|Budget Amount *help
¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 1995 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1994 : ¥800,000 (Direct Cost : ¥800,000)
If a sufficiently long fiber is embedded in the neighborhood of the surface of a rectangular beam, and the system is subjected to a tensile of compressive strain greater than the fibes's ultimate strain according to the bending method, the fiber eventually breaks into many pieces. By measuring the lengths of broken pieces and estimating the mean tensile strength from the length just before the final fragment length in tension, attempts were made to estimate the fiber axial compressive strength of carbon fibers. Furthermore, the relationships between the compressive strength and fiber diameter, surface-, sizing treatments, and microstructures were investigated.
The estimated compressive strength of fibers decreases with increasing temperature. This decrease in compressive strength may be accounted for by a decrease in the radial compressive force owing to a decrease in the residual thermal stress and a decrease in Young's modulus of the resin matrix.
There is a linear relationship between the estimated compressive strength and radial compressive force in a temperature range from room temperature to 60ﾟC.The real compressive strength of the fibers, determined by extrapolating this straight line until the radial compressive force is zero, increases with increasing degree of orientation or face spacing of the crystal. In addition, it increases with decreasing crystal size. Furthermore, it increases with decreasing fiber diameter. Also, it increases with increasing the shear yied strength at the fiber-matrix interphase, i.e., by surface- and size-treatments.