Experimental studies on fiber cement boards under compression loading

Fibre cement boards are widely used as external cladding in cold-formed steel (CFS) building systems, due to their superior durability and weather-resistant characteristics. These boards are made of cement and reinforced with short, randomly oriented, non-hazardous cellulose fibres. Characterizing the observed stress-strain behaviour of the board under compression loading is a challenging task due to: a) loading eccentricity which induces bending, b) global buckling caused by high slenderness of the specimen, and c) stress concentrations at the loading end resulting in bearing failure. The above failures are usually handled at the specimen preparation stage by gluing additional numbers of boards to reduce slenderness, and by the inclusion of end tabs to avoid bearing failure. However, the introduction of glue in the board specimen may alter the strength characteristics and modify the load transfer path. Preliminary studies on the board specimens following the standard testing procedure (ASTM D3501) for wood-based panels fail to simulate the real material behaviour of the boards under compression loading. It is clear that the existing test methods have several shortcomings and hence cannot be adopted for fibre cement boards. In this paper, the fibre cement boards were tested under compression loading using combined loading compression (CLC) test fixture. This paper presents the details of the experimental study and the results for board of thicknesses 8, 10, and 12 mm, respectively. The test matrix includes specimens tested in both longitudinal and transverse directions. Under compression loading, the board exhibited nonlinear behaviour up to failure. The structural parameters like ultimate stress, ultimate strain, Young's modulus, and Poisson ratio in both longitudinal and transverse directions were obtained. This study proposes a nonlinear constitutive model for the board material.