Speaker
Description
The function of paper has expanded considerably beyond its original role as a pure information carrier. Paper is now used in a wide range of modern applications, including packaging, furniture and insulation materials. As a result, paper has established itself as a sustainable alternative to carbon-based materials in a variety of areas.
Despite the high demand for paper and paperboard across various sectors, there is still a lack of understanding regarding their macroscopic behavior. The microscopic phenomena that lead to macroscopic plasticity and damage, as well as the means of enhancing material properties for specific loading conditions, remain unresolved. It is therefore crucial to gain a comprehensive understanding of the microstructural mechanisms that influence macroscopic properties.
To gain this understanding, a synthetic fiber network was developed within the finite element framework. The fiber network was generated by a virtual compression process, which was carried out in analogy to the manufacturing process of paper. Contact surfaces were represented using a cohesive contact formulation that permitted fiber separation. The corresponding contact properties were calibrated based on experimental tests of single fiber-fiber bonds. In addition, the distribution of fiber orientation within the network was considered, as this significantly affects the anisotropy of paper at the macro level. Micro-CT scans revealed that fiber orientation is predominantly in-plane. Probability density functions were identified that effectively approximate the distribution of fiber orientations. Incorporating these PDFs into the network generation process improved the representation of the numerical microstructures. As a result, network models were created that integrated various features, including single-fiber anisotropy due to microfibrils and separating contact surfaces. Thereby, we considered essential structural characteristics including paper thickness, basis weight, and fiber orientation.
The response of the bulk material was determined by performing virtual tensile tests on the synthetic fiber networks. The synthetic networks were able to mimic the anisotropic behavior of paper and demonstrate the influence of fiber orientation on mechanical properties. In particular, it was observed that the modulus of elasticity of the paper sample increased with increasing fiber orientation.
