Accuracy of fiber length measurements using X-ray computed tomography for the analysis of composite materials

X-ray computed tomography is capable of measuring non-destructively the fiber geometrical characteristics that deeply affect both physical and mechanical properties of fiber-reinforced polymeric products. In particular, X-ray computed tomography can overcome the limitations of conventional methods used for fiber orientation analysis and fiber length measurement, which are mainly based on time-consuming and destructive optical analyses. This work especially addresses the case of fiber length measurement, which is particularly complex because – differently from the case of fiber orientation and concentration analyses – it needs the individual fibers to be identified and segmented. Moreover, the accuracy of such measurements has not been thoroughly investigated so far. In this work, a new method for accuracy evaluation is proposed. The method is based on the use of a newly developed task-specific reference object, which has been designed, manufactured and calibrated with respect to the length of a selection of fibers with different lengths and different configurations.