Edgewise Position Research Articles

A Study of the Properties of UV-Aged and Low Formaldehyde Emissions Particleboards Manufactured with Bio-Based Wood Protein Adhesives

The environmental crisis and the safeguarding of the population's health has led to research into different ways of mitigating harmful gases. Among the emissions that the wood industry has sought to reduce are those of formaldehyde, which is why new green adhesive methods for wood panels have been investigated in recent years. In this research, particleboard with two bio-based wood adhesive (PB-bbwa) formulations. The first PB-bbwa formulation, based on proteins obtained from compounds from the alcoholic beverage industry, and the second PB-bbwa formulation, based on proteins from a mixture of compounds from the alcoholic beverage and food industries, were manufactured and tested to evaluate the physical–mechanical, thermal and formaldehyde emission properties of untreated and UV-treated formulations at a laboratory scale. The results of the physical properties obtained in the PB-bbwa were similar or even better than those of the control PB. Additionally, PB-bbwas improve on the control PB sample’s Janka hardness by least 28%, and a decrease in thermal conductivity in the edgewise position and formaldehyde emissions by 12% and 88%, respectively, in comparison to the control PB. The tests performed evidenced that PB-bbwas showed comparable performance against the control PB made with urea-formaldehyde and satisfied international standard requirements.

Evaluation of tensile and flexural properties of woven glass fiber/epoxy laminated composites oriented in edgewise and flatwise directions

In this study, the tensile and flexural properties of skin-core-skin woven glass fiber/epoxy laminated composites were conducted. Six plies (laminae) for the skins and twenty-four plies for the core were hand-laid up. All plies used had the same dimensions and the same elastic strength where the skins’ plies kept in flatwise direction while the core’s plies oriented in edgewise and flatwise to study the effect of plies alignments and hence loading direction i.e., edgewise (in-plane) and flatwise (out-of-plane) on the materials characteristics. It was observed that the composites oriented in edgewise position had the highest strength of 186 MPa (enhancement 59%) and deformed at higher loads with minor displacements compared to the flatwise strength of 117 MPa. The SEM analysis of the tensile’s fracture surface showed two dominant toughening mechanisms are debonding (fiber pullout) and fiber breakage, while interlaminar/intralaminar delaminated yarns was observed in the flexural fracture surface.

STUDYING THE GRAMMAGE IN LVL PANELS GLUED WITH CASTOR OIL-BASED POLYURETHANE ADHESIVE: A POSSIBLE ALTERNATIVE TO FORMALDEHYDE RELEASING ADHESIVES.

ABSTRACT Efforts have been done in order to decrease the human dependence on petroleum materials. This idea can be applied for wood adhesives and wood products. This study proposes to evaluate laminated veneer lumber (LVL) panels of Hevea brasiliensis produced with castor oil-based polyurethane and resorcinol formaldehyde in different grammages. Six rubber tree (12 years old) with diameters at breast height (DBH) > 25 cm were harvested to generate veneers (500 x 500 x 2 mm; length, width, and thickness, respectively) for the panels production. The veneers were pre classified by a non-destructive impulse excitation method (Sonelastic system). Seven veneers were arranged in the same grain direction to produce each LVL. The following grammages were used for each adhesive type: 240, 280 and 320 g.m-². The volumetric swelling of the panels, glue line strength under dry, wet and post-boiling conditions, and stiffness and strength in static bending tests in flatwise and edgewise positions were evaluated. The glue line was evaluated by optical microscopy. The panels with grammages of 240 g.m-² had the highest volumetric swelling for both adhesives. As the grammage increased from 240 to 280 g.m-², the panel volumetric swelling decreased 32.53% for the resorcinol formaldehyde adhesive and 21.42% for the castor oil-based polyurethane adhesive. The panels glued with the vegetal polyurethane adhesive presented the best results for shear strength in the glue line. No significant statistical differences were found between the compositions for static bending. The results indicate that rubber wood glued with vegetal polyurethane has the potential to be used for production of LVL panels and consequently replace the petroleum based adhesives.

Flexural behavior of composite sandwich beams with different kinds of GFRP ribs in flatwise and edgewise positions

This paper investigated the flexural behavior of composite sandwich beams, composed of glass fiber reinforced polymer (GFRP) skins and a polyurethane (PU) foam core with different kinds of GFRP ribs reinforcement, in flatwise and edgewise positions. The GFRP ribs, consisted of longitudinal, transverse and horizontal ribs, respectively, were embedded inside of the PU foam core. Twenty specimens were tested under four-point bending to verify the influence of the GFRP ribs and beam orientation on the bending stiffness, ultimate load bearing capacity, and failure modes of sandwich beams. It was found that changing the beam orientation from flatwise to edgewise change the beam failure mode from foam core shear failure to skin compressive failure. The sandwich beam's high stiffness and ultimate load bearing capacity can be efficiently utilized by placing them in edgewise position, and the longitudinal ribs played a major role on the bending stiffness and ultimate load bearing capacity compared with the transverse and horizontal ribs in flatwise position. Furthermore, an analytical model accounting for shear and flexural rigidities was proposed to predict the deflection and ultimate load bearing capacity of composite sandwich beams with different kinds of GFRP ribs in flatwise and edgewise positions. The analytical results were agreed well with test results.

Mechanical properties of sandwich composite made of syntactic foam core and GFRP skins

Sandwich composites or sandwich panels have been widely used as potential materials or building structures and are regarded as a lightweight material for marine applications. In particular, the mechanical properties, such as the compressive, tensile and flexural behaviour, of sandwich composites formed from glass fibre sheets used as the skin and glass microballoon/vinyl ester as the syntactic foam core were investigated in this report. This syntactic foam core is sandwiched between unidirectional glass fibre reinforced plastic (GFRP) using vinyl ester resins to build high performance sandwich panels. The results show that the compressive and tensile strengths decrease when the glass microballoon content is increased in syntactic foam core of sandwich panels. Moreover, compressive modulus is also found to be decreased, and there is no trend for tensile modulus. Meanwhile, the flexural stiffness and effective flexural stiffness for edgewise position have a higher bending as 50% and 60%, respectively. Furthermore, the results indicated that the glass microballoon mixed in a vinyl ester should be controlled to obtain a good combination of the tensile, compressive and flexural strength properties.

PROPRIEDADES FÍSICO-MECÂNICAS DE PAINÉIS DE LÂMINAS PARALELAS REFORÇADOS COM PRFV

http://dx.doi.org/10.5902/1980509819676O objetivo desta pesquisa foi avaliar as propriedades físico-mecânicas de painéis de lâminas paralelas (LVL) com camadas de Polímeros Reforçados de Fibra de Vidro (PRFV) impregnadas com dois tipos de matrizes. Primeiramente foi realizada a fabricação dos painéis LVL com nove camadas de lâminas de madeira unidas com resina à base de fenol-formaldeído na gramatura de 190 g/m2 em linha simples. Posteriormente, foi feita a aplicação do reforço de fibra de vidro impregnado com resinas epóxi ou poliéster isoftálica com NPG. Os tratamentos consistiram na aplicação de uma a quatro camadas de fibra de vidro impregnadas com resina epóxi ou isoftálica, totalizando 21 painéis. As propriedades avaliadas foram a massa específica, o teor de umidade, a flexão estática na posição flatwise e egdewise e a resistência ao cisalhamento na linha de cola. Em flexão estática na posição flatwise, uma camada de PRFV, em tratamentos com resina epóxi e isoftálica, foi suficiente para influenciar o módulo de elasticidade (MOE), enquanto para o módulo de ruptura (MOR), duas camadas de PRFV foram necessárias para tratamentos com resina isoftálica e uma camada para tratamentos com resina epóxi. Na posição edgewise, os valores de MOE e do MOR se mantiveram estáveis após a aplicação de duas camadas de PRFV. A resina epóxi apresentou maior resistência ao cisalhamento e maior percentual de falhas na madeira, enquanto a resina isoftálica, apesar de apresentar valores de resistência similares à fenólica, não apresentou boa adesão à madeira, representada pelo baixo percentual de falhas na madeira. Portanto, a aplicação de uma camada de PRFV com resina epóxi na posição de tração seria o suficiente para melhorar as qualidades mecânicas (flexão estática e cisalhamento) dos painéis LVL fabricados com lâminas de madeira de pinus unidas com fenol-formaldeído.

INFLUÊNCIA DE DIFERENTES COMBINAÇÕES DE LÂMINAS DE<i> Eucalyptus saligna</i> E <i>Pinus taeda </i>EM PAINÉIS LVL

http://dx.doi.org/10.5902/1980509817473Investigou-se a influência do posicionamento de lâminas de madeira de Eucalyptus saligna e Pinus taeda nas camadas de painéis Laminated Veneer Lumber (LVL). As composições foram manufaturadas em seis diferentes combinações de cinco lâminas de 3,2 mm de espessura, coladas com adesivo fenol-formaldeído, resultando em tratamentos compostos de madeira de uma mesma espécie e outros com mistura de madeira das duas espécies. A avaliação dos arranjos propostos foi realizada mediante a caracterização de propriedades físicas (teor de umidade e massa específica) e mecânicas (módulo de elasticidade – MOE e módulo de ruptura – MOR), estas verificadas em ensaios de flexão estática flatwise e edgewise. Os resultados obtidos indicaram que, na maior parte das vezes, as diferentes posições das lâminas de maior massa específica (nas camadas externas, intermediárias e de miolo) influenciaram as propriedades mecânicas dos painéis. A influência constatada mostrou-se variada para MOE e MOR, em especial quando comparados valores para os ensaios flatwise e edgewise. Em determinadas posições, nas camadas das composições LVL, a presença de lâminas de eucalipto resultou em aumentos de rigidez e resistência. Contudo, os tratamentos constituídos por lâminas intercaladas de eucalipto e pinus mostraram interessantes performances para uso estrutural, tanto em flatwise quanto em edgewise, por apresentarem valores de MOE e de MOR que permitem distingui-los como de 1ª classe, segundo o documento técnico norte-americano APA/EWS PRL–501 (2001).

Shear behaviour of glued structural fibre composite sandwich beams

The shear behaviour of structural sandwich beams made by gluing together fibre composite sandwich panels in the flatwise and in the edgewise positions was investigated with a view of using this material for construction and building applications. The effect of the number and orientation of sandwich laminations on the shear strength and failure behaviour of glued sandwich beams is examined using an asymmetrical beam shear test. The results showed that the behaviour of the glued sandwich beams in the flatwise position is governed by the shear strength of the core while in the edgewise position by the shear strength of the skin. In the edgewise position, the skin carries almost 60% of the load but only 20% in the flatwise position. With increasing sandwich laminations, the glued sandwich beams in the edgewise position achieved over 200% shear strength than beams in the flatwise position. The presence of vertical fibre composite skins has resulted in a more ductile failure behaviour for beams in the edgewise position. The results of the theoretical and numerical evaluations on the shear strength of the glued sandwich beams using the shear properties of the skin and the core were in good agreement with the experimental results.

Shear Force Capacity of Various Doweled Frame Type Furniture Joints

Tests were carried out to determine the ultimate shear force capacity of numerous of doweled frame type furniture joints under controlled laboratory conditions. Sugar maple (Acer saccharum), soft maple (Acer negund), yellow poplar (Liriodendron tulipifera), sweetgum (Liquidambar styraciflua) and black walnut (Juglans nigra)were utilized in constructing the joint specimens, but all dowels were cut from yellow birch (Betula papyrifera) and sugar maple (Acer saccharum). Two types of specimens were used in the tests, including “in plane” and “out of plane” positions. Specimens were assembled with polyvinyl acetate adhesive. Specimens were tested under static load by applying shear forces. The results showed that the narrower dowel spacing provide greater shear force capacity for a specified rail width. It was deduced that there was a slight relationship between the shear strength of the wood used in the rail and the thickness of the rail and average ultimate shear force capacity of the joint. It was also demonstrated that the joints had essentially equal shear force capacity regardless of whether they were loaded in the flat wise or edgewise position. Furthermore, the average shear force capacity of dowel joints evaluated in this study could be estimated by developed predictive expressions

Obtention and Characterization of Polypropylene, Calcium Carbonate and Poly(ethylene-co-vinyl acetate) Composites

In the increasingly competitive market, the survival of the industries that manufacture components or pieces of polymer is strictly linked to the reduction of production costs. An alternative could be the use of composites of polypropylene, calcium carbonate and poly(ethylene-co-vinyl acetate) for the production of thermoplastics sheets. The thermoplastics sheets obtained by extrusion and co-extrusion processes were characterized through the chemical, physical, thermal, mechanical and morphological characteristics of materials, enabling the performance analysis of the production processes and application to the design of components or parts. The results showed that the addition of 30 wt% CaCO3-EVA increased the thermal stability of polypropylene (PP) around 32°C, decreasing the processing temperature of composites in 15°C, also by decreasing the crystallinity of the polymer from 43% to 30% and the deflection temperature of plastics under flexural load in the edgewise position (DTUL) from 122°C to 107°C. Regarding to the mechanical tests, the yield stress of the composites obtained by extrusion and co-extrusion processes decreased with the addition of CaCO3-EVA. According with the obtained results, we suggest that PP/CaCO3-EVA composites could be used in the production of polymeric parts or components where tensile strengths higher than 25 MPa are not required and for service temperatures between 30°C and 70°C.

Behaviour of glued fibre composite sandwich structure in flexure: Experiment and Fibre Model Analysis

The behaviour of glued composite sandwich beams in flexure was investigated with a view of using this material for structural and civil engineering applications. The building block of this glue-laminated beam is a new generation composite sandwich structure made up of glass fibre reinforced polymer skins and a high strength phenolic core material. A simplified Fibre Model Analysis (FMA) usually used to analyse a concrete beam section is adopted to theoretically describe the flexural behaviour of the innovative sandwich beam structure. The analysis included the flexural behaviour of the glued sandwich beams in the flatwise and the edgewise positions. The FMA accounted for the non-linear behaviour of the phenolic core in compression, the cracking of the core in tension and the linear elastic behaviour of the fibre composite skin. The results of the FMA showed a good agreement with the experimental data showing the efficiency and practical applications of the simplified FMA in analysing and designing sandwich structures with high strength core material.

Propriedades físicas e mecânicas de painéis LVL de <i>Eucalyptus grandis</i>

O presente trabalho teve como objetivo principal avaliar as propriedades físicas e mecânicas de painéis LVL (Laminated veneer lumber) confeccionados com lâminas de Eucalyptus grandis, provenientes de reflorestamentos da região de Sengés, Paraná - Brasil. Foram confeccionados painéis LVL de 23 lâminas, de dimensões comerciais de 2500 mm de comprimento, 1200 mm de largura e espessura nominal de 50 mm (lâminas de 2,4 mm). Em vigas retiradas dos painéis LVL foram analisadas as propriedades de flexão estática (rigidez e resistência), nas condições de menor inércia (flatwise) e de maior inércia (edgewise), compressão paralela, cisalhamento paralelo nos planos L-X e L-Y e densidade, atendendo às prescrições das normas ASTM-D 5456/4761 e ASTM-D 198/143. Os valores médios obtidos para o módulo de elasticidade e resistência à flexão estática foram, respectivamente, 13114 MPa e 88,76 MPa para o ensaio na condição de menor inércia e de, respectivamente, 15871 MPa e 88,63 MPa para o ensaio na condição de maior inércia. A densidade aparente (a 12% de umidade) dos painéis LVL e das lâminas foram, respectivamente, 690 kg/ m3 e 649 kg/m3. Os valores médios obtidos nos ensaios de compressão paralela foram 16856 MPa para o módulo de elasticidade e 58,05 MPa para a resistência. Os valores médios da resistência no ensaio de cisalhamento paralelo no plano L-Y e no plano L-X foram 5,96 MPa e 5,91 MPa, respectivamente. Todos esses valores atingiram parcialmente ou ultrapassaram os limites médios de referência estabelecidos para painéis LVL e para a madeira sólida originária, atestando, sobretudo, a qualidade dos painéis produzidos com essa madeira.

Flexural behaviour of glue-laminated fibre composite sandwich beams

This study involved experimental investigation onto the flexural behaviour of glue-laminated fibre composite sandwich beams with a view of using this material for structural beams. Composite sandwich beams with 1, 2, 3, and 4 composite sandwich panels glued together were subjected to 4-point static bending test in the flatwise and edgewise positions to evaluate their stiffness and strength properties. The results showed that the composite sandwich beams in the edgewise position failed with 25% higher bending strength but have 7% lower bending stiffness than beams in the flatwise position. The results however indicated that the bending stiffness of flatwise specimens converges to that of the edgewise specimens with increasing laminations. More importantly, the specimens in the edgewise position failed with greater ductility due to progressive failure of the fibre composite skins while the specimens in the flatwise position failed in a brittle manner due to debonding between the skin and core. Wrapping the glue-laminated sandwich beams with one layer of tri-axial glass fibres did not prove to be effective. Overall, it has been demonstrated that the glue-laminated sandwich beams exhibited better performance than the individual composite sandwich beams.

Flexural behaviour of structural fibre composite sandwich beams in flatwise and edgewise positions

The flexural behaviour of a new generation composite sandwich beams made up of glass fibre-reinforced polymer skins and modified phenolic core material was investigated. The composite sandwich beams were subjected to 4-point static bending test to determine their strength and failure mechanisms in the flatwise and the edgewise positions. The results of the experimental investigation showed that the composite sandwich beams tested in the edgewise position failed at a higher load with less deflection compared to specimens tested in the flatwise position. Under flexural loading, the composite sandwich beams in the edgewise position failed due to progressive failure of the skin while failure in the flatwise position is in a brittle manner due to either shear failure of the core or compressive failure of the skin followed by debonding between the skin and the core. The results of the analytical predictions and numerical simulations are in good agreement with the experimental results.

Sedimentation of solid discs in viscous medium

Free sedimentation velocities of thin discs have been measured in castor oil and liquid paraffin at constant temperature. ‘Wall’ and ‘end’ corrections have been applied to the measured velocities and the corrected values have been compared with those calculated fromOverbeck andGans' equations. Sedimentation velocities have been measured in both edgewise and broadsideon positions. Good agreements have been obtained with the theory in both types of sedimentation. The broadsideon position has been found to be the preferred orientation and all particles deviating even slightly from the edgewise position take the preferred orientation quickly. Results of other investigators have been discussed in the light of the present findings.