Mode I cracking of three tropical species from Cameroon: the case of bilinga, dabema, and padouk wood
Résumé
This work aimed to study the initial stress to cracking of Cameroonian tropical woods. The forests of the Cameroonian part of the Congo Basin, abound in species highly sought after for structural applications. However, very little information is available on the Mode I cracking of these wood species. Specimens of sound wood from dabema (Piptadeniastrum africanum), padouk (Pterocarpus soyauxii Taub) and bilinga (Diderrichii nauclea) were produced. These specimens were subjected to three-point bending tests. Physical (density and moisture content), mechanical ($^{1/2}$ of elasticity, bending stress at break) and energetic (restitution rate and stress intensity factor) properties were determined. The results gave a restitution rate of 581 J/m² for dabema, 520 J/m² for bilinga and 202 J/m² for padouk, and a stress intensity factor of 0.98 MPa*$^{1/2}$mJ/m² for dabema, 1.28 MPa*m$^{1/2}$ for bilinga and 1.0 MPa*m$^{1/2}$ for padouk. It can be seen that dabema and bilinga are more resistant to crack propagation than padouk. On the other hand, bilinga and padouk absorb much more of the energy that causes micro cracks than dabema.