Flexural and interlaminar shear properties of glass-reinforced phenolic composites

Low-temperature acid-cured resole phenolic resins and glass-fibre-reinforced polymer (GRP) composites containing resole matrices are inherently fire-retardant materials that evolve low levels of smoke and combustion products in a fire. The mechanical properties, particularly interlaminar shear strength (ILSS), of glass/phenolic composites are low compared with those of glass/polyester composites, and this is discussed in terms of the compatibility between the reinforcing fibres and resin matrix, the influence of the phase-separated water microdomains which result in voids in the phenolic matrix, and the resin strength. An epoxy silane coupling agent on the glass fibre in a glass/phenolic composite resulted in a significantly higher ILSS and flexural strength than an aminosilane, which is recommended for use with thermally cured glass/phenolic composites, or a methacrylyl-functional silane, which is preferred for use with glass/polyester and glass/vinyl ester composites. The ILSS of the glass/phenolic composites decreased after exposure to water at elevated temperature; this is attributed to a deterioration of the interfacial region and is independent of the silane coupling agent used on the glass reinforcement. (C) 1998 Elsevier Science Ltd. All rights reserved.