Title Effect of Reactive Finishes on the Moisture Durability of Carbon/Vinyl Ester Laminates
Source Proc. SAMPE 2010 Symp. and Exhib.
Year 2010
Author(s) Allred, R. E.; Haight, A. E.; Wesson, S. P.
Abstract This study was undertaken to determine the moisture durability of unidirectional T700 carbon/vinyl ester laminates with various fiber surface treatments. A previously developed solvent-based finish for carbon/vinyl ester was modified to be applied also as an aqueous emulsion. The finish is composed of a reactive coupling agent, a low viscosity vinyl ester resin, a free radical inhibitor, and a surfactant. The reactive finishes were successfully applied to unsized T700 fibers. Bromine analysis of the finished fibers showed the presence of the desired residual vinyl groups in the fiber surface coating that can chemically bond to the vinyl ester matrix during composite processing. Unidirectional laminates containing several types of fiber surfaces (Toray FOE sized, and reactive finishes of two lots) were machined into test specimens. Those specimens were exposed to high humidity and temperature until saturated and mechanically tested using interface sensitive test methods (transverse flexure, short beam shear) and a fiber dominated test (longitudinal flexure), and characterized for failure mode. Moisture absorption kinetics, mechanical properties, and fracture surface analysis results show that the reactive finishes substantially improve the carbon/vinyl ester interface-dominated mechanical properties compared to the FOE sized materials. In addition, the toughness of the interface in shear as seen in the area under the load-deflection curves is substantially increased as well. Failure mode analysis shows that interfacial failure dominates the saturated FOE sized materials, whereas resin cohesive failure dominates the ATI finished materials. This is a strong indication that the desired chemical bonding is occurring at the T700/vinyl ester interface through the reactive finish.
Keywords reactive, moisture durability, carbon, vinyl ester, laminates, aqueous emulsion, coupling agent, free radical inhibitor, surfactant, interface, mechanical properties, toughness