The constitutive behavior of composite laminates under general conditions is very complex, as several physical mechanisms can occur and interact with each other. In this thesis a material model is developed to describe the nonlinear response of laminates without fibers aligned in load direction. It is shown, that despite the plastic behavior of the epoxy resin the consideration of fiber rotation and inter-fiber damage is essential for large deformations. A test series of angle-ply tension tests with various off-axis angles and ply thicknesses has been conducted to provide an experimental basis. The tests have shown that the ply thickness only influences inter-fiber damage and the laminate strength but not plastic yielding. For further validation unidirectional off-axis compression tests from literature have been simulated. The implemented material model shows excellent correlation for all investigated specimens. The second part of this work addresses the numerical efficient representation of ultimate laminate failure.
Ulrich Mandel
fiber reinforced plastics nonlinear material behaviour angle-ply laminates