Fiber misalignment analysis in PCM-UD composite materials by Full Field Nodal Method

Abstract

In this work, a new full-field and non-destructive methodology for measuring process-induced fiber waviness in composites are presented, benchmarked, and successfully applied to predict long fiber-reinforced stiffness composite laminates. The proposed method, named the ''Full Field Nodal Method'' (FFNM), computes the misalignment angle by interpolating the displacement measured on a discrete set of sampling points. Sampling points have been traced on the prepreg surface before curing, and bilinear Lagrangian interpolating functions have been adopted and compared. Several samples, made with compression molded prepreg, have been used to test the new method capabilities in this work. A first benchmark was done measuring the fiber waviness on samples through the new method and by another one recently presented in the literature. Average fiber angles predicted by the FFNM, with bilinear interpolating functions, were in high agreement with experimental results. Fiber angle misalignment measured by FFNM was used to orientate the reference system of elements of the FEA model. Numerical results in terms of stiffness and strain field were compared to those detected by the Digital Image Correlation technique (DIC) during the tensile tests. Comparison of numerical and experimental results showed an excellent prediction of material stiffness and the strain field with an error of 15%.

Keywords

• Fabrics/textiles
• Defects
• Elastic properties
• Finite Element Analysis (FEA)
• Non-destructive testing
• Optical microscopy