Thermal joining of carbon fibre reinforced PEEK laminates

Abstract

The heated press technique was used to thermally join carbon fibre reinforced PEEK. The resulting lap-shear specimens enabled the effect of varying certain geometric and processing parameters to be studied in detail. It was shown that the measured joint strength is dependent upon both the geometry of the lap-shear test specimen and the thickness of the joint itself. Tests at elevated temperatures indicated that these welded joints offer excellent strengths even when tested above the glass transition temperature of the PEEK matrix. It was also shown that the joint strength depends strongly upon the orientation of the outermost fibres in the composite adherends. Joints in which the surface fibres are oriented at 90° to the applied stress were shown to be 40% weaker than those in which the fibres are parallel to the loading direction. A series of tests were also undertaken in order to examine the possibility of joining this fibre reinforced thermoplastic at temperatures below the recommended processing temperature of 380°C. Here, it is shown that by employing a sufficiently long contact time, it is possible to obtain very high joint strengths at temperatures just above the melting temperature of the PEEK matrix.