INTERFACE CHARACTERIZATION BY PULL-OUT TEST BETWEEN HIGH-MODULUS POLYETHYLENE FIBER AND AN UNSATURATED POLYESTER RESIN

The observation of the pull-out conditions for a monofilament outside a matrix has been applied to a wide variety of organic or inorganic ma terials, as a direct method of interface characterization. In the case of High Modulus PolyEthylene (HMPE) it has been demonstrated that oxy gen plasma treatments or gamma irradiation modify the fibre surface pr operties and improve the adhesion between the fibre and a resin. In th is study, the effect of different plasma treatment times and the irrad iation conditions leading to different gel fractions have been tested. For plasma treatments, an appreciable improvement occurs even for the lower residence times (2 sec). The gamma irradiation has only the sam e efficiency for the condition leading to a high gel fraction (0.75). These results agree with InterLaminar Shear Strengths (ILSS) values me asured in three-point bending on HMPE/epoxy laminates.