Compressive stress–strain behavior of paper material affected by the actual contact area DOI 10.14622/JPMTR-1911

Abstract

The surface topography plays a very important role in the mechanical behavior of paper materials, especially for the compressive properties of thin sheet. When the surface of the cylindrical indenter is very smooth, the actual contact area under force is usually much smaller than the nominal contact area because of the surface roughness of the paper. This paper shows a method for measuring the actual contact area; with the aid of a microscope, a new approach based on image processing technique is presented to calculate the relationship between force and actual contact area. With the help of this method, the actual pressure–deformation relation and the actual modulus of paper could also be calculated. The calculation results show that there is an obvious difference between the results calculated by actual and nominal contact area. The varied trend and the values of the actual modulus are also obtained; at the beginning of the loading the actual modulus is decreasing and then close to a constant value. The universal testing machine Zwick Z050 and the optical surface topography measuring machine Sensofar Plu Neox were employed to determine not only the strength and deformation performance but also the surface roughness of specimen. Based on the obtained results the influence of carbon paper on the compressive behavior of copy paper is further discussed from different standpoints. The numerical results demonstrate the feasibility and effectiveness of the new method.