Customized papers: Understanding and adjusting morphology and topology
Motivation and objective of subproject 1
Papers specifically designed and manufactured for building applications are only used to a very limited extent. Currently, papers for building applications, such as plasterboard or honeycomb panels, are made from recycled fibre. Commonly used packaging applications such as customary liners or test liners are not or only slightly optimized for applications in construction with regard to fibre properties and sheet build-up. Up to now, the potential of paper as a building material is therefore not exploited. This applies both to the mechanical properties such as the load-bearing arrangement of the fibres as well as to functional properties such as moisture resistance and flame-retardant properties. Today, papers are characterized using methods and parameters that are not sufficient for the design of components and structures and not applicable for design and modelling methods. These gaps will be overcome within the scope of this subproject and papers optimized for construction applications will be produced and characterized.
Methods for the characterization of the papers and further development of the test methods
The paper materials are characterized by papermaking test methods, whereby the mechanical properties are of primary importance. On the one hand, these measurements help to understand and optimize the processes of paper production. On the other hand, the material properties are incorporated into the modelling of the forming processes (subproject 4) and the structural analysis (subproject 5). The characterization methods are extended in such a way that the material properties obtained can be used for the modelling of the forming processes, the structure analysis and the component design. In particular, the boundary conditions and the test parameters for the measurement methods are to be adapted.
Material development for isotropic papers for construction applications
For paper- or plate-shaped components, papers with predominantly isotropic strength properties in the sheet plane are required. The first investigations for the production of components (subproject 4) and assemblies (subproject 5) will show which parameters have to be optimized for this application. From a current point of view, high stiffness and high elasticity are required in addition to a high breaking strength. Within the scope of this work package, the aforementioned properties of papers are developed in the laboratory scale in such a way that the requirements for the planned components and assemblies are achieved. Model-based empirical work is carried out. In order to achieve high stiffness, multilayer sheet structures are also suitable. In order to be able to produce semi-finished products on a larger scale for the production of components and subassemblies, a paper machine (paper width approximately 30 cm) is available at TU Darmstadt – PMV.
Material development for papers for building applications with high-grade fibre orientation
For bar-shaped components, papers with the highest possible tensile strength in the longitudinal direction of the bar are required. The targeted orientation of the fibers in the sheet can make a significant contribution. On conventional paper machines, an influencing of the fiber orientation is possible, but only to a limited extent. For the production of highly unidirectionally oriented papers, a test rig on laboratory scale is currently built based on the work of Kortschot. This test rig is developed in such a way that a higher fibre orientation and thereby a considerably higher relative tensile stiffness in the longitudinal direction is possible. The potential of unidirectionally orientated papers will be demonstrated and the link between the degree of orientation and the strength values can be determined.
Recyclability of components and assemblies
Components made of paper and paper composite material should be designed in such a way that the material can be recycled at the end of the building's use. Methods for determining the recyclability of papers are developed at the PMV. These methods are transferred to the components and assemblies developed within the BAMP project. The main issues are to ensure the separability of paper and other materials (metal, plastic), to find suitable processes and process conditions for the defibration of the paper components while overcoming the difficulties arising from the chemical functionalization of the paper fibres to increase the wet strength. The investigations on the recyclability are carried out using the components and assemblies elaborated in subprojects 4 and 6. The results flow back to these subprojects so that, if necessary, manufacturing and design can be improved in terms of recyclability.