Crack branching in composite materials

• Main Author: Goh, Wei Zhen.
• Other Authors: Xiao Zhongmin
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Materials::Composite materials
• Online Access: http://hdl.handle.net/10356/17107
• Institution: Nanyang Technological University

This project covers the parametric study of the stress intensity factors of a horizontal crack branching into two directions at the same angle and same distance, when the propagation of the crack is retarded by an inclusion. The analysis is performed with the finite element software, ANSYS/ MULTIPHYSICS. Different crack geometries are compared and studied by applying small increments to the particular parameters to be investigated. It is observed that the stress intensity of varying branching angles reaches a maximum at about an angle of 20 degrees, while stress intensities rapidly decreases as the branching angle becomes larger than 20 degrees. The stress intensity is also greatly influenced by the geometry of the ratio of the branched crack length compared to its total length. Given the same horizontal crack length, a crack with larger branch crack length is better able to reduce the stress intensity than its shorter counterpart. The size of the inclusion in this study is discovered to have a linear relationship with the stress intensity. In general, inclusions with Young’s modulus smaller than the matrix’s will cause the stress to increase, while inclusions of strong strength are more effective in reducing the stress intensity at the crack tip.