This study investigates one-sided thermal damage of carbon fiber reinforced polymers (CFRP) by means of depth resolved infrared spectroscopy, tomography and mechanical testing. All CFRP samples are thermally irradiated at one side with a heat flux of 50 kW/m2 over various time intervals. ATR-FTIR spectroscopy along a ground incline plane through the sample allows a chemical characterization of the thermal degradation of the polymer matrix into depth. Developing delaminations are observed with a depth-resolved gray-value-analysis of microfocused computed X-ray tomographic (µCT) data. Mechanical behavior is determined by tensile, compressive, and interlaminar shear strength (ILSS) testing of specimens taken from different depths of the irradiated samples. The depth profiles show how pronounced damage phenomena like matrix degradation and the development of delaminations are after one-sided thermal loading and how they influence strength in different ways. Compressive strength and ILSS is found to be more sensitive towards thermal damage than tensile strength, as they are most influenced by formed delaminations at higher thermal loads.

This study investigates the change of chemical, structural, and mechanical properties of carbon fibre reinforced polymers (CFRP) after one-sided thermal loading. Therefore, CFRP samples (HexPly® 8552/IM7) with varying thickness (4 and 8 mm) are irradiated at different heat fluxes (15, 30, and 50 kW/m2). For a depth-resolved view on matrix degradation inside the CFRP, infrared spectroscopy (ATR-FTIR) is applied along a ground incline plane. A change of structural properties in the form of developing delaminations is investigated with microfocused computed X-ray tomography (µCT). The loss of residual strength is determined by means of interlaminar shear strength testing (ILSS). The evaluation of the data shows that delaminations occur predominantly dependent on temperature and only beyond a certain level of matrix degradation traceable by IR spectroscopy. It is also shown that delaminations are mainly responsible for the loss of strength. Furthermore, linear discriminant analysis (LDA) is performed to predict the presence of delaminations. This information provides a basis for a reliable prediction of the residual strength by IR spectroscopy after one-sided thermal loading.

In this study, structural, mechanical, and chemical changes of one-sided thermally loaded carbon fiber reinforced polymers (CFRPs) are investigated. The aim is to test and reliably predict residual strength and delamination depth by using infrared spectroscopy. CFRP of different thicknesses (HexPly ® 8552/ IM7) were irradiated at varying heat fluxes over various time intervals. The inhomogeneously distributed matrix degradation was analyzed by means of attenuated total reflection Fourier transform infrared spectroscopy with a depth resolution of 0.2 mm. Residual interlaminar shear strength (ILSS) was determined and microfocused computed X-ray tomography was used to measure the delamination depth. Principal component analyses were performed to show which information in the infrared spectra is affected by thermal loading. Furthermore, the combination of spectra taken at different depths of the CFRP can be used to develop partial least squares regression models to predict ILSS and delamination depth. Despite an inhomogenous distribution of thermal damage, precise predictions of ILSS and delamination depth with models considering varying sample thicknesses and heat fluxes were achieved.