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Filament wound/ CVD (Chemical Vapor Deposition) carbon-carbon composites have received considerable attention and application within the past few years because of their desirable characteristics such as high heat of ablation, thermal shock resistance, high strength at elevated temperatures, and chemical inertness. However, poor mechanical properties in the transverse direction have hampered the total effectiveness of these composites in some applications and a study of the effects of porosity on transverse tensile strength of filament wound/ CVD carbon-carbon composites has been conducted. Two types of filament wound/ CVD carbon-carbon composites were studied. A standard filament wound/ CVD carbon composite, and a composite similar to the standard processed composite; but with short chopped carbon fibers sprayed on the substrate during the winding process. Transverse tensile strength, volume fraction of open cell porosity, pore geometry, size, and orientation were determined. A linear relationship was observed for the logarithm of transverse tensile strength as a function of volume fraction porosity. However, a considerable difference in the slopes of the lines for sprayed and unsprayed materials was observed, indicating the effect of a parameter other than volume fraction porosity. This additional parameter is pore size distribution. The transverse tensile strength of filament wound/ CVD carbon-carbon composites is drastically reduced by increasing volume fraction porosity. In addition, parameters such as pore size distribution, orientation, and geometry are also important, and should be considered when studying porosity effects. The theoretical model prepared by Brown et al [6] for predicting the strength of polycrystalline materials as a function of porosity (size, geometry and orientation) appears reliable for predicting transverse tensile strength of filament wound carbon-carbon composites.

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The alloy V-15Cr-5Ti was cyclotron-implanted with 80 appro He and subsequently irradiated in the Experimental Breeder Reactor (EBR-II) to 30 dpa. The same alloy was also irradiated in the 10, 20, and 30% cold-worked conditions. Irradiation temperatures ranged from 400 to 700°C. No significant effects of helium on mechanical properties were found in this temperature range although the neutron irradiation shifted the temperature of transition from cleavage to ductile fracture to about 625°C. Ten percent cold work was found to have a beneficial effect in reducing the tendency for cleavage fracture following irradiation, but high levels (20%) were observed to reduce ductility. Still higher levels (30%) improved ductility by inducing recovery during the elevated-temperature irradiation. Swelling was found to be negligible, but precipitates -titanium oxides or carbonitrides -contained substantial cavities.

The residual resistivity increase rate as a function of induced resistivity for fast neutron irradiated Al, Cu, Ag, Au, Pt, Fe, Ni, Co and Mo has been studied. Except for Fe the resistivity increase rate as a function of irradiation induced resistivity is non‐linear. The data is best explained with the expression of Balarin and Hauser. Saturation values of the resistivity and defect concentrations plus static and dynamic recombination volumes have been calculated; they differ from those obtained by irradiation in a reactor spectrum. Recombination volumes are very small for the b.c.c. metals Fe and Mo.