Non-contact measurement of local grammage and mechanical material properties

Abstract

A new method that provides a measure of local grammage and makes it possible to study local mechanical stiffness properties of sheet materials is presented. The measurement is achieved without any mechanical contact with the material and the spatial resolution can be chosen in the interval 1 - 100 . The method is based on the use of a high-power pulsed KrF excimer laser which generates a pressure pulse and thus creates a local deformation of the sheet. An optical interferometer is used to detect the deformation of the material over time. From the time-resolved interferometer signal, the desired output values for the grammage and mechanical stiffness can be extracted. The method is applicable to sheet materials such as paper and plastic films. Experimental results obtained from measurements on Mylar polyester films show that it is possible to attain a high reproducibility when measuring the grammage and that it is possible to resolve a small relative change in the elastic modulus.