The time to failure of carbon fiber-reinforced polymer composites is investigated during simultaneous compression and one-sided thermal degradation from a constant heat flux. The purpose of this investigation is to determine the rate of thermal degradation and mechanical property loss from fire exposure by observing the time to failure during simultaneous compression loading. A custom compression test fixture is designed and validated for use under thermomechanical loading. Testing is conducted on CFRP samples of varying thicknesses and quasi-isotropic layups. Test conditions are adjusted for a range of heat fluxes and compressive loads. Test parameters are isolated to observe individual impacts on time to failure. In each case, decreasing exponential trends are observed. High heat fluxes and high compressive loads result in shorter failure times. Temperature profiles are created based on heat flux exposure time and the position through the material thickness in order to determine failure criteria for thermomechanical loading. An empirical model is created to extrapolate and predict failure times using a stretched exponential function, based on mechanical preload, heat flux, and material thickness.

Carbon fiber-reinforced polymer (CFRP), noted for its outstanding properties including high specific strength and superior fatigue resistance, is increasingly employed in aerospace and other demanding applications. This study investigates the interactions between CFRP composites and high-energy lasers (HEL), with continuous wave laser powers reaching up to 120 kW. A novel automated sample exchange system, operated by a robotic arm, minimizes human exposure while enabling a sequence of targeted laser tests. High-speed imaging captures the rapid expansion of a plume consisting of hot gases and dust particles during the experiment. The research significantly advances empirical models by systematically examining the relationship between laser power, perforation times, and ablation rates. It demonstrates scalable predictions for the effects of high-energy laser radiation. A detailed examination of the damaged samples, both visually and via micro-focused computed X-ray tomography, offers insights into heat distribution and ablation dynamics, highlighting the anisotropic thermal properties of CFRP. Compression after impact (CAI) tests further assess the residual strength of the irradiated samples, enhancing the understanding of CFRP’s structural integrity post-irradiation. Collectively, these tests improve the knowledge of the thermal and mechanical behavior of CFRP under extreme irradiation conditions. The findings not only contribute to predictive modeling of CFRP’s response to laser irradiation but enhance the scalability of these models to higher laser powers, providing robust tools for predicting material behavior in high-performance settings.

Carbon-fibre epoxy panels have been subjected to rapid high temperature loads. The effects of temperature, exposure time and moisture content of the panels have been studied. It could be demonstrated that the combination of high moisture content and rapid heating can lead to excessive damage, such as sudden formation of delaminations up to the development of large bubbles on the panel. While it is well known that matrix and fibre–matrix interface strength generally decrease both with water uptake and temperature increase, a more severe damage mechanism has been observed here. The combination of high moisture content and rapid high temperature loads leads to an internal vapour pressure overload that can cause extensive cracks and delaminations. Subsequently, this permanent damage leads to serious changes in mechanical properties. Whereas heating dry panels to 350℃ for 1 h and testing them at room temperature reduced interlaminar shear strength less than 25%, many of the moist panels were fully destroyed within the first minute of heating.

This study focuses on observing and analyzing the time to failure of carbon fiber reinforced polymers subject to mechanical loading and one-sided heat flux simulating fire damage. The purpose of this investigation is to understand the rate of thermal degradation and mechanical property loss from fire exposure, resulting in catastrophic failure under simultaneous tensile loading. Composite samples of varying thicknesses and layup patterns are subject to a constant tensile load below the ultimate strength of the material. A thermal load is applied to one side by an infrared band heater, emitting a constant heat flux. The time to failure is monitored to determine how long the material can withstand this combined loading condition. A consistent trend is observed for various heat flux settings. High mechanical loads contribute to a shorter time to failure, and low mechanical loads contribute to a longer time to failure. Similarly, higher heat flux settings result in shorter failure times, and lower heat flux settings result in longer failure times. Temperature profiles are created based on heat flux exposure time and position through the sample thickness, establishing failure criteria for different loading conditions. The resulting trends are observed and extrapolated to create a predictive model using an Arrhenius exponential decay function.

Instrumented impact testing and compression-after-impact testing are important to adequately qualify material behavior and safely design composite structures. However, the stresses to which fiber-reinforced plastic components are typically subjected in practice are not considered in the impact test methods recommended in guidelines or standards. In this paper, a test setup for investigating the impact behavior of composite specimens under plane uniaxial and biaxial preloading is presented. For this purpose, a special test setup consisting of a biaxial testing machine and a specially designed drop-weight tower was developed. The design decisions were derived from existing guidelines and standards with the aim of inducing barely visible impact damage in laminated carbon fiber-reinforced plastic specimens. Several measurement systems have been integrated into the setup to allow comprehensive observation of the impact event and specimen behavior. A feasibility test was performed with biaxially prestressed carbon fiber-reinforced plastic specimens in comparison with unstressed reference tests. The compressive-tensile prestressing resulted in lower maximum contact forces, higher maximum deflections, higher residual deflections and a different damage pattern, which was investigated by light microscopic analysis. Finally, the functionality of the experimental setup is discussed, and the results seem to indicate that the test setup and parameters were properly chosen to investigate the effect of prestresses on the impacts behavior of composite structures, in particular for barely visible subsequent damages.