Effects of RTM Mold Temperature and Vacuum on the Mechanical Properties of Epoxy/Glass Fiber Composite Plates

Abstract

The purpose of this study is to investigate the effects of mold temperature, application of vacuum at resin exit ports, and initial resin temperature on the mechanical properties of epoxy matrix woven glass fiber reinforced composite specimens produced by resin transfer molding (RTM). For this purpose, six mold temperatures (25, 40, 60, 80, 100, and 120°C), two initial resin temperatures (15 and 28°C), and vacuum (0.03 bar) and without vacuum (~1 bar) conditions are utilized. Specimens are characterized by ultrasonic C-scan inspection, mechanical tests (tensile, flexural, and impact), thermal analyses (ignition loss and TGA) and scanning electron microscopy. It is observed that mechanical properties of the specimens produced at a mold temperature of 60°C with the application of vacuum and initial resin temperature of 28°C proved to be the highest (e.g., 16, 26, and 43% higher tensile strength, flexural strength, and Charpy impact toughness, respectively, compared to the lowest values attained with mold temperatures other than 60°C while other variables are kept constant). It has been shown that application of vacuum contributes to the final mechanical properties of the produced composites by lowering the percentage of `voids'. In fact, without the application of vacuum, the deteriorations in mechanical properties are as high as 26% loss in Charpy impact toughness and 5% losses in tensile and flexural strength. Additionally, lowering the initial resin temperature is shown to alter mechanical properties (e.g., 14, 12, and 18% losses in tensile strength, flexural strength, and Charpy impact toughness, respectively, when the initial resin temperature is decreased from 28 to 15°C).