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The Cameroon has two bamboo species indigenous to Africa (the alpine bamboo, Yushina alpina and the savannah bamboo, Oxytenanthera abyssinica), and one largely exotic species, Bambusa vulgaris. However, little on their physical characteristics and strength for the composites materials applications is known for these two indigenous bamboos species in Cameroon. Therefore, in this study, emphasis was laid on the alpine bamboo Y. alpina, to evaluate its potential for biocomposites applications. Y. alpina with ages ranging from 1 to 3 years, 4–5 years, and 7 years were characterized. The mechanical and physical properties of these three age ranges were compared. In the first place, the surface texture of the fibers was examined by scanning electron microscopy. Afterwards, chemical treatment was performed on the fibers with 1 % NaOH. In addition, the chemical bonds of the molecules (functional groups) were identified by Fourier transform infrared spectra (FTIR) and the thermal properties of the fibers were examined with a thermogravimetric analyzer. Furthermore, the fibers density was assessed using the Rilem protocol and a tensile testing machine was used to determine the mechanical properties of the treated fibers with 1 % of NaOH. Finally, a dynamic mechanical analysis of 7-year-old Y. alpina fibers was carry out. The results indicate that the Young's modulus of treated fibers with ages ranging from 1 to 3 years, 4–5 years, and 7 years were around 18 GPa, 10 GPa, and 14 GPa, respectively. In summary, this study underlines two primary points: (1) providing a platform for researchers to better understand the influence of age on the physical and mechanical properties of indigenous bamboo Y. alpina; and (2) providing a platform to validate suitable designs of biocomposites materials with Y. alpina.

This paper aims to study the mechanical behavior and surface chemistry in relationship with moisture content of Iroko (Milicia excelsa), Bilinga (Nauclea diderrichii), and Tali (Erythrophleum suaveolens). Mechanical characterization was done experimentally using tensile and bending tests. Chemical semi quantitative analysis of the wood at 10%, 15%, 20% and 30% of moisture content was investigated using attenuated total reflectance Fourier transform infrared spectroscopy. The main chemical functions involved by the presence of water were identified as well as the other functional groups. The ratio between lignin and carbohydrates was estimated for all the wood species. The results indicated a negative correlation in the relation between moisture content and mechanical properties. Tali had the higher bending strength while Iroko had the lowest value. The average percentage change rate of the Young’s moduli induced by 1% of moisture content changes, especially between 10% and 20%, varied with the wood species: 1.69% in Tali, 1.65% in Bilinga and 2.54% in Iroko approximately. The infrared spectra obtained differed among species. The results also showed that Iroko contained higher lignin and were the least sustainable according to mechanical properties. The bands at 3340 cm−1 and 1635 cm−1 were more impacted by moisture content. Keywords: Tropical wood, Chemical component, Strength, Moisture content, ATR-FTIR

In order to reduce the heat and mass transfers in buildings, which increase energy bills, the development of composites materials such as earth bricks stabilized with thatch fibers is important for their construction. This paper aims to study a one-dimensional model of heat and moisture transfer through porous building materials. The coupled phenomena of heat and mass transfer are described by the Luikov model. Equations and boundary conditions are discretized using the finite difference method. The results obtained illustrate the temporal evolutions of the temperature and the moisture content, as well as the distributions of the temperature and moisture content inside the wall. The profile of the temperature and water content that are obtained are compared with the other numerical solutions that are available in the literature.