Defense Tech Briefs - High-Strain-Rate Tests of Epoxy/Aluminum-Powder Composites

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High-Strain-Rate Tests of Epoxy/Aluminum-Powder Composites

Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio

Dec 01 2007

Page 1 of 2

It is important to understand how composites behave under complex, changing loads.

Initial tests have been performed in a continuing experimental study to determine selected mechanical properties, at high strain rates, of an epoxy and of composite materials consisting of the epoxy filled with aluminum powders. These composites are examples of the large variety of polymer-matrix/particlefilling composites in general, which are widely used in military and civilian applications. The properties of such composites can be tailored for specific applications through appropriate choices of constituent materials, the proportions of the constituent materials, and the sizes of the particles. Especially in aerospace structural applications, the composites are exposed to complex, temporally varying loads. Therefore, the mechanical properties of such composites’ high strain rates are of increasing importance.

$These Stress-vs.-Strain Data and associated fracture-surface micrographs were obtained in flexural tests of specimens of two composites containing differently sized particles.$

These Stress-vs.-Strain Data and associated fracture-surface micrographs were obtained in flexural tests of specimens of two composites containing differently sized particles.

The epoxy used in this study is made from a bisphenol- A resin, known by the trade name “Epon 826,” with a diethanolamine hardener. Two composites were examined in the initial tests. In both composites, the proportion of aluminum powder was 46 volume percent (equivalently, 65 weight percent). The powders in the two composites are known by the trade names “Valimet H2”and “Valimet H3.” The particle sizes, specific surface areas, and mass densities of the particles were determined by use of a light-scattering technique, a static volumetric technique, and pycnometry, respectively. The results of these determinations were the following: The H2 powder was found to have a specific surface area of 1.522 ±0.093 m²/g, a particle size of 3.479 ±0.042 μm, and a mass density of 2.720 ±0.012 g/cm²; the H3 powder was found to have a specific surface area of 1.145 ±0.032 m²/g, a particle size of 5.425 ±0.078 μm, and a mass density of 2.688 ±0.009 g/cm².

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