Browsing by Author "Peterson, William Matthew"

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Effect of fiber diameter on stress transfer and interfacial damage in fiber reinforced composites
(Montana State University - Bozeman, College of Engineering, 2011) Peterson, William Matthew; Chairperson, Graduate Committee: Christopher H. M. Jenkins
In this work, the effect of fiber diameter upon the strength, stiffness, and damage tolerance of a fiber-reinforced polymer composite laminate structure was investigated. Three cases were considered, in which the fiber diameters of 16, 8, and 4 microns were used. A fiber volume fraction of 32% was assumed in each model. Micromechanical, shear-lag, and progressive damage analyses were performed using finite element models of the structure, which was subjected to tensile loading in the fiber direction. Fiber-matrix load transfer efficiencies and the stress distributions near broken fibers within the composite structure were investigated and results compared for each fiber diameter. In addition, the effect of fiber diameter upon the initiation and evolution of fiber-matrix interfacial damage and debonding was studied using cohesive interface elements. For a specified volume fraction and load condition, as the fiber diameter was decreased the load transfer efficiency and effective stiffness of the broken fiber model increased. Also, as the fiber diameter was decreased, the initiation of damage at the fiber-matrix interface occurred at greater stresses and the subsequent growth of damage was less extensive. These results indicate that, for the same total mass, the performance and damage tolerance of composite materials may be enhanced simply by using smaller diameter fibers.
Selective Activation of Intrinsic Cohesive Elements.
(2014-12) Kyeongsik, W.; Peterson, William Matthew; Cairns, Douglas S.
In this paper, a selective activation strategy is studied in order to alleviate the issue of added compliance in the intrinsic cohesive zone model applied to arbitrary crack propagation. This strategy proceeds by first inserting cohesive elements between bulk elements and subsequently tying the duplicated nodes across the interface using controllable multi-point constraints before the analysis begins. Then, during the analysis, a part of the multi-point constraints are selectively released, thereby reactivating the corresponding cohesive elements and allowing cracks to initiate and propagate along the bulk element boundaries. The strategy is implemented in Abaqus/Standard using a user-defined multi-point constraint subroutine. Analysis results indicate that the strategy significantly alleviates the added compliance problem and reduces the computation time.