A virtual permeability measurement framework for fiber reinforcements using micro CT generated digital twins

Liquid Composite Molding (LCM) is one of the widely used manufacturing techniques for high performance composite parts. In a simple LCM process, a pressurized liquid resin is injected inside a mold containing fibrous reinforcements. In order to create quality components using LCM processes, reinforcement characterization such as permeability and compaction response need to be performed fast and accurately. In this work, a micro CT based experimental-numerical reinforcement compaction and permeability characterization framework has been proposed which can potentially reduce process characterization cost by lowering material consumption and labor time and effort. The framework is non-destructive in nature and uses a miniaturized compression stage that can be housed in an X-ray computed tomography (XCT) system. This in-situ XCT experimental set-up is used to acquire the stress relaxation curve and XCT images of the reinforcement internal structure at multiple fiber volume fractions which are then converted into digital twins of the reinforcements. The virtual permeability of the reinforcement digital twin is computed through numerical flow simulations using realistic voxel models extracted from the stack of XCT images. The proposed approach has the capability of obtaining a plethora of information about the preform including, compaction response, statistical measurements of the internal preform geometry, and voxel models for numerical simulations. The methodology has been successfully demonstrated using two carbon fiber reinforcements with 3D woven architecture. The virtual permeability predictions were benchmarked against experimentally measured values, and were found to be in excellent agreement with the experimental data.