PAN系炭素繊維の疲労強度特性

概要

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Load-controlled fatigue tests were carried out on PAN-based monofilament carbon fibers under cyclic tensile load conditions at a frequency of 10Hz.Fatigue strength data are obtained under pre-determined maximum load P_max with three different stress ratios of R(=P_mix/P_max)=0.1, 0.5 and 0.7.The maximum load P_max is not an appropriate parameter to evaluate the fatigue strength behavior because the cross-sectional area of monofilament carbon fiber is not constant and varies along the longitudinal direction.This fact results in a large scatter of fatigue lives when the data are plotted on P_max-N_f diagram.In order to evaluate the evaluate the fatigue strength behavior more precisely, the fatigue strength data must be plotted on S-N diagram by using the maximum tensile stress σ_max determined from the crosssectional area of the fracture surface.It is found that S-N properties of monofilament carbon fibers clearly show the fatigue behavior, depending on the stress ratio R.It is also found that the fatigue strength of monofilament carbon fiber is governed by two parameters such as the maximum stress σ_max and the stress amplitude σ_a, and that the combined stress parameter σ_max~(1-α)×σ_a~α is useful to describe the fatigue strength behaviors of the different stress ratios.
社団法人日本材料学会の論文
2000-04-15