ENGINEERING FOR RURAL DEVELOPMENT ELASTIC PROPERTIES OF COTTON FABRIC BASED POLYMER COMPOSITIES

Abstract. The paper presents analytical and experimental procedures for estimating elastic properties of a plain weft-knitted fabric and of polymer composite materials reinforced by it. Cotton yarn and fabrics are being considered as an environmentally friendly alternative to synthetic reinforcement in polymer composites. In the present investigation, cotton yarn of different length and cotton knitted fabric specimens of different knitting directions were tested by tension in order to obtain the stress-strain response. Elastic modulus of the cotton yarn and knitted fabrics, having different load span and knitting directions, were obtained. Cotton knitted fabric composites with thermoset polymer matrices were manufactured and tested for stiffness and strength. Based on the Leaf and Glaskin model, a numerical (FEM) elastic properties averaging model was elaborated. Calculated elastic properties of composite materials have shown high compatibility with experimentally obtained values. Keywords: cotton yarn, cotton knitted fabric, elastic modulus, textile composites. Introduction Using knitted fabric as polymer composite reinforcement is gaining much interest during the last decades because of its attractive mechanical properties, energy absorption, impact resistance, etc. and technological advantages -excellent stretch ability, shape forming ability and flexibility, which allows it to be used in any complex shape mould without folds In order to effectively predict the properties of a composite, it is necessary to know the properties of the reinforcement. Mechanical properties of the yarn are traditionally measured experimentally. For the knitted fabric geometrical modelling is important [7; 8]. In papers [9; 10] also the plain knitted fabric was investigated and geometrical models were created. In the recent papers a new model was created by assuming that the orthogonal projection of the yarn path is formed of smoothly connected arcs. Different modelling of the geometrical structure of the knitted fabric is considered in [11; 12]. Knitted fabric reinforced composites have been investigated experimentally (for different fibres and matrices) and theoretically (elaborating analytical or numerical models) [2; 4; 6; 13-16]. Theoretical investigation of mechanical properties is based on averaging procedures used in combination with some assumptions about the internal geometry of the reinforcing fabric