On the Bi-Axial In-Plane Behavior of Laminated Paperboard Components in Construction: A Representative Engineering Model

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. For example [TORRES et al., 2017] reports about concrete sand shortness and increasing cases of inter-continental sand shipping, since not every type of sand suits the requirements of concrete due to grain surface characteristics.

Wood is the main material for paper production. The wood fibers are connected to each other by resin and lignin. For paper production purposes this connection is broken either by mechanical or chemical processes and the cellulose fibers are mixed with water to a pulp mixture. For mechanical processing wood is broken down into wood chips before being ground.

Paper materials come with structural and production-related mechanical properties which can be advantageous or disadvantageous but mostly challenging in terms of using as construction material.

Paperboard laminates consist of single paperboard sheets flat laminated together, using an adhesive inter-layer. In contrast to fiber reinforced plastics like e.g. carbon fiber composites, where fibers are trapped in an epoxy resin matrix, paperboard laminates don’t consist of a matrix-fiber construct. Instead, the cellulose fibers of the paperboard sheets are connected to each other by hydrogen bonds. The in-plane structure of fiber reinforced plastics (FRP) composites possesses more distinctive principal directions with respect to paper materials, for which the distribution of fiber orientation can be idealized by an ellipse form. [GÖTZINGER, 2021] Despite structural differences, paperboard laminates and fiber reinforced composites exhibit similarities in their mechanical behavior.

Various case studies, concerning paper materials in construction, are presented and related to models and gained experiences from previous parts of this work. Experimental test results from student works are reviewed and taken further with use of those models and experiences. The span covers axial compression samples, bending beams and bolt connection of paperboard laminates.

In this final part of the present work, the gained experiences from previous parts of this work on paperboard laminates are transferred to a construction design process. First, an introducing part with an overview on the current challenging aspects on standardization in terms of building with paper are discussed. The focus is mainly set on the mechanical properties. Building physical design aspects like e.g. fire retardation, humidity and biological impact prevention etc. are not considered. The discussion of standardization challenges is followed by a general view on differences between current testing standards on mechanical properties of paper materials and of conventional construction materials. Further, decisive parts of Eurocode 3 as a current timber construction standard are taken into account and related to experiences with paperboard laminates. As a main part of the construction standards, the partial safety factors are introduced and a potential safety application method on the paperboard laminates for design purposes is suggested. Also, the corresponding laminate in-plane failure criterion is adapted. Further, a simplified criterion is suggested to enable easily accessible application possibilities. Finally, yield stress determination methods are presented as alternatives to the material strength values which were, used for establishing the in-plane failure criterion.

The present work has been dedicated to the development of an engineering model, representing the in-plane stress limits of paperboard laminates in order to be used for construction design purposes. On the basis of experimental and numerical investigations, the model has been validated and the application limits were addressed.