ISSN 2347-3487 Volume 11, Number 8 Journal of Advances in Physics 3940 | Page council for Innovative Research May 2016 www.cirworld.com Effect of mechanical consolidation on adhesion mechanism of hybrid non-woven Alfa fibers reinforced unsaturated polyester composite A.TRIKI 1,* and Med BEN HASSEN 2, 3 1 Laboratoire des matériaux composites, polymères et céramiques, FSS 3018, Université de Sfax, Tunisia. *Corresponding author : trikilamacop@yahoo.fr 2 Laboratoire de génie textile, Université de Monastir, ISET Ksar Hellal, Tunisia . 3 College of Engineering, Industrial Engineering Department, Taiba University, Saudi Arabia benrayen@yahoo.fr ABSTRACT Vibrational analysis based on FTIR measurements were performed on hybrid non-woven Alfa fibers reinforced unsaturated polyester composite (HNWAFRUP) and its constituents. The reinforcement was made up of Alfa and wool fibers in the relative volume fractions ratio 4:1. These non-woven fibers sheet were consolidated mechanically by means of the needle punching. This study revealed that the increase of passages numbers in this device allowed the separation of the Alfa fibers and the reduction of the ligni n’s component in these fibers which decreased its hydrophilic character. Chemical reactions between wool and Alfa fibers were based mainly on the appearance of new vibrations originating from wool fibers in the reinforcement. Adhesion mechanism between the matrix and the reinforcement was established by chemical bonds formed by secondary bonding. Tensile testing performed on this composite revealed the enhancement of its mechanical properties attributed to a less fiber to fiber contact of wool fibers. Nevertheless, the decrease of its specific Young’s modulus revealed the mechanical consolidation effect on Alfa fibers/matrix adhesion. Keywords: Adhesion; Mechanical consolidation; FT-IR; Wool fibers; Hybrid composite. 1. INTRODUCTION Bio-composites have attracted the attention of many researchers and industrials due to the numerous advantages of natural fibers as reinforcement in these polymeric materials [1]. These composite materials are mostly used in construction [2-6] and automotive [7-9] fields. Nevertheless, the growth of natural-fiber composites cannot be carried out without any challenge. Indeed, the hydrophilic character of this reinforcement could limit its compatibility with the hydrophobic polymeric matrix and hence reduces the mechanical properties of the composite if moisture is absorbed as they age [10]. Interfacial adhesion and resistance to moisture absorption of natural fiber composites can be improved by the suitable modification of fibers surface [11-13] or by modifying matrix to make it more compatible with cellulose fibers [14]. Further, physical treatment based on hybridization with glass fibers provides a method to improve the mechanical properties of natural fiber composites [15]. In our previous work, we have evidenced that hybridization with wool fibers could be considered as ecological surface treatment of Alfa fibers in the unsaturated polyester hybrid composite [16]. The present work is focused on the effect of the mechanical consolidation of non-woven Alfa fibers, using a needle punching, on their adhesion in unsaturated polyester composite. In this study, hybridization treatment of Alfa fibers with wool fibers in the relative volume fraction ratio 4:1 was taken into account. Vibrational analysis based on FT-IR measurements was performed on the composite and its constituents so as to evidence the effect of the passages numbers increase of needle punching on hydrophilic character of the reinforcement and on the chemical interactions occurred between Alfa and wool fibers. The adhesion mechanism was determined by this vibrational study. Tensile testing was carried out on this composite in order to confirm this study. 2. MATERIALS AND METHODS 2.1 Materials The unsaturated polyester (UP) resin used as the matrix was the same as that used in our previous study [17] and was supplied by Cray Valley/Total. The reinforcement of non-woven fibers (Alfa, wool) was elaborated in the similar steps described in our previous study too [18]. The HNWAFRUP composite was manufactured using the classical ‘contact mould method’ [19]. Fibers were deposited on the mould and then impregnated with the liquid resin mixed with suitable proportions of methyl ethyl ketone peroxide and cobalt octanone as hardener and catalyst, respectively. The saturated material was then pressed by a roller to remove bubbles. After the hardness of the resin, the composite was withdrawn from the mould. The volume fraction of the reinforcement for this HNWAFRUP composite was 7.4 %. 2.2 Methods The IR spectra were recorded on a Perkin Elmer UATR two spectrometer, in a reflection mode, between 4000 and 400 cm -1 with a resolution of 2 cm -1 . The preparation of the sample for this characterization was explained previously [20]. Tensile testing was carried out with a Lloyds dynamometer universal testing machine as per NF T 57-301 at a crosshead speed of 5 mm/min and a gripping length of 100 mm. The composite was cut out in the direction of nonwoven production. Obtained results were calculated as the average of ten samples.