefore, the delta(25) parameter, which was inspired by the delta(5) concept of Schwalbe and co-workers, is proposed as an operational definition of a crack tip opening displacement (CTOD). The delta(25) measurement is incorporated into an experimental study of validation of its usefulness with asphalt concrete, and is utilized to estimate fracture energy. The work presented herein validates the delta(25) parameter for asphalt concrete, describes the experimental techniques for utilizing the delta(25) parameter, and presents three-dimensional (3D) CZM simulations with a specially tailored cohesive relation. The integration of the delta(25) parameter and new cohesive model has provided further insight into the fracture process of asphalt concrete with relatively good agreement between experimental results and numerical simulations.