Bøger af Francisco Antonio Rocco Lahr

Wood-based panels have been widely used around the world, replacing solid wood in various segments of the industry, such as furniture, panels, structures and other building components. The large volume of waste generated by agro industry enables the development of alternative and sustainable materials, highlighting the particleboard. This paper presents a study about production and evaluation of particleboard of Eucalyptus grandis and oat hulls, bonded under pressure with two types of resins (polyurethane based on castor oil and urea formaldehyde). Physical-mechanical performance of the panels produced was evaluated based on ABNT NBR 14810:2006, ANSI A208.1: 1999, BS EN 312: 2003 and CS 236-66: 1968. A variance analysis (ANOVA) evaluated the factors influence: Eucalyptus grandis, with mass ratios of 70, 85 and 100%; oat hulls, in proportions of 15, 30 and 100%; adhesives, in proportions of 10, 12 and 14%, and the combination of both, in each of the response variables (physical and mechanical properties) evaluated. Results showed good physical-mechanical properties, in some cases much higher than national and international codes requirements.

The purpose of present study was to create a theoretical model that allowed with security and reliability to obtain, values of strength and stiffness to which the structural element will be submitted throughout its useful life. The effect was studied for strength and stiffness properties, and the modulus of elasticity (EM) and bending strength (fM) were evaluated according to the increasing number of cycles of the fatigue test for the five classes of hardwoods, recommended by NBR 7190 (1997). These results allowed to construct a fatigue curve, relating the two variables as a function of the number of cycles (Nc) - construction of the curves EM x Nc and fM x Nc. The fatigue effect was present and pronounced in all strength classes. A reduction in strength and stiffness properties was observed with increasing loading Nc applied at all frequencies. From the multivariate regression models and the respective determination coefficients, a generic model was obtained for the set involving the five wood species, emphasizing the insertion of the apparent density as an independent variable, which allowed a greater generalization of the use of the adjustments in the estimation of properties.