Damage and Fracture of Composite Materials and Structures
Ha, Y. Hallett, S.
Halpin, J. Hu, W. Jiang, W. Jose, S.
Kazemahvazi, S. Kortschot, M. I: Measurements of damage and strength. II: A damaged-based notched strength model. Kilic, B.
Lee, D. Pineda, E. Ravi, S. Silling, S. Tsai, J.
Xu, J. Yang, W. Related work to study their fracture behaviour has been limited. This thesis includes an experimental and analytical investigation of fracture characteristics of composite materials. The post-peak response of notched specimens subjected to uniaxial cyclic loading is established to evaluate the fracture energy associated with progressive matrix damage and subsequent crack growth.
Fracture and Damage of Composites
A total of 75 uniaxial tension specimens were tested. The experimental work consisted of first testing several un-notched specimens with different thickness number of layers to determine the initial and secondary elastic modulus as well as the tensile strength. The specimens used in this research were prepared using the vacuum bagging technique, with a chosen number of fiber glass cloth layers and fiber orientation. The load versus crack opening displacement as well as crack length, fracture toughness and fracture energy versus number of loading cycles are produced for different specimens.
Based on the experimental results, concepts of fracture mechanics are applied to evaluate stiffness degradation, fracture toughness and fracture energy evolution associated with crack growth. In addition, a linear elastic fracture mechanics approach combined with continuum damage representation is used to predict the response of specimens peak load and crack opening displacement. This effort has also generated a new crack band model for computational purposes.
A new formula is derived to compute delamination and interlaminar buckling loads using the finite element method. By matching the analytical near crack tip displacement field with the finite element approximation, the crack-axial stress magnitude is established, and therefore an accurate assessment of the buckling load responsible for delamination of composites is accurately evaluated.
A comprehensive derivation of the fracture inelastic zone size and shape in anisotropic solids is presented. An adaptation of Hill's failure criterion is used to derive the shape of the inelastic zone.