MECHANICAL TESTING OF COMPOSITE SPECIMENS MADE BY RFI TECHNOLOGY

The present paper provides a description of the RFI (Resin Film Infusion) method and influence of the polymer epoxy systems and their reinforcements on the mechanical properties of the whole composite specimen. Typically, the RFI element consists of a thermoset resin film placed between one side of a metal tool and a dry textile fiber preform. Then, a bag connected to a vacuum pump and processed under a selected thermal curing cycle closes the whole system. RFI technology has gone through some changes since it was discovered. One of the RFI varieties is LF-Technology (Letoxit Foil) provided by local Czech producer 5M Ltd. LF Technology, developed and patented by 5M Ltd., is a very efficient technique for producing sophisticated and relatively cheap composite structures. Part A: The composite specimens were prepared from various types of reinforcements and matrices, as noted below. The basic experimental part of the research program was focused on the property verification of two polymer epoxy matrix systems applicable to RFI technology. Glass (plain and twill weave), carbon (plain and twill weave), hybrid - Carbon/Kevlar (plain weave) and basalt (plain weave), reinforcements were used. In the experimental part of this work, tests on the mechanical properties were made. These properties (Flexural strength, interlaminar shear strength [ILSS] and impact toughness) were chosen because of their fast orientation in material properties and the state of the finished composite part. Test specimens were prepared by 5M Ltd. Borsice u Buchlovic, Czech Republic, Europe. Part B: Other samples of hybrids (Basalt/Kevlar) and UD (unidirectional) composites were fabricated and tested at the IAE (Institute of Aerospace Engineering), Brno University of Technology. The epoxy resin foils LFX023, LFX032 and LFX035 were applied. Part C: In this part unidirectional (UD) materials were tested. Thanks to the resin properties it was easy to get clear material after selecting the right curing cycle. LF Technology gives freedom to designers, helps push down prices of composite products and increases properties and reliability, which is supported by favorable responses from customers and quick and relatively easy development of new products. All these advantages promise a very good future for LF Technology [9].