Global-local analysis of composite structures using finite element method.

摘要

This work involves the application of global-local finite element techniques to two multi-material, large-degree-of-freedom structures: a superconducting outsert of a 45-Tesla magnet and a metal matrix composite laminate. The design of the magnet outsert is significantly improved by applying a global-local finite element technique adapted for multi-material systems. The design improvement is achieved by the iterative application of the technique to the magnet, with the aim of reducing the wall-thickness of the conduit in the conductor of the magnet. Two such cases were considered and significant reductions in mass were achieved as a result. Thickening the corners of the conduit resulted in a mass reduction of the outsert by 29% and changing the aspect ratio reduced the outsert mass by 25%.; In fiber-reinforced metal matrix composites (MMCs), damage mechanisms at the micro-mechanical level such as fiber fracture, interfacial debonding and matrix plasticity were explicitly modeled to study their initiation, evolution and interaction. A Monte-Carlo procedure incorporating fiber fracture and debonding mechanisms was implemented to simulate the behavior of a {dollar}0sp0{dollar} lamina under a tensile load. It was seen that local load sharing occurred upon fiber fracture, leading to a cluster of fractures in its vicinity. On the basis of a three-fiber model used in this work, it is inferred that increasing fiber volume fraction leads to more correlated cracking of fibers in the {dollar}0sp0{dollar} lamina. It was shown that local load sharing mechanism is active in the failure of an MMC lamina. The damage mechanisms in the {dollar}0sp0, 45sp0{dollar} and {dollar}90sp0{dollar} laminae were modeled and quantified in the form of a damage tensor and applied to model the behavior of 'global' model of a composite laminate.