Identification and Quantification of 3D Fiber Clusters in Fiber-Reinforced Composite Materials

Microscale computed tomography scans of fiber-reinforced composites reveal that fibers are most often not strictly parallel to each other but exhibit varying degrees of misalignment and entanglement. One characteristic of this entanglement is the degree to which fibers stay together as clusters. In this study, a method for identifying and isolating fiber clusters was established, and scans of two different composite microstructures were analyzed. To identify clusters, fiber center points of the first cross-section were triangulated, and the variation of the perimeter and area of triangles along the fiber direction was used to identify fiber triads which stay together. A filtering process eliminated fiber triads not part of a larger cluster. Geometric properties of the clusters such as cluster orientation, radius of gyration, cluster density, and volume fraction were calculated and compared. The metrics revealed fundamental differences between the two samples, suggesting that clusters have origins in manufacturing.