Kink crack problem in fiber reinforced composites.

摘要

This study is concerned in the problem of a kink crack in unidirectional fiber-reinforced composite materials. This work studies the singularity index, driving forces, stress intensity factors, and the strain energy release rates in the kink crack embedded in anisotropic materials (composite materials).; Specifically, the singularity index was studied analytically where a kink crack is embedded in an infinite anisotropic plate (the unidirectional laminate); the crack makes an arbitrary angle with the fibers and the plate is loaded in uniform tension. Which was formulated and solved exactly based on two-dimensional anisotropic elasticity. The numerical effort involves developing a finite element technique to verify the singularity index and obtain the driving forces, stress intensity factors, and the strain energy release rates.; In finite element a finite-width rectangular plate containing a kink crack is considered. To simulate an infinite plate, the length and width of the plate are made very large compared to the size of the kink crack.; The plate is loaded by a far-field displacement u_y = 1.0. The resulting stress field was highly concentrated near the crack tips.; Three composite materials where used to carry out the analysis, graphite/epoxy, glass/epoxy, and kevlar49/epoxy, with various fiber angles and kink angles.; The results showed that the singularity index and the driving forces (stress intensity factors, and the strain energy release rates) depend on the material properties, fiber angle, and kink angle.