Marie-Laetitia Pastor

Damage of woven composite under tensile and shear stress using infrared thermography and micrographic cuts

AbstractInfrared thermography was used to study damage developing in woven fabrics. Two different experiments were performed, a ±45° tensile test and a rail shear test. These two different types of tests show different damage scenarios, even if the shear stress/strain curves are similar. The ±45° tension test shows matrix hardening and matrix cracking whereas the rail shear test shows only matrix hardening. The infrared thermography was used to perform an energy balance, which enabled the visualization of the portion of dissipated energy caused by matrix cracking. The results showed that when the resin is subjected to pure shear, a larger amount of energy is stored by the material, whereas when the resin is subjected to hydrostatic pressure, the main part of mechanical energy is dissipated as heat.

Bonded repair issues for composites: An investigation approach based on infrared thermography

An original approach based on active Infrared Thermography (IT) addresses the very challenging issue of the nondestructive analysis of bonded repaired CFRP laminates. Difficulties come from the weak property contrast between parts of repaired assemblies and thickness of the joint. Strong attention is given here to the control of experimental tests conditions (heat load, boundary conditions), which allows to develop a physically consistent numerical model of the thermal problem. Comparison between measured and simulated surface temperature fields shows very good agreement regarding temporal and spatial evolutions for composites with different lay-up and offers new solutions for the NonDestructive Testing (NDT) of bonded repaired composites.

Thermographic investigation of heat source in transversely isotropic composites

This paper deals with the estimation of heat sources from infrared thermographic measures on anisotropic CFRP (Carbon-Fibre Reinforced Composites). Such procedure combines the data processing of the thermal signal, especially as spatial and temporal derivation quantities involved in the heat equation are notably affected by the measurement noise, and the determination of thermo-physical properties of the material, especially to account for the anisotropic conductivity behavior of the material. A comparative analysis of different filtering techniques is done to define a filtering method able to decrease the noise while keeping the useful features of the signal. Then, we use a homogenization scheme based on single-inhomogeneity solutions of Eshelby to derive the transversely isotropic thermal conductivity tensor.