FRPの機械的継手における疲労寿命と疲労破壊

概要

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The mechanically fastened joints or rivettings in composite structures are becoming increasingly applicable for fabricational simplicity and structural efficiency. The unskillful design of joints often causes reduction of the bearing capacity of composite structure, even if each member in the structure has sufficient strength and stiffness. Therefore, special attention must be given to the design of the mechanical fasteners. In this paper, we discuss the fatigue life and the failure modes for mechanically fastened joint in glass fiber reinforced plastics. The pulsating tensile stress is applied on the joints. The relationship between the displacement of the joint and the test time are observed. Two kinds of failure mode are obtained. The point at which a rapid increase of deformation awakes in the displacement-time curve is estimated as the fatigue life. In the case of bearing failure, it is clear that the damage mechanism of specimen in the fatigue test is different from that in the static tensile test. Furthermore, it is obtained that the fatigue life is independent of the geometry of specimen for the hearing failure. In the statistical approach, it is found that the gradient of the straight lines in the S-N diagram is different for each failure modes and the gradient of the line beyond the bearing failure is larger than that of the another line.