3-D Analysis and Verification of Fracture Growth Mechanisms in Fiber-Reinforced Ceramic Composites.

摘要

This final report documents a 3-D computational and experimental investigation into the mechanics of toughening a brittle matrix by incorporating long brittle fibers. Computationally, small scale failure, mechanisms ahead of a crack are explicitly modeled and merged with a continuum representation of the far field outside the process zone. Particular attention is given to the interfacial decohesion and frictional slipping near the tip of a matrix crack which is impinging upon an inclusion. The surface integral and finite element (SIFEH) method, which employs the principle of superposition to combine the best features of two powerful numerical techniques. provides an extremely flexible and efficient computational platform for modeling linear elastic fractures near material inhomogeneities. Applications to general 3-D fracture growth in multimaterial media demonstrate the capabilities of the computational technique and are also described. The computational simulation is being guided by laboratory experiments. Crack growth observations made on a model (microstructure) structure comprising a glass rod embedded in a cement matrix show the toughening mechanisms of crack pinning and crack bridging in operation. In a second experiment, interfacial slip evolution was modeled experimentally for planar bimaterial interfaces. This combined experimental and numerical program is providing insight into optimal combinations of the key parameters (e.g. residual stresses at interface, friction coefficient, strength of fibers) to maximize toughness. Fracture Mechanics; Fiber-Reinforced Composites; Ceramic Composite Materials; Surface-Integral Method.