Analysis of composite reinforcement at mesoscopic scale from X-ray microtomography

摘要

During the pre-forming stage of the RTM process, large deformations can occur, especially for double-curved shapes. Knowing the mechanical behaviour and the actual geometry of fibrous reinforcements at the mesoscopic scale is of great importance for several applications like permeability evaluations. As such, forming modeling is particularly demanding on the quality of geometric modeling and on the mesh associated. Indeed, analysis of the internal structure of materials in general, and woven materials especially, recently led to major advances. X-ray Micro Tomography (XRMT or μCT) allows detailed and accurate 3D observations inside the sample, which is not possible with the standard microscopy techniques restrained to surface observations. It distinguishes the yarns and even the fibers that define the directions of anisotropy of the material. A FE model is generated from the processed tomography images. It has been chosen in this study to use hypoelasticity behaviour law. Indeed, the yarns are submitted to large deformations, so that the orientation of the material is significantly modified and the fiber direction has to be strictly followed in order to fulfil the principle of objectivity. A way to retrieve the neutral composite reinforcement axis by skeletonization is proposed in order to know the privileged direction of the yarn and thus implement it in the constitutive law. A comparison between experimental and simulations obtained from μCT and idealized geometry of a transverse compression test on the G0986 is presented.