Papers by Keyword: Bridging Stress

Abstract: This paper describes the effect of fiber diameter of fiber reinforced concrete (FRC) under fatigue behavior and its design method. Some researchers showed that the fatigue behavior of FRC is mainly governed by the bridging stress degradation, but little information is still available so far. We conducted fatigue tensile experiments of the FRC under constant strain amplitude first and the degradation of bridging stress was measured experimentally. Then, the micromechanics-based theoretical model is also developed, and the model is verified by the test results. The model accounts for the loss of fatigue ruptured fibers of which fatigue rupture is based on S-N relationships. The parametric study from the micromechanics-based theoretical model indicates that the best fiber diameter varies according to the number of cycles and strain level applied to the FRC specimen. The result suggests that we need to design FRC with considering the application and its loading conditions to utilize the capacity of FRC.

Abstract: This paper describes the optimal design of ductile fiber reinforced cementitious composite (DFRCC) under fatigue loading. First of all, fatigue tensile experiments of the DFRCC under constant strain amplitude were conducted, and the degradation of bridging stress was measured. The test results were employed to verify the micromechanics-based theoretical model developed in this research. The model accounts for the loss of fatigue ruptured fibers of which fatigue rupture is based on S-N relationships. According to the parametric study from the theoretical model, we found that the optimal choice of design variables, such as fiber length, is varied according to the maximum strain level and the number of cyclic loading. Therefore, it is required to design DFRCC optimally under given loading conditions to make the most of its excellent material properties and the developed model enables such a design.

Abstract: after reasonably analyzing characteristics of flexible fiber reinforcement fragile material, the mechanical model of individual fiber is established while being pulled out from asphalt; the spherical coordinates is adopted to establish the calculation model for short fiber bridging stress evenly distributed in space to calculate the value of bridging stress generated by short fibers while asphalt is breaking; the fiber asphalt sample in big size is adopted to perform low temperature tensile failure test to practically measure bridging stress of short fiber; fit the calculated value and measured value of bridging stress by adjusting parameters in the calculation model to check the rationality of fiber bridging stress in calculation method and model.

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.