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In this work, a topology optimization algorithm is developed and implemented to get an optimum composite patch shape. Typically, the design process consists of an iterative analysis, where the best solution is obtained from a comparative study. In this way, we propose a topology optimization algorithm applied to obtain the optimum composite patch shape. The algorithm is implemented in MatLab, and uses the commercial finite element code Abaqus/Standard. A numerical example is analysed to show the capability of the proposed method. The obtained results are compared with numerical results reported by other researchers, revealing the potential of the developed algorithm. [ABSTRACT FROM AUTHOR]

In this work, the performances of circular single- and double-sided composite patch repairs are compared by computing the maximum stress intensity factor of a repaired surface crack. The three-dimensional finite-element method is used to calculate the stress intensity factor along the crack. The effects of the crack depth, composite patch thickness and patch material on the stress intensity factor variation are highlighted. The obtained results show that the selection of single- or double-sided patches depends on both the crack depth and patch thickness. [ABSTRACT FROM AUTHOR]

The fracture behavior of polymeric materials has been widely studied in recent years, both experimentally and numerically. Different numerical approaches have been considered in the study of crack propagation processes, from continuum-based numerical formulations to discrete models, many of the latter being limited in the selection of the Poisson's coefficient of the considered material. In this work, we present a numerical and experimental analysis of the crack propagation process of polymethylmethacrylate beams with central and eccentric notches subjected to quasi-static three-point bending tests. The developed discrete numerical model consists of a regular triangular lattice model based on axial and normal interaction springs, accounting for nearest-neighbor interactions. The proposed model allows solving the above mentioned limitation in the selection of Poisson's coefficient, incorporating a fracture criterion defined by a bilinear law with softening that includes the fracture energy in the formulation and allows considering a progressive damage. One of the main objectives of this work is to show the capacity of this lattice to simulate quasi-static fracture problems. The obtained results show that the proposed lattice model is capable of providing results close to the experimental ones in terms of crack pattern, peak load and initial stiffening. [ABSTRACT FROM AUTHOR]