A ROUND-ROBIN PROGRAM ON INTERFACIAL TEST METHODS

A round-robin programme has been undertaken to assess the compatibilit y in the micromechanical techniques used to evaluate the interfacial s hear strength of the fibre/matrix bond in composite materials. The tes ts selected for evaluation were the single-fibre pull-out test, the mi crodebond test, the fragmentation test and the micro-indentation test. Twelve laboratories were invited to participate in this programme. Ea ch laboratory was supplied with Caurtaulds XA fibre in the untreated c ondition and with a standard surface treatment, and a quantity of epox y resin, hardener and catalyst, all from the same batch. Some laborato ries 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 discusse d and possible explanations are presented for these observations. The indications are that the fundamental procedures used in each laborator y are sound. The results also suggest that there is great potential fo r achieving standard procedures and reducing the inter-laboratory scat ter. A further round-robin programme is proposed to generate test prot ocols.