カーボン長繊維強化型窒化ケイ素の衝撃三点曲げ試験(<特集>衝撃)

概要

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Bending strength of a continuous carbon fiber-reinforced silicon nitride was experimentally investigated at high rate of strain by a split Hopkinson pressure bar method. Ramped incident waves were applied to the specimen to obtain a smooth load-deflection curve without high frequency oscillations. Acoustic emission during impact deformation was successfully detected as well as quasi-static deformation and the evidence of micro-cracking in the relatively early stage of high velocity deformation was confirmed. The dependences of strength and fracture morphology on fiber orientation and specimen size were clarified and their rate dependences were also identified. Tensile strength was found to be almost independent of deformation rate, while shear strength along fiber direction was significantly increased with rise of strain rate. Fiber bridging over a fracture surface affected shear strength and provided a reasonable explanation of experimental results.
1996-07-15