DETERMINATION OF FIBER-RESIN INTERFACE STRENGTH IN FIBER-REINFORCED PLASTICS USING THE ACOUSTIC-EMISSION TECHNIQUE

The acoustic emission (AE) technique has been employed in a new way, t o deduce information regarding the level of adhesion and the strength of the bond between fibres and the matrix materials used in composite manufacture using a transverse sample based on fibre bundles. When uni directional composites of E-glass fibres/polyester and Kevlar-49 fibre s/polyester respectively were subjected to transverse tension, the AE events associated with fibre-matrix interfacial failure started and ev entually saturated at low strains in the materials containing Kevlar-4 9 when compared with those containing E-glass. This clearly indicates that E-glass adheres far better to polyester than does Kevlar-49 and, from stress measurements, the E-glass/polyester bond is stronger. Thes e results are compared and discussed with respect to those from single -fibre composite (SFC) tests which gave similar interfacial shear stre ngth values for the E-glass/polyester and Kevlar-49/polyester interfac es and which may be interpreted in terms of similar levels of adhesion . Further experimentation, with composites whose fibres were surface-t reated prior to composite manufacture, showed that the method is a sim ple and convenient means of monitoring adhesion and interfacial bond s trength in fibre-reinforced plastics. Acoustic emission has proved a u seful technique in casting new light on the quality (and reality) of s urface adhesion in composite material systems and has provided a new m ethod for measuring the strength of resin/fibre surface adhesion in te nsion.