Reflectivity characterization of thermoplastic composite tapes for automated fiber placement: A rapid measurement technique

This study proposes a fast camera-based measurement to characterize the directional reflectivity of a fiber-reinforced thermoplastic composite tape. The method has potential use cases for measurement of within-batch and batch-to-batch material variations for laser-assisted automated fiber placement, and is able to identify differences in the consolidation state of a material. The acquired reflectivity patterns are parameterized using a bi-directional reflectance distribution function. The facet orientation distribution assumed in this bi-directional reflectance distribution is compared to measured facet orientation distributions derived from height measurements, providing insight in the accuracy of the assumed distribution. As an application, the reflectivity measurement is applied to specimens on as-received tapes and specimens after in-situ consolidation during automated fiber placement. The reflectivity measurement is sufficiently accurate to capture significant differences in the reflectivity pattern based on the consolidation state of a thermoplastic composite tape. The current methodology acquires information on the directional reflectivity in a tenth of a second, offering potential for acquiring large quantities of data as part of an off-line or in-line inspection system.