Scatter of mechanical properties of 2D biaxial and triaxial braided reinforced composites and their correlation with visual features.

Tensile properties of 2D braid reinforced composites are analyzed with regards to process-induced fiber architecture variations. First, a parametric study concerning the effect of radial braiding parameters on the braid characteristics is performed and a quantitative quality index based on visual attributes is introduced. Second, test laminates are produced with vacuum resin infusion to conduct tensile tests with biaxial and triaxial braids of varying qualities. To correlate fiber architecture variations with mechanical properties, each braided layer is scanned and analyzed by means of gray scale based image processing. This allows for determining specimen-specific fiber orientations and correlating them with mechanical properties. The results show strong correlations of measured fiber architectures and mechanical properties. Thus, the study suggests that detailed information about the (local) fiber architecture should allow for significantly improving the prediction of 2D braided composite properties. [Display omitted] • Distance between braiding ring and mandrel has a strong influence on braid quality. • Tensile strength scattering strongly correlates with fiber angle variations. • Triaxial braids are more affected by fiber architecture variations than biaxial ones. • Elongation at break is higher for homogeneous braids than for inhomogeneous braids. [ABSTRACT FROM AUTHOR]