Microstructural observations supporting thermography measurements for short glass fibre thermoplastic composites under fatigue loading

Abstract

This paper combines the infrared thermography and the computed laminography techniques to better understand the mechanisms of damage under fatigue for a short fibre-reinforced thermoplastic material. Depending on the experimental technique used, the measurement implies a "homogenization" of the values deduced over a prescribed volume. The real volume contributing to the thermal fields and thus the dissipated energy evaluated from thermography cannot be easily determined. The laminography technique provides precious insights for the determination of the dissipation fields, by providing a clearer view of the in-depth notch front profile as well as the local fibre orientation and by giving an idea of the volume change induced by porosity. In turn, the latter may affect the physical (thermal) constants used in the determination of the dissipated energy.

Modeling the high‐cycle fatigue crack initiation in short fiber reinforced polymers with notches

“…When the notch profile is not machined but injected, the fiber orientation and distribution is strongly affected by the mold flow perturbation caused by the notch flanks. 10,21,[30][31][32] This perturbation involves the regions close to the notch, which are the most critical for the crack initiation. The fatigue behavior is thus largely influenced by the local fiber distribution.…”

Comparing Methods to Detect the Formation of Damage in Composite Materials

“…When the energy is released under the form of heat, the temperature increase caused by alterations of the material can usually be picked up using infrared thermography, a commonly used Non-Destructive Testing (NDT) technique to detect damage in composites [1][2][3][4]. The heat fluctuations caused by thermoelasticity can also be detected, which is commonly used to study fatigue [5][6][7]. Active thermography is a technique used to extract information from the heat conductivity of the material by recording the transient behavior of a sample [8].…”

Using Quantitative Passive Thermography and Modified Paris-Law for Probabilistic Calculation of the Fatigue Damage Development in a CFRP-Aluminum Hybrid Joint

“…Thus, facilitating the correlation of the location-dependent amount of temperature-variation with macroscopic mechanical measurands [ 2 ], it provides the possibility of contemplating inhomogeneous stress states in hybrid-joints. This procedure can be found in the state-of-the-art literature for determination of stress-distribution [ 3 ] and mainly for qualitative detection of defects [ 4 ], whereas damage assessment methods ask for new approaches crosslinking quantitative NDT information and fracture mechanics.…”

“…Regarding non-destructive testing as a damage characterization technique, thermography was often applied under quasi-static [ 3 , 4 , 27 ] and fatigue loading [ 28 ]. Thereby, convenient thermal properties of CFRP have led to thermography signal mapping, with hot spots indicating the failure location [ 27 , 29 , 30 ].…”