Investigation of the Applicability of Fracture Mechanics for Tissue Paper

Sammanfattning: Tissue paper is a common type of paper material and is used in a variety of products. For tissue paper, several properties are of interest, such as absorbency, softness, bulk and mechanical properties. Embossing is an operation used to apply a pattern on tissue paper. It is used to improve several properties, but is known to reduce mechanical properties. Currently, no models can predict the loss of strength due to embossing. In this report base tissue paper is embossed with two different embossing patterns and tensile tests are conducted with and without edge notches. The edge notch length was varied between 0 mm to 12 mm. From the experiment, a modified Linear Elastic Fracture Mechanics model was applied on both base tissue paper and embossed tissue paper tensile test results. The experimental procedure is described. In total, four different paper qualities were tested. Two that are designed for toilet paper and two that are designed for kitchen paper. The tissue sheets were embossed using 3D-printed plates and conducted in a laboratory environment. Tensile tests with edge-notch specimens were performed. The notch lengths tested were between 0 mm and 12 mm long. It was investigated if any trends of the parameters in the model could be noticed due to embossing. The model worked well for all base tissue qualities. The embossing reduces the material's tensile strength compared to the base material. With increasing embossing load, longer notches are needed to drop the tensile strength of the specimen. Some general trends were noted. However, the impact of the embossing was different for different paper qualities and the embossing pattern used. The most significant difference between plates was noted in specimens with high embossing load. With increasing embossing load, the edge-notch must also be longer to reduce tensile strength. The model parameters changed more for machine direction (MD) specimens than crossmachine direction (CD) specimens.