Digital Image Correlation System Application - Measuring Deformation and Load of Convertible Top Fabric 2010-01-0954

Strain gages have been widely used for measuring strain or deformation. They are very reliable and accurate. However, for application on fabric material, strain gages have their limitations.

In this paper, digital image correlation (DIC) is used to measure the deformation around the rear window on a convertible top. The test needed to be non destructive, the vehicle and convertible top could not be damaged. The deformation or strain measured on the fabric was used to estimate the force experienced at the interface between the glass and the fabric during an opening/closing application. A speckle pattern was created on the convertible fabric where deformation was to be measured with washable paint. The image of the measured area was first recorded. The convertible top was then latched down and the fabric was stretched. A second image was recorded again. Based on the two images, the deformation/strain between the two conditions was measured.

Convertible top fabric from a sample batch was cut into 50 × 200 mm coupon strips. Using a tensile test, a relationship between the applied force and the deformation on the strip was established. The relationship was used to estimate the force on the fabric over a 50 mm width.

The application and the difficulties encountered during the measurements are discussed in this paper. The specific numerical results are limited to this particular convertible top.