Wood toughness is a mechanical property of interest in structural design where the load impact must be considered, finding a strong application in bridges, however, not an integral part of the mechanical properties commonly investigated in the characterization of this material. This study aimed to investigate with the aid of variance analysis, the influence of growth ring orientation to obtain toughness for Angelim Saia (Parkia pendula), Eucalyptus grandis, Pinus elliottii and Corymbia citriodora wood species, considering three different positions, so that the orientation causes tensile strength in fibers near the pitch, near the bark, and in the radial direction. The results of the statistical analysis revealed that there was no significance in the orientation of the growth rings to obtain the toughness of the wood species investigated, where the highest values were for Corymbia citriodora and the least values were for Pinus elliottii.
This study aimed to demonstrate the feasibility of obtaining wood-polymer composites (WPC) displaying a performance superior to that of untreated wood from reforested genera. To this end, wood samples of Pine (Pinus caribaea) and Eucalyptus (Eucalyptus grandis), whose density is compatible with this process, were impregnated with the polymeric monomers styrene and methyl methacrylate, using benzoyl peroxide to initiate the polymerization process forming free radicals. The vacuum-pressure method was used to impregnate the samples with monomer-initiator solution. The results indicated a significant improvement of all the properties investigated, including dimensional stability, for the Pine-WPC, while Eucalyptus-WPC, owing to the wood's low permeability, showed only increased values of hardness parallel and perpendicular to grain
Wood often exhibits different behavior, depending on the kind of acting forces. GeneraIly, wood can resist greater solicitations if short time intervals are considered. The mechanical property involved in these cases is the touglmess, which values are determined in impact bending tests. Several basic uses of timber depend on the touglmess, property not widely studied to tropical species grown in Brazil. This work, conducted in Wood and Timber Structures Laboratory (LaMEM), Department of Structural Engineering (SET), São Carlos Engineering School (EESC), São Paulo University (USP), aims to: a. determine the relation between touglmess and wood density at 12% of moisture; b. determine the relation between toughness and moisture content (O -30%). In order to reach the first object, experimental results related to thirty six tropical species (density range 0,55 -1,05 g/cm3) were considered, no less than twelve specimens for specie. To reach the second object, essences like Angelim Saia (Vatairea sp), Eucalipto Citriodora (Eucalyptus citriodora), Eucalipto Grandis (Eucalyptus grandis), Pinus Elliottü (Pinus elliottii), were employed, with weIl-sampled and climatized specimens, thirty for specie. AlI tests were conducted using 2cm x 2cm x 30cm specimens, according to the indications of Annex B of the Brazilian Standard to the Design of Timber Structures (NBR 7190/1997). Conclusions are interesting contributions to facilitate the required evaluation to improve wood applications, in cases where touglmess parameters are fundamental.
IntroductionA tough piece ofwood is one that sustains large deformation in bending or twisting before rupture. However, strict usage has reserved the term for a particular mechanical property to classify wood under the action of an impact load that causes failure, BODIG & JA YNE (1992). A ductile material that offers the same resistance than a non-ductile material, needs more energy to failure, exhibiting a higher touglmess value, VAN VLACK (1989). Toughness is the work required to break a given specimen onder an impact load, that is, it's the capacity of the material in absorbing energy at plastic zone.Knowledge of physical and mechanical properties of wood makes possible its better use. Since there are difficulties in doing tests to characterize the species, many times wood is applied without knowing its basic properties, resulting in a bad usage and loss. Special importance is regarded on studying behavior of wood, considering need of knowing its performance when it is impacted onder dynamical actions to its appropriate dimensioning of structural elements, furniture and packaging.Touglmess provides precious tools to evaluate the behavior of wood onder dynamical actions. Measurements of toughness are attained from impact bending tests. One of them wiIl be described in details at the following items of this paper.This work, conducted in Wood and Timber Structures Laboratory, Department of Structural Engineering, São Carlos Engineering School, São Paulo University, aims to: a. determin...
A tenacidade da madeira é uma propriedade mecânica de interesse em situações em que o carregamento por impacto deve ser considerado, encontrando aplicação em silos, pontes e fôrmas para estruturas de concreto armado. Apesar das recomendações do Anexo B - NBR 7190:1997, não tem sido usual a determinação da tenacidade na caracterização da madeira. Este trabalho objetivou investigar a influência do teor de umidade (30; 20; 12; 6; 0%) na obtenção da tenacidade da madeira angelim-saia (Vatairea sp), Eucalyptus grandis, Pinus elliottii e Corymbia citriodora, considerando a orientação dos anéis de crescimento em relação à direção da força de impacto. Análises estatísticas dos resultados por análise de variância (ANOVA) e teste de Tukey revelaram ser significativa a influência do teor de umidade na tenacidade apenas para a madeira de angelim-saia. Para as demais espécies, a análise estatística demonstrou resultados estatisticamente equivalentes, ou seja, o teor de umidade não foi influente na propriedade de tenacidade. Neste sentido, foi observado que o teor de umidade pode ser significativo na obtenção da tenacidade conforme a espécie e que maiores teores podem fornecer valores superiores desta propriedade.
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