A ROUND-ROBIN PROGRAM ON INTERFACIAL TEST METHODS

A round-robin programme has been undertaken to assess the compatibility in the micromechanical techniques used to evaluate the interfacial shear strength of the fibre/matrix bond in composite materials. The tests selected for evaluation were the single-fibre pull-out test, the microdebond test, the fragmentation test and the micro-indentation test. Twelve laboratories were invited to participate in this programme. Each laboratory was supplied with Caurtaulds XA fibre in the untreated condition and with a standard surface treatment, and a quantity of epoxy resin, hardener and catalyst, all from the same batch. Some laboratories were supplied with composite bars made with the same materials. A common cure cycle was chosen for sample preparation. Each laboratory conducted the tests to its own procedures. The results showed that the scatter within each laboratory was acceptable but the scatter between laboratories for a particular test was high. The results are discussed and possible explanations are presented for these observations. The indications are that the fundamental procedures used in each laboratory are sound. The results also suggest that there is great potential for achieving standard procedures and reducing the inter-laboratory scatter. A further round-robin programme is proposed to generate test protocols.