Particle Strain Analysis of Epoxy-Based Composites Following Quasi-Static and Dynamic Compression
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We investigate localized strains in polymer-based composites subjected to varying strain-rates and strains. Research on composites is often focused on their bulk mechanical behavior. However, many material phenomena are influenced by their microstructure, such as the mixing and reaction mechanisms of constituents in structural energetic materials. Therefore, the response of composites at the mesoscale is of clear interest; especially as insight into the micro-deformation and damage, and interaction effects between the constituents at the local level will better inform our understanding of the bulk composite constitutive behavior. To more fully understand the composite mechanical behavior at the mesoscale, uniaxial compression experiments were conducted on epoxy reinforced with aluminum (20 or 40 vol%) and nickel (0 or 10 vol%) particles. Additionally, the particle size of aluminum was either 5 or 50 μm in diameter. Experiments were carried out at quasi-static and dynamic strain rates. Resulting microstructures were analyzed to measure the degree of particle strain and compared to the global material strains for different degrees of strain-rate, strain, and particle size and volume fraction. The aluminum particle strain increased with global strain and had a strong dependency on strain rate. Introducing stiffer nickel particles resulted in larger aluminum particle strains. The nickel particle strain was minimal (< 3%) and showed no dependency with strain rate. This research gives insight into the interactions of particle reinforced composite constituents and their deformation at the mesoscale which is important for understanding phenomena such as preignition mechanisms in structural energetic materials.
KeywordsAluminum Nickel Epoxy Polymer composite Particle strain Microstructure Dynamic
Bradley W. White would like to thank H. Keo Springer at LLNL for constructive comments and discussions in preparing this manuscript. The authors would also like to acknowledge the Air Force Office of Scientific Research (AFOSR) for their support through contract No. F-08630-03-C-0001. This work was partially performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-JRNL-670534.
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