| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1989: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1988: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
Creep tests were carried out an aluminum composite reinforced with continuous alumina fibres at temperatures of 573 to 773 K to examine the mechanism of high temperature deformation and fracture of composite. 1. Creep curves in the low stress range showed only almost the primary or secondary stage without reaching the tertiary stage. The creep strain was consisted of an irreversible component, possibly due to the plastic deformation of matrix around the misaligned fibres, beside a reversible component due to the elastic and inelastic deformation of matrix and fibres. 2. In the high stress range, the creep deformation proceeded by the local fracture of fibres and the plastic deformation of matrix resulting in the fracture of specimen. The creep curves showed the primary, secondary and tertiary stages. 3. The critical stress which distinguished between the low and high stress ranges was a bout 500 MPa at 573 K and 450 MPa at 773 K. The critical stress was consistent with the threshold stress which was recognized in the stress dependence of minimum creep rate. The critical stress, or the threshold stress is taken as the minimum stress for the individual cracks of fibres to propagate extensively and to cause the fracture of whole specimen.
Furthermore, the effect of fibre orientation on high temperature tensile strength was examined by tensile testing the specimens which axis made the angles of Oﾟ,5ﾟ,10ﾟ,45ﾟ and 90ﾟ to fibre axis. The relation between fibre orientation and high temperature strength was well consistent with a criterion based on the maximum stress theory for fracture of composite, which was also supported by the observation of fracture surfaces.
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