Viability of PEEK for high-temperaturemicrovascular composites manufacture

Sammanfattning: Microvascular composites are materials with an inner hollow network which allows thecirculation of fluids. This functionalizes the composite materials, giving them furtherapplications such as self-healing or active cooling. Some of the already existingmicrovascular composites are made with fiber reinforced epoxy resin with cavitiescreated by removal of a sacrificial low temperature resistant polymer insert. Currentresearch is focused on the obtention of microvascular composites that can withstandhigher service temperatures than epoxy, using polyimide as the high-temperature resinmatrix. The aim of this project is to find a suitable sacrificial material that will withstandthe higher curing temperatures of the polyimide while allowing its easy removal fromthe matrix. Three different candidate sacrificial materials were studied for this purpose:PEEK, PPS, and PC. Preliminary DSC test showed that the melting temperature of the PEEK was close to therange of the chosen resin. PPS melting temperature and PC glass transition temperaturewere below this range of curing temperatures. TGA test revealed that the degradationsuffered by the different materials at the curing temperature of the polyimide wasconsiderably low. A small-scale test mimicking the actual microvascular compositemanufacturing conditions was designed to study the actual behavior of the differentmaterials when heated. It was seen that both the PEEK and the PPS could not flowwithout applying extra pressure for the desired range of temperatures. Furthermore, ascaled model test revealed that there was no visible interaction between the differentmaterials tested and the polyimide resin. The initial study showed that PEEK and PPS arenot readily viable to use due to the apparent difficulties to remove them from thecomposite by just applying heat. PC was also considered not viable for this applicationsince it softened too much a too low temperature.