Dynamic capillary effects in liquid composite moulding with non-crimp fabrics

A technique is presented to measure the capillary pressure drop ΔPγ during infiltration of non-crimp fabrics by a liquid matrix. Three types of liquids are used: polyethylene glycol (PEG) dissolved in water, a thermoset epoxy resin and a reactive thermoplastic system. Results show that epoxy resin behaves as a non-wetting liquid with a ΔPγ of 14 kPa when injected under constant pressure. The PEG and the thermoplastic system exhibit a wetting behaviour with ΔPγ of −5.4 and −13.8 kPa, respectively. Constant flow rate experiments furthermore indicate that ΔPγ increases with the fluid velocity, closely following the velocity dependence of the dynamic wetting angle. Thus, a thermodynamically wetting resin may well behave as a non-wetting fluid during Liquid Composite Moulding, when viscous forces dominate over capillarity.