長繊維強化金属基複合材料の疲労き裂における繊維架橋応力の評価(S06-1 薄膜・微小郎域の応力評価,S06 放射光による応力測定と残留応力評価)

概要

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Long fiber reinforced metal matrix composites have several advantages in structural applications such as high specific stiffness and strength at high temperature. For the fatigue crack propagation in the composite, the reinforced fibers act as bridges between crack wakes. Since the driving force of the fatigue cracks is reduced by the bridging effect, evaluation of the bridging force in the reinforced fibers is very important for design and life estimation. In the present paper, titanium alloys reinforced with SiC_f were fatigued under four-point bending. The residual stress and loading stress in each fiber were measured by the X-ray diffraction method. The loading and residual stresses in the fiber can be successfully measured by the X-ray method. The stress in the first fiber decreases linearly with the distance from the crack wake. The frictional stress between the matrix and the fiber could be determined by the experimental results. The bridging stress could be also determined by the X-ray method. The crack shielding effect by the fibers could be evaluated. The stress intensity factor range was corrected by using the bridging stress. When compared at the same stress intensity factor range, the crack propagation rate of the composite is close to that of monolithic titanium alloys.
2004-09-04