Effect of wood grading on the mechanical properties of glulam made of Tectona grandis

Abstract

This study aimed to evaluate the influence of the wood grading by the method of stress waves in the mechanical properties of glued laminated beams (glulam) made of Tectona grandis. A total of 87 battens with dimensions of 25 x 75 x 3.000mm were obtained from the 5 trees and 3 logs per tree, in the axial direction (base, middle and top) and radial (pith - bark). After drying, the battens were planed to the final dimensions of 20 x 60 x 2200mm, and then subjected to grading by application of stress waves. Were defined three classes of dynamic modulus of elasticity (DMOE) and the beams were composed with five pre-classified battens. The beams were bonded with resorcinol-phenol-formaldehyde resin, with a weight of 350g / m2(double surface), specific pressure of 1.0 MPa and pressing time of 8 hours. The grading process of the battens using the stress wave method showed to be efficient for the composition of beams. The results of static bend and glue line shear strength tests indicated the technical feasibility of using wood of Tectona grandis for the production of glued laminated beams.