Experimental and numerical assessment of a cross-insulated timber panel solution

Abstract This paper presents an experimental and numerical study about the flexural and compressive behaviour of a novel type of sandwich panel solution based on Cross-Laminated Timber (CLT). The layout of the new panel, named Cross-Insulated Timber (CIT), is similar to the one of a five-layer (CLT) panel, but the inner layer is made of polyurethane rigid foam instead of timber as in Structural Insulated Panels (SIP), aiming to rationalize the wood volume and combine it with a low-density core layer for improved thermal insulation and reduced weight. The study about the mechanical behaviour of CIT included the variation of the layers' thicknesses, in order to assess their influence in the mechanical behaviour and also the suitability of the numerical models to describe such behaviour. The experimental campaign included bending tests and axial compression tests in full-scale CIT beams (only one lamella at the external layers) and panels (multiple lamellas at the external layers) and SIP beams, which allowed assessing their global stiffness, resistance, buckling behaviour and failure modes. In bending, both CIT and SIP presented non-linear behaviour, due to the polymeric foam core, and their load capacity was governed by the shear failure of the core, which was the dominant failure mechanism. For the bending tests, the Timoshenko and Kreuzinger analytical models described quite well the deflection observed in the linear range, while for the non-linear branch of the load-displacement curves, the developed finite element model provided good accuracy. The Euler’s buckling load formula adapted for sandwich panels predicted quite well the buckling load measured in the compression tests. The results showed the potential of the CIT solution for structural applications and of the analytical and numerical models for design purposes.