Influence of different glass fiber sizings on selected mechanical properties of PET/glass composites

The properties of fiber-reinforced plastics are considerably influenced by fiber-matrix interaction. The aim of this study was to investigate the infl uence of glass fiber surface treatments on the morphology of poly(ethylene terephthalate) (PET) and on selected mechanical properties of unidirectiona l PET/glass fiber composites. The materials used here were E-glass fibers t reated with model sizings including aminosilane as a coupling agent and pol yurethane and epoxy resin dispersions as film formers and PET as the matrix . For identification of the degree of crystallinity of the PET matrix, diff erential scanning calorimetry (DSC) was used. To study the influence of the different sizings on the mechanical properties, the following tests were p erformed: interlaminar and intralaminar shear tests and a transverse tensil e test. Dynamic-mechanical analysis (DMA) was used to characterize the beha vior of the composites under dynamical load. The DSC results show that the overall crystallinity and the melting behavior of the PET matrix were hardl y influenced by the glass fiber surface treatments used. The various streng th properties of the composites are influenced not only by the silane coupl ing agent, but also by the type of film former. With an epoxy resin dispers ion, the mechanical properties were enhanced compared with a polyurethane d ispersion. These results were confirmed by characterization of the composit es by DMA.