Reference object for traceability establishment in X-ray computed tomography measurements of fiber length in fiber-reinforced polymeric materials

X-ray computed tomography (CT) is an advanced non-destructive measuring technique that enables holistic three-dimensional measurements of outer as well as inner geometries and micro-scale features. In the field of fiber-reinforced polymeric (FRP) materials, CT can overcome the limitations of conventional methods typically based on time-consuming and destructive operations used for the measurement of fiber orientation and length, which are two characteristics that have a great impact on physical and mechanical properties of FRP parts. This work specifically addresses the CT measurement of fiber length, which is particularly complex because - differently from the fiber orientation analysis - it requires the individual fibers to be properly identified and segmented. Moreover, the traceability of such measurement has not been achieved yet. This work investigates an experimental methodology for traceability establishment and measurement uncertainty determination, based on the substitution approach. In particular, a task-specific reference object, including a selection of fibers with different lengths and configurations, was designed, manufactured and calibrated for the purpose.