In the Värmland region, Sweden, an innovative sandwich structural element has been designed by the cooperation of pulp and paper companies for possible use in indoor products, such as tables, shelves, doors, and furniture in general [1]. The element, lightweight and strong, has facesheets of laminated paperboards made of recycled and/or virgin wood fibres. The core, made of paper pulp, has a unique shape like a cup box with staggered positions between the cups, see [1]). At the Department of Engineering and Chemical Science at Karlstad University, the mechanical performance and properties of the elements have been investigated via experimental tests and finite element (FE) models for different applications. Recently, four-point bending tests have been conducted in sandwich beams from the element, see Fig. 1(a). The facesheets of the beams were made of virgin and/or hybrid (virgin + recycled fibres) paper materials. Results from quasistatic experimental tests were evaluated by means of digital image correlation technique for accurate measurements of the beam deflection.

In this presentation, we will address aspects of flexural and shear rigidities of the tested samples [2, 3], as well as main observations of failures, which occurred at the top facesheets (c.f. Fig 1(b)). A parametric FE model will also be presented along with its calibration, capability of predicting the failure (c.f. Fig 1(c)), and possibilities for structural optimization.

References

[1]    Ecopals AB, Hållbar möblekonstruktion till en bråkdel av vikten/Durable furniture construction at a fraction of the weight. Retrieved March 03, 2024, https://ecopals.se/

[2]    Howard, G.A., Analysis and design of structural sandwich panels, Pergamon, (1969)

[3]    Lorna, J.G., Michael, F.A., The design of sandwich panels with foam cores. In: Cellular Solids: Structure and Properties. Cambridge University Press, 345-386, (1997)