Zhenjun Yang

From micro to macro: Simulating crack propagation in carbon fibre composites

Abstract In this paper, the most popular multi-scale modelling methods are reviewed and discussed to some detailed extent. Particular emphasis is made on current challenges when modelling the scale transfer by using fine-scale simulations. Most existing modelling methods in literature either pose limitations to the capability of modelling the fully nonlinear range, such as when modelling crack growth, or they are using simplified repetitive microstructural arrangements. Coupling methods are further discussed, followed by an exact crack growth modelling preview in carbon fibre composites. Crack simulations were carried out in two dimensions on image-based models obtained from real micrographs. The crack growth was modelled using the cohesive interface crack model. It is shown that the difference in fibre volume fractions contained in the computed meso-scale window has an important consequence on the final elastic moduli, ultimate strengths and softening fracture energies. The latter were mainly influenced by the tortuosity of the crack paths.

Seismic Performance of Multistorey Masonry Structure with Openings Repaired with CFRP Grid

FRP composites have been used for strengthening RC and masonry structures for decades. However, the researches on repairing multistorey masonry structures using FRP grids were relative less. In the present paper, an experimental study on the seismic performance of multistorey masonry structure with openings repaired with CFRP grid is introduced. Specifically, a 1/3-scale three-floor masonry wall with window openings was tested under quasistatic action to simulate the seismic damages. The damaged masonry wall was then repaired by externally bonding CFRP grids to the areas where the cracks intensively occurred. The repaired masonry wall was retested under the same loading to investigate the seismic resistance and assess the recovery attributed from the CFRP grid repairing. The findings of this study showed that CFRP grid repairing could effectively postpone or even prevent the occurrence and development of cracking. The seismic resistance of the masonry, including shear capacity, energy dissipation capacity, deformability, stiffness degradation, and ductility, was restored. The application of CFRP grid may shift the failure mechanism of the multistorey masonry wall. The recommendation of repair scheme for the similar structures was also proposed in accordance with the findings of the present work.