Innovative Ultra-light Structural Timber Sandwich Panels

Abstract

Sandwich panels are utilized extensively in many industries such as marine, aerospace, and automotive industries due to their high strength-to-weight and stiffness-to-weight ratios. However, sandwich panels have only just started to be utilized in the building industry. Most sandwich panels today consist of two thin and stiff skins and a low-strength foam core, which makes the panels vulnerable under bending action. Furthermore, with the recent global trend towards mid-rise to high-rise timber buildings, more attention is given to lightweight, cost-effective, and particularly sustainable wood products. This study aims to investigate the appropriateness of composite timber sandwich panels made by combining existing commercial wood products with affordable and sustainable local timber and wood waste, to manufacture sandwich panels for building purposes. These composite sandwich panels are manufactured by gluing commercial plywood skins to either bamboo rings to produce Bamboo Core Sandwich (BCS) panels or to peeler core rings to produce Peeler Core Sandwich (PCS) panels. In the first part of this thesis, a modified Ritz method is developed that can predict the flexural response of a sandwich panel with thick skins and thick-stiff core in one-way and two-way bending configurations. The proposed Ritz formulation is used to evaluate the flexural responses of the proposed BCS and PCS panels with different aspect ratios. To provide comparison, the results are compared with an engineered wood product, Cross-laminated Timber (CLT) panels with almost similar depths. A Finite Element Analysis (FEA) is then developed, validated against Ritz and previous experimental work, to capture the ultimate capacity and failure modes of the panels. In the second part of this thesis, the proposed panels are manufactured and physically tested in standard bending (using four-point) and shear (using three-point) tests. The optimum adhesive spread rate is identified through conducting shear bond tests. Results are compared to the test results of conventional CLT panels with almost similar depths. The experimental results are interpreted using analytical equations. In the third part of this thesis, single and double core layer BCS panels are manufactured and tested under axial compressive load. The capacity and failure modes of the BCS panels under combined bending and axial compression actions, are then investigated through validated numerical and simplified analytical approaches. Furthermore, a comparison is made between the axial compressive and combined compression and bending performances of the proposed BCS and conventional CLT panels.