Effect of slope of grain on mechanical properties of some tropical wood species

The aim of this work was to study the relationship between the mechanical properties of Cameroonian tropical woods and the slope of grain. The forests of the Cameroonian part of the Congo Basin abound in species that are highly solicited for structural applications. However, little information is available on the influence of the slope of a grain of these wood species. Clear wood specimens of ayous (Triplochiton scleroxylon), azobe (Lophira alata), fraké (Terminalia superbe), okan (Cylicodiscus gabunensis), padouk (Pterocarpus soyauxii), and sapelli (Entandrophragma cylindricum) were prepared. The specimens have a cross section of 20 × 30 mm and a length of 300 mm. These specimens were subjected to a four-point bending test and a double cantilever beam test. Modulus of elasticity (MOE), modulus of rupture (MOR), work at maximum load (WML) and fracture toughness (GIC) were determined. These mechanical properties were calculated for specimens with slopes of grain 0°,15°, 30°,45°,60°, 75° and 90°. The results showed that the slope of grain had significant effects on all the mechanical properties measured on clear wood specimens. MOE, MOR, WML, and GIC decreased with increasing grain slope. On the other hand, azobe and okan absorb much more of the energy that causes microcracking than the other species.