Aero engines re-dressed with composite pipes
Engineering non-metallic pipes and fittings that replicate existing components was incredibly challenging for the partners of the EU-funded project COMPIPE (Composite pipes and fittings for aero-engines dressing). The resulting pipe assemblies must be capable of withstanding the rough operating environment of an aero engine. Specifically, pipes must withstand pressures up to 31 bars, temperatures up to 165 °C, and corrosion from contact with hydraulic fluids, oils and aviation fuel. Moreover, the harsh aero engine environment includes exposure to vibration and general abuse. Depending on their location, pipes must also be fire resistant or fireproof. The COMPIPE partners started by comparing the state of the art for metallic aero engine pipes and composite pipes used in a variety of applications. Options included thermoset and thermoplastic materials. In the end, braided carbon fibre-reinforced polymers (CFRPs) provided the best combination of performance and formability. Next, a variety of designs and materials for pipe connectors and end fittings were explored. After investigating a wide variety of methods, researchers adapted metal techniques to composites and developed a proprietary process that enables high-accuracy joining of the end fittings to the composite pipes. The last challenge was to prove the capabilities of the braided CFRP to pass the required tests. After more than two and a half years of research, the composite material could be moulded and post-formed into complex shapes. Importantly, the final products meet stringent test requirements for both fire-resistant and fireproof applications. The project team has succeeded in bringing aero engine dressing into the 21st century. Pipework design concepts and components had remained almost the same for a long time. For example, there is little difference in materials and components used in the dressing of the latest Rolls-Royce Trent aero engine and the RB211 from the 1970s. COMPIPE has also proven that a modest weight reduction in a single fitting can have an immense effect on the overall cost and environmental impact of manufacturing and flying an aircraft. Initial estimates demonstrate that huge savings that can reach 10 kg per engine are possible with the new technologies.
Keywords
Aero engines, composite pipes, aircraft, COMPIPE, fire resistant, CFRPs
