Comparative Analysis of the Moisture Content and Density on Bending Strength of Azadirachta indica and Siamea senna in Steam Cold Method

Abstract

This study investigated the steam and cold bending strength of sapwood and heartwood from two underutilised timber species, Azadirachta indica (Neem) and Senna siamea (Cassia), to evaluate their viability as alternatives to conventional species such as Khaya ivorensis (African Mahogany) in the furniture and joinery industries. The physical characteristics, including moisture content and basic density, were evaluated according to the EN 13183-1 (2002) and ISO 3131 (1975) standards. The bending characteristics were assessed using the form tool method at both cold and steam temperatures. Descriptive statistics revealed significant variability among the species and wood segments. Neem sapwood revealed the highest moisture content at 88.15%, whilst Cassia heartwood displayed the lowest at 47.50%. The density analysis indicated that Cassia heartwood displayed the highest basic density at 898 kg/m³, whereas Neem sapwood registered the lowest at 674.61 kg/m³. Mixed ANOVA demonstrated statistically significant variations in density and moisture content (F=44.073, p<0.05), with pairwise comparisons revealing significant differences among most group pairs, except for the comparison between Neem heartwood and Cassia sapwood. Bending studies demonstrated that Cassia heartwood displayed exceptional performance in both cold and steam bending, achieving up to 85% undamaged samples during steam bending, therefore categorising it in Quality Class I. Neem sapwood exhibited superior performance relative to heartwood in steam bending, classifying it in Quality Class II. A direct correlation between wood density and bending strength was noted, as demonstrated by the elevated density and enhanced bending performance of Cassia heartwood in both cold and steam treatments. The study revealed a favourable correlation between wood density and bending quality. This study advocates for the utilisation of Cassia and Neem as sustainable alternatives to traditionally harvested species, contributing to forest conservation efforts in Ghana.