Partial volume correction for approximating crack opening displacements in CFRP material obtained from micro-focus X-ray CT scans

This paper presents a partial volume correction technique that applies a measurement weighting based on grey scale intensity values, allowing crack opening displacements (CODs) to be better estimated in micro-focus computed tomography (μCT) scans. These were tested on 3D data obtained from two separate μCT scanners on particle toughened and non-particle toughened carbon fibre material subjected to low velocity impact. Direct comparisons of COD estimations were made with higher resolution measurements obtained using synchrotron radiation computed tomography (SRCT) scans taken at the European Synchrotron Radiation Facility (ESRF). In this study, partial volume correction is reported to improve the accuracy of these measurements to within 20% of SRCT measurements, whereas measurements based on counting interconnected voxels representing a detectable crack are reported to consistently overestimate crack openings by up to 500%. Scatter in estimations was dependent on material type, noise, and artefacts associated with μCT volumes.