Improving precision in the cavity thickness measurement for fabric compaction

Abstract. As seen in the first international compressibility benchmark, inaccuracies in the fabric stack thickness measurement, the approach to compliance correction and the non-parallelism between compaction plates resulted in highly inaccurate compression curves. The factors influencing the accuracy of thickness measurements in compaction tests were studied to provide a comprehensive guidance and measurement recommendations to improve upon the current procedures and enhance the accuracy of thickness measurements. These include the variability in the direct thickness measurements due to accuracy of the laser sensors measurements and the variability in the machine compliance measurements. In conclusion, while both thickness measurement methods yielded comparable results, it is noteworthy that the direct method exhibited greater variability in thickness measurements compared to the indirect method, which rely on the machine displacement. Minor changes in the rig's displacement or in the orientations between compaction plates due to differences in the pressure distribution during compaction, combined with other sources of variability such as external interferences or vibrations from the compaction plate led to variations in measurement´s accuracy throughout the tests.