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SynopsisIn discontinuous fiber-reinforced composites, the critical fiber length plays an essential role in determining the mechanical properties. A method was devised to accurately determine the critical fiber length and the temperature dependence of the critical fiber length was studied for glass fiberepoxy and glass fiber-unsaturated polyester resin composites. If a continuous glass fiber is embedded in the matrix and the system is subjected to a tensile strain greater than the fiber ultimate tensile strain, the fiber breaks into many pieces. If the average length of these broken pieces (i) is measured, the critical fiber length (Zc) is expressed as 1, = 4/3i. The critical fiber length greatly increases with increasing temperature and the apparent shear strength a t the interface, calculated from the critical fiber length, decreases linearly with increasing temperature.

Since TFC high signal intensity was frequently detected in these asymptomatic wrists, MR imaging cannot reliably be used to detect clinically meaningful abnormalities.

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SynopsisEfforts were made to estimate the axial compressive strengths of carbon fibers from the fiber fragment lengths produced by subjecting to a strain greater than the fiber ultimate strain for PAN-based and pitch-based carbon fibers. The estimated compressive strength of carbon fibers decreases with increasing temperature in a temperature range from room temperature to 100OC. This decrease in compressive strength may be accounted for by a decrease in the radial compressing force. The real compressive strength, determined by extrapolating a linear relationship between the estimated compressive strength and the radial compressing force, is approximately 25-60% of tensile strength for PAN-based fibers, while it is approximately 10-35% for pitch-based fibers.