Evaluation of the adhesion level in aged composite-composite structures using ultrasonic waves
Résumé
Structural adhesive bonding based on carbon-epoxy composites is used in many sensitive industries such as aeronautics, automotive, renewable energy (blades of tidal turbines, blades of off shore wind turbines) due to their properties of light weight (reduce of fuel consumption) and the constraint repartition on the whole surfaces of the structure. These assemblies are exposed to severe environmental conditions (high variations in temperature, humidity, pressure and wind turbulence, etc.) and are therefore subject to structural aging. There is a strong industrial demand for effective non-destructive evaluation methods to control their health status during their use cycle. In this work are studied composite-composite bonded structures with different adhesion levels using ultrasonic guided waves, and that been subjected to different aging cycles (salt spray with different temperature gradients). The aim is to evaluate their properties changing using guided ultrasonic waves. The studied samples have different cohesive and adhesive controlled properties to improve or decrease the adhesion level. The discrimination of the different samples is performed using Lamb waves. A C-Scan characterization is performed on the structures to give images relating the real estate of the samples. A numerical rheological model based on interphases model which represents the bond substrate-adhesive by a thin layer is solved by Finite Element Method (FEM) using Comsol software. This predictive model makes it possible to classify the different levels of adhesion and to distinguish the aging effects on the different samples.