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An Optical Method to Measure the Bending Stiffness of Fabrics

Christian Indra

Christian Indra

More and more modern technologies are used for designing clothes and garments. One of these technologies is simulation of clothes. For
simulation some mechanical parameters like Young's-modulus, shear-modulus, bending stiffness, etc. are needed. Especially the measurement of the bending stiffness of the garments can be expensive, because a high precision measurement setup is needed to determine the typically small bending stiffnesses of cloth.
In this master thesis some novel methods are analyzed, determined how they perform and the best is selected.
The main approach to do this measurement is by using digital image analysis. Figure 1 shows the developed device that is used to determine the bending stiffness. The fabric under test is bent just by its own weight and is placed on the groundplane of the device.
It uses triangulation to determine the defection line from the taken camera image shown in Figure 2. With the methods of digital image analysis the deflection line is calculated and thus the bending stiffness is determined. For a fabric width of 10cm the bending stiffness that can be measured ranges from 10nNm² to 100µNm².

Figure 1: Device to measure a fabric placed on the ground plane. Camera and laser used for triangulation are mounted on the optical bench.

Figure 1: Device to measure a fabric placed on the ground plane. Camera and laser used for triangulation are mounted on the optical bench.

Figure 2: Measurement of the bending sitffness using triangulation.

Figure 2: Measurement of the bending sitffness using triangulation.

Keywords: garments, fabrics, light section, triangulation, beam theory, Euler-Bernoulli-Theory

August 27th, 2016