Quantitative determination of morphological features of triaxially braidedcomposites by the use of machine vision

The morphologies of the reinforcement strongly influence the material prope rties of fiber-reinforced composites. The ability to quantify the morpholog ical features of the composites is important for the prediction of material properties and for quality control of the manufacturing processes. This pa per presents a method for quantitatively measuring fiber braid angles at th e surface of a part by the use of computer-aided image-processing analysis. The materials under investigation are triaxially braided glass/urethane co mposites. The determination of braid angle at a sample surface is performed non-destructively and is based on the use of a standard fast Fourier trans form (FFT) method coupled with a novel directional scanning method develope d as part of this work. Calibration tests were performed for the purpose of comparison between computer-based pattern recognition and manual determina tions. Good agreement between machine vision results and manual measurement s for braid angle was found. The machine vision system is fully automated a nd features rapid image acquisition and processing with good measurement ac curacy. It can be applied to on-line quantitative measurements of geometric al features and other applications that are important for quality control a nd engineering design. (C) 2000 Elsevier Science Ltd. All rights reserved.