Characterization of one-sided thermal damage of carbon fiber reinforced polymers by means of depth profiles

Abstract

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.

Predicting Delaminations and Residual Strength of Carbon Fibre Reinforced Polymers (CFRP) After One-Sided Thermal Loading by Means of Infrared Spectroscopy

“…ATR-FTIR-spectroscopy proved itself as an appropriate non-destructive testing method for the detection of matrix degradation in CFRP after thermal loading [11][12][13][14][15][16][17][18][19]. Figure 2a shows an IR spectrum of 8552/IM7 CFRP without thermal loading.…”

“…With increasing exposure time and temperature, mechanical properties like compressive and tensile strength decrease [6][7][8][9][10]. Also, interlaminar shear strength (ILSS) decreases with increasing thermal loading due to its sensitivity towards structural damage like, e.g., delaminations [8,[11][12][13]. For understanding this decrease, a closer look is necessary on the single degradation phenomena such as structural damage (e.g., delaminations) or the chemical decomposition of the polymer matrix (matrix degradation) and their distribution inside the CFRP [6,9].…”

“…Thermally induced structural damage inside the CFRP like, e.g., delaminations can be analyzed with different non-destructive testing methods like, e.g., microfocused computed X-ray tomography (µCT) or ultrasonic testing [6,[13][14][15][16]. Especially µCT enables the detection of small delaminations due to its resolution in the micrometer-scale compared with other non-destructive testing (NDT) methods.…”

“…For analyzing matrix degradation as a consequence of thermal loading, infrared spectroscopy (ATR-FTIR) is a convenient tool [11][12][13][17][18][19][20]. Especially hand-held ATR-FTIR-spectrometers provide the advantage of measurements directly at an, e.g., thermally damaged aircraft [21,22].…”

Study of thermomechanical coupling in carbon fibers woven‐ply reinforced thermoplastic laminates: Tensile behavior under radiant heat flux

“…Most references dealing with the fire behavior of PMCs are related to thermosetting (TS) matrix composite materials, [12][13][14][15][16][17][18][19][20][21][22][23][24][25] which have been used for almost 40 years in these sectors (carbon/epoxy, carbon/phenolic, glass/ vinylester, or glass/polyester). From the end of the 1990s, the use of thermoplastic (TP) matrix composite materials has been developing in many industries.…”