Short Communication Impact of sea and tap water exposure on the durability of GFRP laminates Saud Aldajah a, * , Ghydaa Alawsi b , Safaa Abdul Rahmaan b a United Arab Emirates University, Al-Ain, United Arab Emirates b University of Technology, Baghdad, Iraq article info Article history: Received 8 May 2008 Accepted 15 July 2008 Available online 31 July 2008 abstract Environmental exposure has undesired impact on the mechanical and physical properties of composite materials. This paper studies the impact of sea and tap water exposure on the mechanical and physical characteristics of symmetric and anti-symmetric eight-layer glass fiber-reinforced polymer (GFRP) com- posite laminates. Three-point bending testing method and scanning electron microscope (SEM) were used in order to evaluate the mechanical and physical properties of the laminates. Results showed that symmetric laminates lost a total of 60% of the flexure stiffness and 55% when exposed to sea water and tap water environments, respectively, for 2000 h whereas, anti-symmetric samples lost 28% and 29.4% when exposed to the same environments respectively for 2000 h. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Engineering of modern composite materials has had a signifi- cant impact on the technology of design and construction. The ad- vanced composite materials are lighter, stiffer and stronger than any other structural material man has ever used. Composite mate- rials are ideal for structural applications where high strength-to- weight and stiffness-to-weight ratios are required. Aircraft and spacecraft are typical weight-sensitive structures in which com- posite materials are cost-effective. The development of air and space vehicles with their peculiar requirements of structures which need to be strong but light and flexible but tough, brought into being a new breed of hybrid structural materials, called fi- ber-reinforced composites. Glass fiber-reinforced polymer (GFRP) composites are often used in marine applications such as canoes, fishing trawlers, patrol boats and naval mine-hunting ships and in the non-pressure hull casing, sonar dome and masts of submarines. When used in marine applications it is essential that GFRP composites retain their mechanical properties and do not degrade when immersed in sea water for a long time. One major issue of using GFRP composites in sea water application is that the fiber/matrix interface is de- graded by a hydrolysis reaction of unsaturated groups within the resin. Sea water degradation can cause swelling and plasticization of the polyester matrix and debonding at the fiber/matrix interface that may reduce the mechanical properties [1–6]. The aim of this research is to assess the exposure of two envi- ronments (tap water and sea water) on the durability, moisture absorption behavior, degradation mechanisms and mechanical properties of symmetric and anti-symmetric GPR eight-layered composite laminates. In this paper, durability is defined as the ability of a composite material to retain its original physical, chemical and mechanical properties when immersed in tap water and sea water. The composites were immersed in tap water and sea water at a temperature of 22 °C. The effect of water absorp- tion on the fiber/resin interface region is examined using scanning electron microscopy. The effect of the two environments on the flexural stiffness and strength of the composites is also determined. 2. Sample preparation It is well known that the laminated composites consist of lay- ers of at least two different materials that are bonded together. Lamination is used to combine the best aspects of the constituent layers in order to achieve a more useful material. This definition quite fits with the class of laminated fibrous composites (com- posed of fibers in a matrix) in which the final composite product results from the layer stacking. Layers of fabric-reinforced mate- rial are built up with the fiber directions of each layer typically oriented in different directions to give different strength and stiff- ness in the various directions. The strength and stiffness of the laminated fiber-reinforced composites can be tailored to meet a specific design requirement. In this study, E-glass fibers and poly- ester resin matrix were used for the preparation of the laminated plates. Table 1 shows the mechanical properties of E-glass and polyester materials. The method that was used in the present work for preparing the laminated composite plates is the hand lay-up technique which is the oldest method that was used to get the composite materials as shown in Fig. 1. 0261-3069/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2008.07.044 * Corresponding author. Fax: +971 3 7623158. E-mail address: s.aldajah@uaeu.ac.ae (S. Aldajah). Materials and Design 30 (2009) 1835–1840 Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes