From measurements errors to a new strain gauge design for composite materials

Significant over-prediction of the material stiffness in the order of 1-10% for polymer based composites has been experimentally observed and numerical determined when using strain gauges for strain measurements instead of non-contact methods such as digital image correlation or less stiff methods such as clip-on extensometers. In the present work, this has been quantified through a numerical study for three different strain gauges. In addition, a significant effect of a thin polymer coating or biaxial layer in the erroneous using strain gauges has been observed. An erroneous which can be significantly decreased using an enhanced grid design of the measuring grid.