THE INTERFACIAL PROPERTIES OF ARAMID EPOXY MODEL COMPOSITES/

Many attempts have been made to measure, evaluate and improve the leve l of interfacial adhesion in aramid/epoxy composites. Different surfac e treatments have been developed in order to promote chemical bonding between the fibre and the matrix but it is found that most of the surf ace treatments developed have shown little or no improvement in the le vel of interfacial adhesion. The interfacial properties of a model com posite are often determined by measuring the interfacial shear strengt h using micromechanical test methods that employ different loading con figurations. However, the values of interfacial shear strength determi ned using different test methods are found to be dependent upon the va riation of localized stress in the samples due to the different loadin g configurations and often give different results. Using Raman spectro scopy it is shown that the strain-dependent shift of the 1610 cm(-1) a ramid Raman band can be used to determine the point-to-point variation of axial fibre strain along aramid fibres embedded in epoxy resin mat rices from which the interfacial properties can be derived. The interf acial properties of aramid/epoxy model composites have been determined using Raman spectroscopy where the properties of the fibre, including different surface treatments, and the matrix have been changed system atically. The results are reviewed here and compared to those obtained using conventional micromechanical test methods. It is also demonstra ted that the Raman technique can be used to characterize the interfaci al properties of aramid/epoxy model composites deformed using differen t micromechanical test methods. In this way the interfacial properties can be determined at different loading levels enabling the progressiv e failure of the fibre/matrix interface to be monitored and defined ac curately.