炭素繊維強化複合材料の弾性率評価方法

概要

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A nonlinear behavior between tensile stress and tensile strain for carbon fiber and its composites is pointed out. In carbon fiber and its unidirectional composites, an increase of stiffness with increasing strain level is observed. Tensile elastic modulus is defined as a gradient of stress versus strain ; tangent modulus, secant modulus and chord modulus have been used. The value of the elastic modulus is varied related with method of evaluation and the range of applied strain. Therefore it is necessary to define the method of evaluation of the elastic modulus. In this paper, three kinds of method for the elastic modulus evaluation is exam-ined. As a results, initial tangent modulus is the best because of its universality. If evaluation of tangent modulus is difficult, chord modulus is desirable because of its smaller error with the evaluation. It is also required for the chord modulus that the strain range applied is declared.