Initiation and Evolution of Dynamic Failure Mechanisms in Woven Composite Systems

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Title: Initiation and Evolution of Dynamic Failure Mechanisms in Woven Composite Systems
Author: Baucom, Jared Newton
Advisors: Mohammed Zikry, Committee Chair
Harvey Charlton, Committee Member
Eric Klang, Committee Member
John Bailey, Committee Member
Yiping Qiu, Committee Member
Abstract: The unique reinforcement geometry of three-dimensional orthogonally woven fabric-reinforced composites offers the potential of improved penetration resistance, in comparison with other composite systems. However, there has been a lack of understanding of how dynamic energy dissipation and failure modes are affected by fiber orientation and distribution. The major objective of this investigation is to characterize damage progression in woven composites under transverse loading conditions at three distinct velocity regimes, ranging from 10 μm/s to 0.5 km/s. The investigated systems included two-dimensional plain woven laminates, three-dimensional orthogonally woven monoliths, and three-dimensional woven laminates. The three-dimensional structure has also been utilized with a matrix-cellularization technique to explore how porosity can be tailored for enhanced energy absorption. Quasi-static perforation experiments were conducted, where punch loads were recorded. Damage progression was monitored by backlit videography. The three-dimensional laminates required a higher punch force and absorbed more energy than the two-dimensional laminates and three-dimensional monoliths. Low-velocity impact damage progression was investigated with an instrumented drop-weight impactor. Measurements were obtained for impact force and energy dissipation for multiple strikes. The radial spread of damage was smallest for the two-dimensional laminates and largest for the three-dimensional woven composites, which also had the greatest resistance to penetration and dissipated the most total energy. High-velocity impact experiments were conducted to determine energy absorption and compare failure modes of two-dimensional and three-dimensional composite systems. Energy absorption was comparable for the various systems, but damage was more localized for the two-dimensional woven system. These results indicate that the three-dimensional laminates consistently had greater perforation resistance than the two-dimensional laminates and the three-dimensional monolithic composites. This is due to unique energy absorption mechanisms, which involve the crimped portion of z-tows in the three-dimensional composites. This implies that failure can be controlled by manipulation of the properties of the z-tows. Hence, three-dimensional architectures can provide both an inherent capability to dissipate energy over a large radial area and a greater perforation strength than comparable two-dimensional laminate and three-dimensional monolithic composites.
Date: 2002-08-21
Degree: PhD
Discipline: Mechanical Engineering

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