Progressive Damage and Residual Strength of a Carbon Fibre Reinforced Metal Laminate

Abstract

An experimental study on the residual strength behaviour of a Carbon Fibre Reinforced Metal Laminate (FRML) was conducted. Mechanical tests were carried out to determine the laminate tensile property profiles and residual strength of notched coupon laminates. The effect of notch geometry was studied for both centre cracks and centre circular holes with notch sizes ranging from 10 to 40 mm. The reduction in residual strength for the saw-cut specimens was greater than that for the circular hole specimens. C-scan and optical microscopy associated with a chemical etching technique were used to investigate progressive damage and failure mechanisms in these laminates. Damage modes such as delamination, crack growth and fibre breakage were observed. Stable crack growth was seen in both the aluminium and composite layers for the saw-cut specimens, but no visible crack growth in the aluminium layers in the circular hole specimens was found although cracking in the composite layer occurred. It is concluded that delamination ahead of the notch tip is attributed to cracking of the composite layer. The average stress criterion developed for fibre reinforced composites was applied to correlate residual strength data and good agreement was obtained.