Application of the cohesive zone model to fracture and wear of heterogeneous solids
The cohesive zone model approach has been successfully accepted as a tool for fracture analysis. In this thesis, this approach is further investigated both experimentally and numerically to apply to studies of the fracture analysis of a carbon-carbon composite and a structural adhesive. Furthermore, a novel wear simulation approach by use of a fatigue cohesive zone model is established to studies of wear on a coating-substrate system and a metal matrix composite system. ^ A combined experimental-numerical investigation of crack growth in a carbon-carbon composite is studied. Crack growth experiments are performed on side notched DCB specimens. Cohesive zone laws are determined experimentally. Then, the cohesive zone law is characterized to separate into contributions from matrix fracture and fiber bridging respectively. Special focus of the numerical study is on the investigation on the discontinuous nature of crack growth by considering physically discrete fiber bundle bridging phenomena. Furthermore, the methodology is applied to investigate the crack growth in Hysol EA-9394 adhesive. Both 2D and 3D simulations are conducted by use of the cohesive zone law determined experimentally. 3D simulation result of strain fields obtains better agreement with the experimental measurements than the 2D simulation result. The transferability of the cohesive zone law approach has been investigated. The prediction of CTOA by use of cohesive zone methodology is also studied. ^ A wear simulation approach of finite element method based on a fatigue cohesive zone model is presented. The sliding wear of a coating-substrate system and a metal matrix composite system is analyzed. In the coating-substrate system, both models of coating delamination only and coating with defects are analyzed. Different failure modes are discovered with dependence of sliding amplitudes and loads. Wear rates are estimated and compared to the predictions from a classical wear law---Archard's law. In the metal matrix composite system, the delamination behavior is captured and the effect of loads, friction, material properties, particle locations and orientations are analyzed. ^
Thomas H. Siegmund, Purdue University.