Influence of Physical and Chemical Components on the Physical-Mechanical Properties of Ten Brazilian Wood Species

In Brazil, standard ABNT NBR 7190 (1997) prescribes the determination of strength (fM) and modulus of elasticity (EM) in static bending from specimens measuring 5 cm × 5 cm × 115 cm. Thus, the relationship between the test span (L) and the specimen height (h) greater than or equal to 21 (L/h ≥ 21) is respected, ensuring that the effect of shear in the calculation of displacements is negligible (Euler Bernoulli Theory). Considering the expressive number of tree species cataloged in the Brazilian Amazon Forest, any procedure that aims to facilitate the realization of experimental tests is highly desirable because it provides the knowledge of unusual species. These wood species may potentially replace woods that have been traditionally used and historically exploited. Using five hardwood species, this research aimed to verify, while maintaining constant L/h ≥ 21 ratios, the influence of specimens dimensions in the determination of fM and EM. For all species studied, the statistical analysis found equivalence in the values of fM and EM determined as a function of the sample sizes. Therefore, respecting the ratio L/h ≥ 21, the size of the specimens does not influence the determination of strength and stiffness in static bending.

Section: Resultssupporting

confidence: 91%

Influence of specimen dimensions in the determination of strength and modulus of elasticity in static bending of hardwoods

Almeida

Rodrigues

Mascarenhas

et al. 2022

“…For class C30, which corresponds to 10.13% of the total evaluated species, the value of R² (83.76%) is indicative of a strong relationship between anatomy, apparent density, and strength to compression parallel to the fibers (Duarte et al 2020). It should be noted that the same precision degree (R² = 19.97%) was not obtained for class C20, even with a higher number of species (13.92% of the total) when compared to C30.…”

Section: Regression Modelsmentioning

confidence: 99%

Models to estimate longitudinal compressive strength of Brazilian hardwood based on apparent density

Lahr

Arroyo

Rodrigues

et al. 2021

Self Cite

As wood is an orthotropic and natural material, there are several properties required for its use in civil construction. The apparent density has been used to estimate physical and mechanical properties of wood, as it is easy to determine experimentally, unlike other determinations, which involve the use of equipment available only in large research centers. Using the Brazilian standard ABNT NBR 7190 and linear and non-linear regression models, this research aimed to evaluate their accuracy in estimating the compressive strength parallel to the fibers (fc0) as well as their characteristic value (fc0,k). This study considered 72 tropical wood species from native forests that were divided into the 4 strength classes of this standard. For the set formed by all species, the linear polynomial model was the best fit, resulting in a determination coefficient of just over 70%.

“…The natural durability of the wood is conferred by its secondary components that, in most cases, are present in small proportions, but can, in some species, reach high values, such as those found by Duarte et al (2020), when determining the levels of D. odorata extractives and obtaining values of approximately 12.7%. Stangerlin et al (2013) obtained percentage values of extractives that ranged between 2% and 9% in the wood of native species, such as marupá, jequitibá, and cumaru.…”

Section: Chemical Analysismentioning

confidence: 99%

Crystallinity and chemical structure of Amazon wood species in a log yard after natural degradation

Sampaio,

Andrade,

Moutinho

et al. 2023

The objective of this work was to evaluate whether the chemical composition of wood and its crystallinity can help in the analysis of degradation by fungi and insects in logs of Amazonian wood species stored in a stockyard. For this study, wood from five commercial species that had been stored in an open yard for six months was used. The scale of degradation by fungi and insects, the moisture content of the logs, the total extractive content, lignin, holocellulose and the crystallinity were evaluated. It was concluded that the position of the logs in the stacks, associated with the storage time, influenced the evaluated characteristics. It was also observed that X-ray diffraction has potential for analysis of the degradation by fungi and insects in logs of Amazonian species stored in the stockyard.