Effect of repeated thermal cycle on compressive properties of cyanate ester/quartz-based composites

Abstract

The continuous fibre reinforced polymer composites are used in electronic circuits and radar radomes of defence aircraft due to lower transmission loss in the broadband microwave frequency region. Quartz fibre-reinforced cyanate ester composites are one of the best-suited materials for the radome structure of an aircraft offering exceptional electromagnetic transparency in varying operational temperatures. Moreover, this material possesses high-temperature capability with excellent mechanical and dielectric properties. The radome structure usually undergoes multiple thermal cycles during fabrication. In this work, to determine the compressive strength, a quartz/cyanate ester laminate was prepared with repeated thermal infusion followed by final curing (CE/Q_M) using resin film infusion (RFI) technique. The volume fraction of fibre, resin and void fraction were evaluated using the resin-burn off method. Finally, Ultrasonic C-scanning, a non-destructive quality evaluation and raster scanning using a multi-axis squirter system was carried out to detect and characterize the defects induced in the laminate. These data were compared to a sample produced with regular infusion followed by a curing cycle (CE/Q_S). The compressive strength of CE/Q_M (372.48 MPa) is measured to be 12% more than that of CE/Q_S (332.084 MPa). This is attributed to increased crosslink density in CE resin and strong interfacial adhesion between the resin and the fibre in the latter due to multiple thermal infusion cycles.