Study on Damage Mechanism of Fiber Concrete with Initial Pores

Currently, fiber-reinforced concrete, as a building material, is widely used in highway bridges and tunnel linings, and it has become a global research hotspot, with indoor tests, numerical simulations, performance studies, and application scenarios surrounding it. Many researchers have conducted experiments and analyses on the damage patterns of fiber-reinforced concrete under different conditions. However, there is relatively little research on the mechanical properties of fiber-reinforced concrete that already contains initial damage. This article establishes a micro-model composed of aggregates, mortar, and interface layers using MATLAB. It introduces the CDP (Concrete Damage Plasticity) constitutive equation for fiber-reinforced concrete and uses the least squares method to fit and validate the equation. After model validation, uniaxial compression tests are conducted on models with different initial porosities using the ABAQUS (2023) software, resulting in changes in crack damage, peak stress, and elastic modulus mechanical properties. The conclusions are as follows: The improved characteristic structure curve using the least squares method fits the experimental results well, and the rationality of the algorithm was verified by comparing it with physical tests. As the porosity increased from 2% to 8%, the peak stress decreased from 98.6% to 70.5% compared to non-porous fiber concrete with a significant rate of decrease of about 30%. After considering the strain rate, the peak stress increased slowly with increasing strain rate, but the elastic modulus increased at a significant rate, with a 1.26 times higher elastic modulus at a strain rate of 10⁰ than at a strain rate of 10^-2. This result provides a certain theoretical basis for the mechanical properties and damage modes of fiber-containing concrete in practical engineering.