Strain fields around strain-concentrating features in fiber-reinforced oxide composites

Inelastic straining in the vicinity of strain-concentrating features in fiber-reinforced ceramic composites mitigates the high stresses that would otherwise be present and therefore alters the local conditions required to initiate fracture. The present study examines such effects through experimental measurements of strain fields around holes and notches in two oxide composites coupled with finite element simulations based on an inelastic constitutive model for the composite response. Computed strains fall within the bounds of experimental measurements for open-hole tension over most of the loading history. The results motivate a fracture criterion based on attainment of a critical normal strain over a characteristic area. The response of single edge-notched tensile specimens proves to be more challenging; because of the finite bending stiffness of the loading train, the boundary conditions on the test specimens evolve during loading, with bending playing an increasingly important role as the applied load is increased.