Papers by Keyword: Bridging Toughening

Abstract: Based on the fiber bridging model and constant frictional interface stress, this paper derived the P-δ relation for the X-type fiber pulled out of cementitious matrix. By considering the random distributions of the bridging fibers and supposing that rupture of fiber never occurs, it derived the σ_B-δ relation of a single macro-crack, from which the fracture energy equation was deduced by integral. The derived toughening equations have continuous and explicit forms and are convenient for the approximate estimate of the fracture toughness of the composite. The fracture energy expression suggests that increasing fiber volume fraction, utilizing longer fibers or slender fibers and improving interface bonding are effective methods for improving the composite fracture toughness, while adopting fibers with higher elastic modulus is not a preferred suggestion. It is also found that when using X-type fibers to replace cylindrical fibers with same section area, one can obtain 3~8 times of fracture energy (corresponding leg length-width ratio of the X-type fiber cross section is 5~50).

Abstract: Based on the microstructure of fiber eutectics and transformation particles composite ceramic, the bridging stress of the fiber eutectic is determined. The bridging load that makes crack closure to reduce the stress concentration of crack tip is calculated. The energy dissipative value of the bridging load is obtained by considering the random orientation of the fiber eutectic. Finally, according to the relationship of the fracture toughness and energy dissipation, the bridging toughening mechanism is established. Analysis shows that the bridging toughening value is enhanced with the increasing of volume fraction and fracture strength of fiber eutectic, and enhanced with the decreasing of interface bonding strength and length-diameter ratio.