MECHANICAL PROPERTIES OF GLASS FIBRE-PET COMPOSITES BASED ON WEFT KNITTED PREFORMS G. Bogoeva-Gaceva 1 , G. Demboski 1 , I. Lacik 2 1 Faculty of Technology & Metallurgy, R. Boskovic 16, Skopje, Macedonia 2 Polymer Institute, Slovak Academy of Sciences, Dubravska cesta 9, Bratislava, Slovak Republic SUMMARY: The paper investigated influence of: hybrid yarn count, PET fibre characteristics and preform textile structure on weft knitted glass/PET composite mechanical properties. Weft knitted preforms were processed on flat bed knitting machine by simultaneously knitting PET and glass yarns. It was shown that composites from finer hybrid yarn provide higher mechanical properties and lesser variation of results. Composite from unsized undrawn PET fibres with lower crystallinity exhibits 30% higher mechanical properties, as compared to drawn/sized PET fibres, as a result of improved fibre/matrix bonding. Weft knitted preform structure could influence the composite's mechanical properties. KEYWORDS: fibre reinforced composites, glass fibre, DMTA, knitted fabric INTRODUCTION For the last few years the automotive industry has demanded environmental friendly, high performance, low cost and low weight engineering materials. This has given rise to research activities in the field of thermoplastic composites. It was shown that semi-finished textile preforms where matrix and reinforcement are intimately packed (hybridized) in fibrous form could be the right answer to such demands. Such preforms could be in a form of hybrid yarns and hybrid fabrics [1, 2]. Textile engineering has also responded to such demands by invention of structures and machines for technical application [3-6]. There are number of textile structures that could be applied in preforms production. Woven, warp knitted, braided and nonwoven have been intensively studied [7-11]. Weft knitted structures have also been researched [12-14], as they can successfully fulfill the gap in mechanical properties between short and long fibre reinforced composites [15]. The potential advantages for application of weft knitted composites are: high productivity; excellent drapeability; convenient for application of deep drawing techniques; near net shape manufacturing of fibre preforms; possibility of production of double curved structures with no folds; easy of handling; production of integrated 3-D forms with almost no waste etc. Many factors influence mechanical properties of composites, among which are: fibre/matrix interfacial bonding,