Novel metric “Implenarity” for characterization of shape and defectiveness: The case of CFRP hole quality

Image Processing is rapidly expanding as a technique for object and defect analysis because of the high ease of its coupling to automation and IT solutions. Yet, issues with transferability of the measurement approaches and metrics currently used in mechanical systems often remain unsolved. Study reports on the developed approach for shape and defectiveness characterization by combining Delaunay triangulation of object's contour with uniformity analysis of triangles in the generated mesh using developed metric “Implenarity”. When analyzing hole drilling in CFRP, experimental validation found that for highest quality of CFRP holes, implenarity shifts from its maximum of I = 0.22 for a circle to I ≈ 0.16 for microdefects below 100 µm—normally not quantifiable with conventional techniques. In presence of larger hole defects, implenarity demonstrated similar capabilities to standard metrics, but avoided their inherent flaws. Implenarity continued distinguishing degree of defectiveness for the same area of uncut fibers (F_a-cov) and the same delamination diameter (F_d,F_da).