一方向炭素繊維強化複合材料の高温における非主軸圧縮強度とそのモデル化

抄録

The off-axis compressive strength and its rate dependence of a unidirectional carbon/epoxy laminate are examined for various fiber orientations at high temperature. Static compression tests are carried out at two different strain rates of 0.1 and 10%/min for each fiber orientation. The fiber-orientation and strain-rate dependence of off-axis compressive strengths and associated failure modes are first discussed. The off-axis compressive strengths are compared with the off-axis tensile strengths at the same strain rates and test temperature, and differences between the ultimate off-axis strengths in tension and compression are quantified. Then, the Hoffman failure criterion that distinguishes between the off-axis strengths in tension and compression is tested for the accuracy of prediction of the different off-axis tensile and compressive strengths and the associated failure envelope at different strain rates. It is demonstrated that while the fiber orientation dependence of the off-axis tensile and compressive strengths are predicted with reasonable accuracy, the failure envelope associated with off-axis compression is poorly described using the Hoffman failure criterion. This observation suggests that consideration of the influence of the transverse compressive stress on the in-plane shear strength along fibers is essential for accurate prediction of failure envelope. Finally, a modified form of the Hoffman failure criterion that meets the requirement is proposed, and it is demonstrated to have an improved predictive capability compared with the original form.