カーボン長繊維強化型窒化ケイ素の三点曲げ強度

概要

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The strength of continuous carbon fiber reinforced Si_3N_4 composite was investigated in a three-point bending test at low deflection velocity. On the load(P)-deflection(δ)curve inelastic behavior was observed together with AE(acoustic emission) events which may probably correspond to delamination at the interface of fiber and matrix, and/or cracking in matrix. The bending strength and the fracture morphology depend greatly on the H/L ratio where H is the height of specimen and L is the span, since the interlaminar shear strength of the material is unexpectedly lower than the tensile strength in the fiber direction. Consequently, the tensile strength can be adequately evaluated by reducing the specimen height to prevent shearing fracture. It is also found that the shear strength in the fiber direction is much lower on the perpendicular plane than on the parallel plane to the hot pressing. The fabrication process induced microcracking which degraded the elastic properties of the material. Significant load reduction and associated AE events were observed in the relaxation test and strong time-dependence of microcracking was revealed.
1995-08-15