673 MECHANICAL CHARACTERIZATION AND OPTIMUM DESIGN OF WOUND GLASS-FIBER-REINFORCED POLYMER PIPES BASED ON THE WINDING ANGLE AND THE NUMBER OF PLIES B. Baali, 1* A. Benmounah, 1 and M. Rokbi 2 Keywords: wound structures, glass-reinforced polyester, angle-ply reinforcements; Composite Pipes. The design of composite structures is always a very delicate task to ensure that an antisymmetrically wound laminate had the performance required. Our study was carried out with the aim to optimize the performance/ cost ratio of these materials. It consisted in the design and manufacture of orthotropic flament-wound glass- reinforced polyester (GRP) pipes with different fber orientation (± 45, ± 55, and ± 70°). Experiments on a 500-mm-diameter GRP pipes wound at different angles were carried out in various mechanical loadings, and the data found were compared with results obtained by analytical methods. 1. Introduction The pipe industry has been interested in composite materials since the 1950s. The interest in glass-fber-reinforced polymer (GFRP) pipes is mainly due to their light weight combined with high mechanical characteristics, good corrosion resistance, and improved fatigue behavior compared with steel and aluminum alloy ones [1, 2]. Furthermore, GFRP pipes have become indispensable in many applications owing to this combination of properties. The pipeline industry has benefted from civil and military investigations by adapting composite materials to its own needs [3, 4]. Nowadays, the use of composite pipes is growing with the possibility of developing high-performance materials, and they are often used in almost all applications to withstand aggressive service, ambient temperature, and environmental conditions [1, 2, 5]. Mechanics of Composite Materials, Vol. 56, No. 5, November, 2020 (Russian Original Vol. 56, No. 5, September-October, 2020) 1 URMPE, Faculty of Technology, M. Bougara University, Boumerdes 35000, Algeria 3 Department of Mechanical Engineering, Faculty of Technology, University of M’sila, 28000, Algeria * Corresponding author; tel.: +213 550 561 664; e-mail: b.baali@univ-boumerdes.dz 0191-5665/20/5605-0673 © 2020 Springer Science+Business Media, LLC Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 56, No. 5, pp. 977-992, September- October, 2020. Original article submitted November 8, 2019; revision submitted May 8, 2020. DOI 10.1007/s11029-020-09912-3