///PhD: On the Bi-Axial In-Plane Behavior of Laminated Paperboard Components in Construction – A Representative Engineering Model by Nihat Kiziltoprak
The modern building industry demands for alternative construction materials due to shortage and thereby also expensiveness of classical building materials and also ecological aspects, which gained high global popularity within the last decades. Paper materials are widely used in various industry fields and everyday life for centuries. Within the concept of renewable wood, paper materials also attract the modern society and covers thereby preferred ecological aspects. Paper materials also provide recyclable construction. Above all, many of the paper-based components like e.g. corrugated cardboard, honeycomb-plates, wound tubes, edge protectors from the packaging and shipping industry are implemented in modern day paper building projects due to their structural efficiency. Especially for high strength and stiffness performances at low weights, paper materials develop a great potential. Furthermore, projects by the Japanese architect Shigeru Ban attracted interest of a wide audience to building with paper materials since 1990s. Realized projects confirm the feasibility of paper-based structures for long-term use.
The general objective of the present work is to characterize the material behavior of laminates made of paperboard layers for use in structural engineering and to offer a model for application in design processes. For this purpose, extensive experimental investigations are carried out on laminates for both in-plane and perpendicular to plane loading behavior. Based on the results from the experimental investigations, engineering models are established to represent the material behavior. Simplifications of the Tsai-Wu failure criterion are made via corresponding parameters to represent the in-plane bi-axial strength hypothesis of the investigated laminates with strength values obtained from uni-axial tension and compression tests. In addition, the model is modified to offer a high safety level in the normal/shear stress interaction.
The established model is fed into a numerical simulation environment and its suitability for the present paperboard laminate is presented using validation tests. Additionally, case studies are presented in which the collected knowledge and the built engineering model are applied. In a further step, analytical models are presented through which the compressive strength of the laminates can be predicted based on the properties of the individual component layers. The models are based on equilibrium conditions and energy equations which, among other things, take into account shear effects occurring between the individual layers. Finally, testing and design standards are discussed, which do not exist for paper materials in the form known for conventional building materials from construction standards. Based on the established engineering model, a design approach of the laminate for ultimate load calculations in structural engineering is derived. The focus is on a balance between safety, economic efficiency and ecological justifiability.
Defense date: 04.07.2022! Book to come!