Epitaxial growth of YBa2Cu3O7−δ films on oxidized silicon with yttria and zirconiabased buffer layers

Compression measurements were conducted on three explosive formulation binders, extruded Estane, plasticized Estane, and plasticized hydroxyl‐terminated polybutadiene, as a function of temperature and strain rate. The mechanical response of the Estane was found to exhibit the strongest dependency on strain rate and temperature and higher flow strength for similar test conditions of the three materials tested. Plasticized Estane was less sensitively dependent on strain rate and temperature, followed by the plasticized HTPB. The visco‐elastic recovery of all three binders is seen to dominate the mechanical behavior at temperatures above the glass transition temperature (Tg). There is a pronounced shift in the apparent Tg to higher temperatures as the strain rate is increased. Two distinct behaviors are observed in the binders below the Tg. At low strain rates, the binders exhibit a yield behavior, followed by a drop in the flow stress, which may or may not recover. At high strain rates, the load drop does not occur and the flow stresses either gradually increase, as in plasticized HTPB, or it levels out as seen in the Estane‐based binders. POLYM. ENG. SCI., 46:812–819, 2006. © 2006 Society of Plastics Engineers

The effect of sample thickness, strain rate, and temperature on the mechanical response of AdipreneLl00 is presented. The compressive stress-strain response of Adiprene-L100 was found to depend on both the applied strain rate; 0.001 I d I 7000 s-l, and the test temperature at high-rate; 77 I T I 298 K. Due to the slow, dispersive wave propagation in Adiprene-L1 00, thinner sample thicknesses are needed to assure uniform, uniaxial stress conditions within Hopkinson Bar samples; the optimal sample thickness being dependent on test temperature. Decreasing temperature from 298 to 77K at 3000 s-l was found to increase the maximum flow stress in Adiprene-L100 from 10 to -210 MPa.

A mathematical procedure is proposed for recovering from image analysis the three-dimensional (3-D) non-symmetric density distribution of fiber orientation and the average fiber length in short-fiber composites. The determination of fiber-orientation distribution and average fiber length is essential for assessing the mechanical and physical properties of a short-fiber composite. The average fiber length can be obtained from one micrograph, while the determination of 3-D fiber orientation requires micrographs from two orthogonal planar faces of a composite sample. In addition, a simple procedure is proposed to obtain the single-angle fiber-orientation distribution from one micrograph. This distribution is often needed for predicting the mechanical and physical properties in the direction normal to the plane of the photographed sample cross section. In processing the fiber-orientation density data obtained from a micrograph, a cumulative fiber-orientation density curve is used to derive the fiber-orientation function, which is simpler and more accurate than the histogram that has been commonly used. Previously reported procedures all assume symmetries in fiber-orientation distribution, and are therefore highly idealized. Without assuming any symmetry, the present procedure improves upon previous works.

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Abstract. Compression and tensile measurements were conducted on newly formulated (baseline) and lower molecular weight (virtually-aged) plastic-bonded explosive PBX 9501. The PBX 9501 binder system is composed of nitroplasticized Estane 5703, TM a polyester polyurethane copolymer. The molecular weight of polyester urethanes can degrade with time as a function of hydrolysis, affecting the mechanical behavior of the polymer or a polymer composite material of high explosives, i.e. PBXs. The molecular weight of Estane 5703 TM was degraded by exposure to high temperature and humidity for different periods of time, and then formulated to produce "virtually-aged" PBX 9501 specimens. Quasi-static and dynamic compression tests were conducted on the baseline and virtuallyaged PBX 9501 as a function of temperature and strain rate. Quasi-static tensile tests were also conducted as a function of temperature and test rate. Rate and temperature dependence was exhibited during both compression and tensile loading. Results also show significant differences between the baseline and virtually-aged specimens for the dynamic compression tests at -15°C, and for the quasistatic compression tests at -15°C, 22°C, and 50°C.

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