Influence of the outer skin on the flexural properties and thermal conductivity of densified Dendrocalamus asper bamboo

Abstract

In this work, the effect of densification and the maintenance of the outer skin on the flexural properties and thermal conductivity of Dendrocalamus asper Backer ex K.Heyne bamboo was investigated. The results showed improvements in bending resistance for the densified samples compared to the un-densified bamboo. Densified samples with the outer skin showed the highest bending strength. Samples with the outer culm wall in compression offered the best results, with an average modulus of rupture (MOR) of around 348.9 MPa and modulus of elasticity (MOE) of 28.4 GPa. These values are around 40% and 86% (MOR), and 17% and 30% (MOE) higher compared to densified samples without the skin and un-densified samples, respectively. The fracture sections of specimens after bending tests were analyzed using Scanning Electron Microscopy (SEM) to visualize crack propagation within the outer skin and bamboo tissues. Maintaining the skin increases the thermal conductivity, and the densified bamboo with the skin has a thermal conductivity of around 0.23 W/m.K, 12.8% higher than the densified bamboo without skin and 22.5% higher than un-densified bamboo. Although a reduction in thermal performance was achieved, it was concluded that is reasonable to keep the bamboo skin, as it improves the overall mechanical resistance and reduces material loss during bamboo processing.