Papers by Author: A. Vautrin

Abstract: This article presents a first approach of hygrothermal microcracking in stitched crossply laminates. The presentation includes the definition of the material mesostructure and the selection of a characterization method adapted to the specificity of the study. The hygrothermal loading selected is discussed and the evolution of the crack density in stitched crossply composites during the loading is presented and commented.

Abstract: Optical Full Field Techniques (OFFT) are more and more utilized by mechanical laboratories. Among these methods, interferometry techniques (mainly composed of Speckle/Grating Interferometry or Speckle/Grating Shearography) are more difficult to use in a mechanical lab context, because of their sensitivity to external vibrations (except shearography), and because of the global lack of optical culture of mechanical engineers. Speckle-based methods are of great practical interest for the users, but their signal to noise ratio (SNR) is affected by the rigid body motion of the specimen. Here, the speckle decorrelation is minimized at local scale directly using the SNR. First, a shearography experiment is modeled to characterize the recorrelation procedure for a rigid body motion, a constant strain map and finally a high degree of localization. The mean noise level is found to be 6 times higher than a fully-correlated phase map for a 1 pixel speckle size. Last, a first application to a single-ply fabric composite lamina is shown. Resulting strain maps are of high quality with a very low spatial resolution (4 pixels). The local bending / global tension coupling effect is clearly put in evidence.

Abstract: The deformation of free laminated plates subjected to transient hygrothermal loading is simulated by using a semi-analytical non linear model (variational method). A full-field experimental technique, the fringe projection method, has been developed to measure out-of-plane displacements throughout the deformation process. The experimental approach based on a full-field optical method is shown to be suited to capturing the complex behaviour of plates submitted to large hygrothermal loads, where geometrical nonlinearities should be taken into account.