Paper number 972

EFFECTS OF SPECIMEN ORIENTATION ON THE FATIGUE CRACK GROWTH RESISTANCE OF CROSS-PLY TI-6AL-4V/SCS-6 METAL-MATRIX COMPOSITES

A. Yasmin, T. J. A. Doel and P. Bowen

School of Metallurgy and Materials/IRC in Materials for High Performance Applications
The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK

Summary The fatigue crack growth resistance of cross-ply [0/90]2s laminate of Ti-6Al-4V reinforced with continuous SCS-6 fibres has been investigated at room temperature for three different mode-I crack growth directions relative to the axis of the fibres in the [0/90]2s laminate: 30, 45, and 60. The tests were conducted under three point bending at initial applied stress intensity range ((Kini) from 8 to 14 MPa. When tested with the mode-I crack growth direction at 30 and 60 to the fibre axis, a CA/CF (Crack Arrest/Catastrophic Failure) transition of 10-12 MPa was found, whereas when the mode-I crack growth direction was at 45 to the fibre axis the transition was 8-10 MPa. Unlike crack propagation in unidirectional composites for crack growth perpendicular to the fibre axis, and for crack growth perpendicular (and parallel) to the fibre axis in [90/0]2s and [0/90]2s cross-ply laminates, the fatigue crack is found to grow at an angle to the mode-I direction. For the specimens where mode-I directions are at 60 and 30 to the fibre axis, single dominant fatigue cracks were found to grow. However in the case of 45, multiple cracks have been found to grow under some of the conditions used.
Keywords effects of crack orientation, cross-ply, fatigue crack growth, fibre orientation, silicon carbide fibre, fibre bridging, crack arrest and catastrophic failure.

Theme : Metal Matrix Composites ; Characterisation and Modelling

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