The current temperature limitations of Fibre Reinforced Polymer (FRP) composites may restrict their adoption in future lightweight vehicles. The effects of elevated temperature are complex, depending on the magnitude and duration of thermal exposure. In the short-term, glass transition causes thermo-mechanical performance reductions. In the medium term, the fibre-matrix interface can be irreparably damaged, while long exposures cause thermal ageing which may limit service life. A novel mitigating approach is active cooling of the material by circulating coolant fluid through embedded vascules. The fluid absorbs heat energy from the matrix and transports it to be rejected elsewhere. This novel concept may extend the FRP composite thermal performance envelope and improve service life. Carbon/epoxy specimens were exposed to short- and long-term thermal exposures. At 37 °C below Tg, non-vascular specimens suffered 10 % and 21 % reductions in in-situ flexural modulus and ultimate strength respectively, and after thermal ageing for 120 hours at 47 °C above Tg, they suffered residual flexural strength losses of 86 %. In identical specimens containing basic parallel vascule arrays, using moderate coolant flow rates of ambient temperature air, virgin material performance was almost completely retained in all cases. Surface temperatures were significantly reduced, and physical and chemical signs of thermal damage were both lessened. A finite volume model in MATLAB simulated the thermal performance of arbitrary vascular cooling networks. This was validated with good agreement to experimental specimen temperatures. This was then implemented into a basic genetic algorithm optimiser, demonstrating generation of an optimal design. This project validated the use of vascular cooling with air coolant in FRP composites, demonstrating performance retention in specimens across a range of thermal environments and time scales. It also added valuable evidence of the effects of elevated temperature on carbon/epoxy laminates.
Date of Award21 Jan 2021
Original languageEnglish
Awarding Institution
  • University of Bristol
SupervisorIan P Bond (Supervisor) & Andrew G W Lawrie (Supervisor)

Cite this