Influence of growth rings on the mechanical properties of Pinus wood

Visual inspection is the first parameter of the quality of materials, especially when it comes to wood, which has natural defects, such as Pinus wood. This study aimed to evaluate the relationship between the growth rings and the physical-mechanical characteristics of the Loblolly and Slash pine wood. 250 wooden specimens were used, with dimensions of approximately 89 mm(3) x 39 mm(3) x 90 mm(3). To determine the proportion of the area and thickness of the latewood in the growth rings, the faces of the specimens were scanned, and the proportion of the area of the latewood/earlywood was quantified by means of analyzer software. The specimens were separated by the number of growth rings and their form of presentation in the transversal plane, totaling five treatments. Then, tests of compression perpendicular to grain were carried out using four different methods (ABNT - F-c,F- 90, ISO - F-c,F- 90, ASTM - F-c,F- 90, ABNT- E-c,E- 90). As a result, a significant difference was found between the means of the five treatments used for compression perpendicular to grain. The mathematical models found were less fit. In conclusion, the apparent wood density was explained, in part, by the number of years of growth, as well as the proportion and thickness of the latewood. The normal compressive strength of the fibers showed a significant difference between the ISO 13910, NBR 7190, and ASTM D143 standards.