Digital Image Correlation Method for Determining the Poisson's Ratio of Knitted Fabrics

In order to solve the problem that the traditional method for determining Poisson's ratio is not applicable to fabrics, this paper combines digital image correlation method to perform uniaxial tensile test on knitted fabrics, thus proposing a method to determine Poisson's ratio under large deformation with the whole specimen as the research object. The experiment employed 6 different knitted fabrics, including weft plain and net structure. Firstly, the whole process of uniaxial stretching was recorded. Secondly, displacement analysis was performed for each frame with a digital image correlation method in Matlab. After, the feasibility of the experiment was verified by t-test between the calculated value and the actual tensile value. Finally, the Poisson's ratio values were calculated, which were in normal range. This method avoided the problem of fabric necking and improved the accuracy by extracting 30 pictures per second. The experiment proved that the method is suitable for both weft plain and net structure, which provided a new idea for the study of Poisson's ratio of knitted fabrics.