Abstract NBR 7190 (ABNT, 1997) defines the simplified characterization, where there is the use of mathematical relationships between the properties of strength and stiffness. Due to the great influence of porosity and apparent density on wood properties and the search for increasingly accurate mathematical models, this work aimed to generate regression models for the estimation of static bending properties (strength " f M " and modulus " E M "), hardness parallel to the grain " f H,0 " and normal to the grain " f H,90 " and toughness "W" of Brazilian tropical woods from the porosity values, obtained through the analysis mercury instruction porosimetry, apparent density and based on both properties in multivariate regression models. All regression models presented coefficients of determination "R 2 " greater than 50%, where f M , f H,90 and W were best estimated by density apparent, E M and f H,0 were better estimated considering apparent density and porosity.

Resumo ANBR 7190 (ABNT, 1997) define a caracterização simplificada, onde há o uso de relações matemáticas entre as propriedades de resistência e rigidez. Devido à grande influência da porosidade e da densidade aparente nas propriedades das madeiras e à busca por modelos matemáticos cada vez mais precisos, este trabalho teve como objetivo’ gerar modelos de regressão para a estimativa das propriedades de flexão estática (resistência “f M ” e módulo “E M ”), resistência à dureza paralela “f H,0 ” e normal às fibras “f H,90 ”, e resistência à tenacidade “W” de madeiras tropicais brasileiras a partir dos valores de porosidade, obtidos por meio da análise de porosimetria por intrusão de mercúrio, da densidade aparente e com base em ambas as propriedades em modelos de regressão multivariáveis. Todos os modelos de regressão apresentaram coeficientes de determinação “R2” superiores a 50%. A f M , a f H,90 e a W foram melhor estimadas pela densidade aparente, enquanto o E M e a f H,0 foram melhor estimados considerando a densidade aparente e a porosidade.

ABSTRACT To simplify the characterization of wood species, the Brazilian standard document ABNT NBR 7190-1 (2022) establishes the determination of mechanical properties employing the characteristic strength in the compression parallel to grain (fc0,k). This mechanical property is estimated using the linear relation given by the following expression fv0,k = 0.12·fc0,k Brazilian and European standard documents support the estimation of fv0,k using relations among properties. However, the European guidelines in the EN 384 (2019) have used the conventional characteristic strength in the static bending test (fM,k). Thus, this study aimed to investigate the efficiency of the ratio fv0,k = 0.12·fc0,k for adopting 30 hardwoods. The variance analysis results demonstrate the divergence among the experimental outcomes and those values estimated using the relation cited. Therefore, regression models at two parameters were considered to obtain more accurate estimates of fv0,k by adopting fc0,k, and fM,k as independent variables. Regarding the results, the geometric (R² = 80.80%) and linear (R² = 74.19%) models were the most accurate for the estimates of fv0,k in terms of fc0,k, and fM,k, respectively. This fact evinces the good accuracy of the models under consideration, which may provide a more rigorous structural design compared to the correlation currently prescribed by the ABNT NBR 7190-1 (2022).

RESUMO Para simplificar a caracterização de espécies de madeira, o documento normativo brasileiro ABNT NBR 7190-1 (2022) estabelece a determinação de propriedades mecânicas por meio da resistência característica na compressão paralela às fibras (fc0,k). Essa propriedade mecânica é estimada utilizando-se da relação linear dada pela expressão a seguir fv0,k = 0.12·fc0,k. Ambos os documentos normativos europeu e brasileiro prescrevem a estimativa da fv0,k empregando-se relações entre propriedades, embora as diretrizes da europeia contidas na EN 384 (2019) utilize a resistência característica convencional obtida no teste de flexão estática (fM,k). Assim, esse estudo teve o objetivo de investigar a eficiência da relação fv0,k = 0.12·fc0,k para 30 espécies folhosas. Os resultados da análise de variância demonstram a divergência entre os resultados experimentais e aqueles estimados utilizando-se da relação citada. Portanto, modelos de regressão em função de dois parâmetros foram considerados para se obter estimativas mais precisas da fv0,k através da adoção da fc0,k e fM,k como variáveis independentes. Com relação aos resultados, os modelos geométrico (R² = 80.80%) e linear (R² = 74.19%) foram os mais precisos para a estimativa da fv0,k em termos da fc0,k e fM,k, respectivamente. Este fato evidencia a boa precisão dos modelos em questão, o que pode proporcionar um dimensionamento estrutural mais rigoroso quando comparado à correlação atualmente prescrita pela ABNT NBR 7190-1 (2022).

ABSTRACT Wood has several properties that make it attractive when compared to other materials, however, for its use, it is necessary to know the values of resistance and stiffness. In this sense, the use of non-destructive techniques adds to the process. Among the non-destructive techniques of mechanical evaluation, we highlight those that use the natural frequencies of vibration whose results can be repeated and compared over time. This research aimed to relate the physical and mechanical properties of cajueiro wood [Anacardium sp], with the apparent density and with the natural frequency of the transversal vibration test, through regression models. Twenty-four transverse vibration tests and 204 experimental determinations were performed. Linear regression models were then generated as a function of apparent density and transverse vibration frequency, as well as quadratic multivariable regression models, to estimate wood properties. From the linear regression models, weak correlations were noted between density and natural frequency with the physico-mechanical properties evaluated, resulting in low precision estimates. Regarding the multivariable regression models, quadratic adjusted coefficients of determination (R²aj) higher than 80% were verified for 03 models of the 16 evaluated.

RESUMO A madeira possui diversas propriedades que a torna atraente frente a outros materiais, entretanto, para sua utilização, com segurança, é necessário o conhecimento dos valores de resistência e elasticidade. Nesse sentido, a utilização de técnicas não destrutivas vem a agregar no processo de avaliação. Entre as técnicas não destrutivas de avaliação mecânica, destacam-se aquelas que utilizam as frequências naturais de vibração cujos resultados podem ser repetidos e comparados ao longo do tempo. Esta pesquisa objetivou relacionar as propriedades físicas e mecânicas da madeira de cajueiro [Anacardium sp], com a densidade aparente e com a frequência natural do ensaio de vibração transversal, por meio de modelos de regressão. Foram realizados 24 ensaios de vibração transversal e mais 204 determinações experimentais. Na sequência, foram gerados modelos de regressão lineares em função da densidade aparente e da frequência de vibração transversal, bem como modelos de regressão multivariáveis quadráticos, de forma a estimar as propriedades das madeiras. Dos modelos de regressão lineares, foram notadas fracas correlações entre a densidade e a frequência natural com as propriedades físico-mecânicas avaliadas, resultando em estimativas de baixa precisão. Em relação aos modelos de regressão multivariáveis, quadráticos foram verificados coeficientes de determinação ajustado (R²aj) superiores a 80 % para 03 modelos dos 16 avaliados.

Abstract The objective of this research is to evaluate the possibility of use of tropical hardwood species (Amburana cearensis and Cedrella fissilis) for grilling plank production. Physical, chemical and organoleptic properties were evaluated and compared with properties of a well-used wood specie for grilling plank across Europe and USA, Western Red Cedar (Thuja plicata). For chemical analysis, three techniques were used: hydro distillation, soxhlet and head space. Normality test and analysis of variance (ANOVA) were used for the comparison between Thuja plicata and tropical hardwoods. The results of organoleptic, chemical and statistical analysis demonstrated the possibility of use of Amburana cearensis and Cedrella fissilis on grilling plank production, with no volatile compound present in these species being toxic, low apparent density and Nerolidol presence, chemical compound used as flavoring agent, enabling their use as grilling planks.

Abstract This work investigates the effect of eco-friendly chemical treatments on the mechanical and physical properties of composite laminates based on sisal fibres. A 2231 full-factorial design is conducted to test the influence of chemical solution types, fibre treatment time, and polymer matrix type on the mechanical and morphological characterisation of the composites. Chemical treatments remove impurities from fibre surfaces, and enhance fibre-matrix adhesion. The treatments, especially with sodium carbonate (Na2CO3), also progressively reduce the hemicellulose fibre content. Polyester composites made with sisal fibres treated with Na2CO3 for 96h achieve enhanced strength and stiffness under tensile, compressive and impact loads. The results evidence the feasibility and efficiency of the proposed eco-friendly treatments for natural fibres and the application of renewable fibre laminates in secondary structural applications.

RESUMO Neste trabalho avaliou-se numericamente a influência do módulo de elasticidade paralelo às fibras da madeira na estabilidade de arcos treliçados, considerando uma análise não linear geométrica baseada no Método dos Elementos Finitos (MEF). Essa abordagem foi realizada conforme uma formulação posicional do MEF, atribuindo-se os nós da estrutura como variáveis principais do sistema de equações não lineares, cuja resolução foi alcançada pelo método de Newton-Raphson. Ao todo, sete modelos de arco foram avaliados adotando-se madeiras coníferas e folhosas, com propriedades definidas segundo as classes de resistência da norma brasileira ABNT NBR 7190. Subrotinas foram desenvolvidas em linguagem MATLAB para resolução do sistema de equações não lineares e processamento da análise, incluindo a representação gráfica dos resultados e configurações do arco treliçado. Valores de esforços internos e deslocamentos foram determinados, assim como as forças de instabilidade dos arcos treliçados. Verificou-se que a força de instabilidade do arco constituído pela madeira folhosa mais rígida (D60) foi aproximadamente igual a 700% da força de instabilidade referente à classe conífera C20, e equivalente a 257,8% da força associada à classe folhosa D20. Concluiu-se que o módulo de elasticidade apresentou influência significativa no comportamento não linear geométrico do arco treliçado de madeira. Além disso, a análise não linear geométrica possibilitou o cálculo de parâmetros mais precisos e a verificação da estabilidade do sistema estrutural.

ABSTRACT In this work, it was numerically evaluated the influence of the modulus of elasticity parallel to the wood grain on the stability of trussed arches considering a nonlinear geometric analysis based on the Finite Element Method (FEM). This approach was carried out according to a positional formulation of the FEM, considering the structural nodes as main variables of the nonlinear equations system, whose resolution was obtained using the Newton-Raphson method. Altogether, seven arch models were evaluated, consisting of coniferous and hardwoods, with properties defined according to the strength classes of the Brazilian standard ABNT NBR 7190. The subroutines were written in MATLAB to solve the system of nonlinear equations and perform the analysis, including the graphical representation of the results and configurations of the trussed arch. Internal loads and displacements were obtained, in addition to the instability loads of the trussed arches. It was found that the instability load of the arch made with the stiffest hardwood (D60) was approximately equal to 700% of the instability load of the C20 coniferous class and equivalent to 257.8% of the D20 hardwood class-related load. It was verified that the modulus of elasticity significantly influences the nonlinear geometric behavior of the timber trussed arch. Furthermore, the nonlinear geometric analysis allowed calculating more accurate parameters and the verification of the stability of the structural system.

Abstract The present study aimed to characterize medium density particleboard manufactured with CCB treated particles of Pinus sp. wood specie and alternative mixed vegetal oil-base bicomponent polyurethane resin. For this, three different resin concentrations (10 %, 12 % and 15 %) were used in combination with the presence or absence of the CCB preservative, resulting in six distinct treatments. The particleboards were produced according the Brazilian Standard - NBR and evaluated according European standards - EN. The results met the requirements of NBR and EN. The technical feasibility of making panels with those materials used were proved and the quality of the product according to its performance were verified, indicating the possibility to use alternative bicomponent polyurethane resin from mix vegetal oil. Statistical analysis demonstrated that adhesive and preservative factors and the interaction between them were significant on physical and mechanical properties.

Abstract Natural fibres have many advantages over synthetic ones, making them attractive for reinforcing polymer materials. This work evaluates the use of an Amazonian plant, namely Curauá (Ananas erectifolius), as a reinforcement phase of biocomposites fabricated by cold pressing. Curauá fibres have been shown to be a promising fibre for composite materials, especially due to their higher elastic modulus than other plant species. An L9 Taguchi design is used to investigate the effect of fibre fraction, NaOH concentration and immersion time on the tensile properties of biocomposites. Statistical models are able of predicting and revealing the optimal composition of the biocomposites. The tensile strength of Curauá biocomposites is significantly affected by the fibre fraction, followed by the factors of immersion time and NaOH concentration. High tensile strength is obtained by adding 25 wt.% of Curauá fibres treated under different conditions. There is an interaction between NaOH concentration and the immersion time; a higher concentration requires less time or vice versa to achieve ideal roughness, promoting strong fibre/matrix adhesion.

RESUMO A madeira é um importante material de construção usado em estruturas de cobertura de telhados, pontes, viadutos e passarelas. Para melhorar o seu uso, bem como reabilitar partes estruturais deterioradas pela ação do tempo, o reforço de vigas e pilares com material compósito é utilizado. Considerando a ação do tempo na estrutura, é importante conhecer a influência e comportamento da madeira e do material compósito quando submetido ao intemperismo. Essa pesquisa objetifica avaliar a influência do reforço com CFRP (Carbon Fiber Reinforced Polymer) na madeira tratada com o preservativo CCB submetida à ação do intemperismo acelerado na resistência a tração paralela às fibras. Os resultados mostraram uma redução de 30% na resistência devido ao intemperismo acelerado, e um aumento da resistência à tração de 25%, mostrando assim, a influência positiva do reforço, mesmo em condições de intemperismo artificial.

ABSTRACT Wood is an important building material used in roof structures, bridges, viaducts, and pedestrian bridges. In order to improve its use, as well as rehabilitate structural parts deteriorated by weathering, reinforcement of beams and columns with composite material is performed. Given the climate action on structures, it is important to know the influence and behavior of wood and composite material when subjected to weathering. This study aimed to evaluate the influence of the reinforcement of CCB-treated wood with carbon fiber reinforced polymer (CFRP) and subjected to artificial weathering on its tensile strength parallel to the fibers. The results showed a 30% reduction in strength due to weathering and a 25% increase in tensile strength, showing the positive influence of reinforcement even under artificial weathering conditions

RESUMO Por ser um material anisotrópico e heterogêneo, o uso racional da madeira em estruturas requer o conhecimento de uma série de propriedades físicas e mecânicas. Parte das propriedades é obtida com o uso de equipamentos de grande porte, geralmente encontrados em poucos centros de pesquisas. A vibração transversal consiste em um método de ensaio não destrutivo utilizado na determinação da rigidez da madeira, em função agilidade proporcionada na realização dos ensaios. Essa pesquisa objetivou, com base na obtenção de dezessete propriedades entre físicas e mecânicas da madeira de Mandioqueira [Ruizterania albiflora (Warm.) Marc. -Berti, Vochysiaceae], espécie pouco conhecida na literatura nacional e internacional, avaliar a indicação de uso e relacionar suas propriedades físicas (estabilidade dimensional) e mecânicas (resistência e rigidez) com a densidade aparente e com a frequência natural do ensaio de vibração transversal por meio de modelos de regressão. Os resultados indicam o uso da madeira de Mandioqueira em estruturas, por apresentar propriedades equivalentes ou superiores às propriedades de outras comumente utilizadas na construção civil. Dos modelos de regressão, foram notadas fracas correlações entre a densidade e a frequência natural com as propriedades físico-mecânicas avaliadas, resultando em estimativas de baixa precisão. Entretanto, resultados mais abrangentes requerem maior número de espécies, e consistirão em objetivos de pesquisas futuras.

ABSTRACT As it is an anisotropic and heterogeneous material, the rational use of wood in structures requires knowledge of a series of physical and mechanical properties. Part of the properties is obtained with the use of large equipment, generally found in a few research centers. Transverse vibration consists of a non-destructive test method used to determine the stiffness of the wood, due to the agility provided in carrying out the tests. This research aimed, based on obtaining seventeen physical and mechanical properties of Mandioqueira wood [Ruizterania albiflora (Warm.) Marc.- Berti, Vochysiaceae], a little known species in national and international literature, evaluate the indication of use and relate its properties physical (dimensional stability) and mechanical (strength and stiffness) to the apparent density and to the natural frequency of the transversal vibration test by means of regression models. The results indicate the use of Mandioqueira wood in structures, as it has properties equivalent or superior to the properties of others commonly used in civil construction. From the regression models, weak correlations were observed between density and natural frequency with the evaluated physical-mechanical properties, resulting in low precision estimates. However, more comprehensive results require a greater number of species, and will consist in the objectives for future research.

Abstract: This research intends to evaluate the relation, aided by the Brazilian Standard and statistical analysis (Kruskal-Wallis ANOVA and bootstrap technique), between physical and mechanical properties of Cambará-Rosa wood harvested from three different regions: Vera, Mucajaí and South Rondonia. In addition, the possibility to estimate (regression models) physical and mechanical properties in function of apparent density was analyzed. Different climate and soil conditions which tree thrives may influence its growth and, consequently, its properties values. The results of ANOVA indicated an elevated equivalence index for all three regions. The bootstrap technique led to similar results for Vera and Mucajai regions, and for South Rondonia region, equivalence index equals to 89 %. The ANOVA results to estimate physical and mechanical properties in function of apparent density indicated that it is not possible to perform such estimates for Cambará-Rosa wood species.

Abstract This work investigates the mechanical behaviour of a sustainable sandwich panel, consisting of bamboo rings core, treated aluminium skins and epoxy adhesive. A Design of Experiment (DoE) is used to identify the effects of bamboo diameters (30 and 45 mm) and aluminium skin treatments (alkaline degreasing and application of primer) on the mechanical and physical properties of sandwich panels. The aluminium skins treated with the wash primer significantly increase adhesion to the polymer, resulting in greater maximum load, flexural strength, maximum skin stress and maximum core shear stress; while the skins treated with NaOH resulted in a greater flexural and core shear modulus. Relatively more rigid and resistant structures are obtained with Ø30 mm rings, due to the increased surface contact area and the number of constraints on the core. The samples fail due to the skin fracture, implying an efficient face-core bond that is attributed to the proper absorption of the polymer by bamboo and the treatment of the aluminium surface. The proposed panels present good mechanical performance, proving to be a feasible and promising alternative for secondary structural applications.

Resumo Neste trabalho foi investigada a influência da inclusão de frações mássicas de cimento Portland (CP-V ARI) [0%, 10%, 20% e 30%] a título de simular parcelas de resíduo de construção civil que tenha frações cimentícias não hidratadas na produção de painéis de partículas compostos de madeira de Pinus sp. e resina poliuretana à base de mamona, buscando avaliar o potencial de painéis produzidos com adição de materiais granulares como resíduos de construção civil. A caracterização física e mecânica de painéis MDP com adição de cimento foi feita com o auxílio da norma brasileira NBR 14810 e da análise de variância (ANOVA), sendo analisadas as propriedades físicas e mecânicas. Foram fabricados 4 painéis de 400 mm x 400 mm x 10 mm com partículas de Pinus sp. e resina poliuretana à base de óleo de mamona com teor de adesivo igual a 10% em relação à massa seca de partículas, para cada tratamento, totalizando 16 painéis. Para cada painel foram retirados 3 corpos de prova (CP) para avaliação das propriedades físicas e mecânicas. A adição de frações mássicas de cimento acima de 10% impactou negativamente as propriedades mecânicas dos painéis, por ter diminuído os valores de MOE e MOR. As propriedades de densidade, absorção e inchamento se mantiveram dentro dos requisitos da norma.

Abstract This research study investigates the influence of the inclusion of Portland cement mass fractions (CP-V ARI) [0%, 10%, 20% and 30%] on the production of composite wood panels made with Pinus sp. and castor oil-based polyurethane resin, with the aim of evaluating the potential of panels produced with the addition of granular materials as construction waste. The characterisation was performed with the aid of the Brazilian standard NBR 14810 and an analysis of variance (ANOVA), analysing the physical and mechanical properties. Four 400 mm x 400 mm x 10 mm panels were manufactured for each treatment, totalling 16 panels. For each panel, 3 test specimens (CP) were taken for an evaluation of their physical and mechanical properties. The addition of mass fractions of cement larger than 10% are detrimental to the mechanical properties of the panels, reducing the MOE and MOR values. The density, absorption and swelling properties remained within the requirements of the standard.

Abstract: Wood strength values are calculated based on the characteristic value, which corresponds to the 5 % percentile of a given probability distribution model. For a few number of samples (12 samples), the Brazilian standard establishes an estimator of the characteristic compressive strength parallel to grain of the wood, which may provide a different result when compared with the characteristic value coming from a suitable probability distribution model. Considering the strength results in the parallel compression to the grain of 45 wood species of the hardwood group, Normal, LogNormal, Weibull and Exponential probability distribution models were used for each specie with the purpose of determining the one with the highest adhesion. Calculated the characteristic values by the best probability model distribution, an analysis of variance (ANOVA) was performed in the estimation of the characteristic value of compressive strength, making it possible to identify the most significant terms of the models as well as the quality of the adjustment obtained on such models. The proposed regression model (R2 adj= 96,56 %) proved to be equivalent to the empirical model of the Brazilian standard. The model proposed here only depends on the mean and the lowest value obtained from the compressive strength in the parallel direction to the grain.

Resumo Dentre os fatores envolvidos na fabricação dos painéis destaca-se o tipo adesivo, em que o uso de novos pode resultar em boas propriedades aos materiais fabricados. Nesse contexto, esta pesquisa objetivou avaliar propriedades físicas e mecânicas de painéis de partículas fabricados com madeiras de Pinus sp. e de Eucalyptus grandis e unidas com resina poliuretana monocomponente derivada do óleo de mamona, cujo desenvolvimento desse adesivo vem sendo sistematicamente aperfeiçoado por diversos fabricantes. Foram produzidos dez painéis para cada espécie de madeira, ambos fabricados sobre as mesmas condições experimentais: 640 g de partículas (teor de umidade próximo de 10%), teor de adesivo de 15% sobre a massa de partículas, 10 min de tempo de prensagem a 100 ºC sob pressão de 4,0 MPa, consistindo nos mesmos parâmetros utilizados na fabricação de painéis de partículas de outras pesquisas, mas com o uso da resina bicomponente à base de mamona. Os painéis foram caracterizados segundo premissas e métodos de cálculo da norma brasileira NBR 14810-2 (2013), sendo utilizadas também normas internacionais para a verificação do requisitos. Com exceção da resistência ao arrancamento de parafuso, as demais propriedades obtidas superaram os requisitos dos documentos normativos utilizados.

Abstract One of the main factors involved in the manufacture of panels is the adhesive type, in which the use of new adhesives can offer positive properties to the manufactured materials. This research study aimed to evaluate the physical and mechanical properties of particleboard made from Pinus sp. and Eucalyptus grandis wood adhered with monocomponent castor oil-based polyurethane resin, whose development has been systematically improved by several manufacturers. Ten particleboards were produced for each wood species evaluated, both manufactured using the same parameters and under the same experimental conditions: 640g of particles (approximately 10% moisture content), 15% adhesive content based on the particle mass, 10 min press time at 100ºC under a pressure of 4.0 MPa, consisting of the same parameters used in the manufacture of particleboards adopted in other research studies, but produced with bicomponent castor oil-based polyurethane resin. The panels were characterized according to the assumptions and methods of calculation specified in the Brazilian standard NBR 14810-2 (2013), using also the international standards for the verification of the requirements. With the exception of the screw pulling strength, the other properties obtained exceeded the requirements of the normative standards used.