Strength Parallel Research Articles

Effect of spacing on some mechanical properties of narrow leaved ash (Fraxinus angustifolia) wood

In this study, conducted to test the effect of spacing on wood quality; the effect of four different spacing types, applied in Adapazari Suleymaniye plantation (Region 1; 3x2 m; Region 2; 3x2,5 m; Region 3; 3,75x3,75 m; Region 4; 4x4 m), on some mechanical properties of narrow leaved ash (Fraxinus angustifolia) have been studied. In the present study, some mechanical properties such as the compression strength parallel to grain, tensile stress perpendicular to grain, bending strength, impact bending strength and modulus of elasticity were determined. As a result, the ash wood, grown in region 4 with a wide range of planting, has high mechanical properties. However, when analyzed in terms of wood quality characteristics, it has been found that spacing in region 1 (2x3 m) is more suitable for applications of ash plantations.

Mechanical properties of chemically modified portuguese pinewood

To turn wood into a construction material with enhanced properties, many methods of chemical modification have been developed in the last few decades. In this work, mechanical properties of pine wood were chemically modified, compared and evaluated. Maritime pine wood (Pinus pinaster) was modified with four chemical processes: 1,3-dimethylol-4,5-dihydroxyethyleneurea, N-methylol melamine formaldehyde, tetra- alkoxysilane and wax. The following mechanical properties were assessed experimentally: Modulus of elasticity measured statically, stiffness stabilization efficiency in different climates (30 and 87% of relative humidity), modulus of rupture, work maximum load, impact bending strength, compression, tensile and shear strength at indoor conditions (65% of relative humidity). In both types of active principle of modification, cell wall or lumen fill, no significant changes on the bending stiffness (modulus of elasticity) were found. In the remaining properties analysed significant changes in the modified wood-material took place compared to unmodified wood control: - Cell wall modification was the most effective method to achieve high stiffness stabilization efficiency (up to 60%) and also increased compression strength (up to 230%). However, modulus of rupture, tensile, shear and the impact bending strength were reduced by both resins, but in a varying extent, where the N-methylol melamine formaldehyde endured less reduction than 1,3-dimethylol-4,5-dihydroxyethyleneurea resin. In the latter, reduction up to 60% can take place. - In the lumen fill modification: tetra-alkoxysilane has no effect in the mechanical properties. Although, a slight increase in shear strength parallel to the grain was found. Wax specimens have shown a slight increase in bending strength, compression, tensile and shear strength as well as in the absorption energy capacity.

Mechanical properties and chemical composition of beech wood exposed for 30 and 120 days to white-rot fungi

Abstract The effects of exposing specimens of Oriental beech [Fagus sylvatica subsp. orientalis (Lipsky) Greuter and Burdet] to the white-rot fungi Pleurotus ostreatus (Jacq.: Fr.) Kummer and Trametes versicolor (L.: Fr.) Pilát strain 325 have been studied concerning the mechanical properties and chemical composition in terms of carbohydrates, cellulose, and lignin. Biological decay tests were carried out in accordance with the EN 113 standard specifications for 30 and 120 days. P. ostreatus had nearly the same deteriorating effects on the mechanical properties and chemical composition as that caused by T. versicolor. High and significant correlations were found between some mechanical properties with chemical components; for instance, the correlation coefficient (R2) between impact bending and carbohydrate content was about 0.96. The changes of components influence the various mechanical properties to a different degree. Incipient fungal decay caused severe changes for impact bending and carbohydrate loss. Several other properties declined at 120-day exposure time, such as the hardness, compression strength parallel to grain, and cellulose and lignin losses.

Investigating the anisotropic mechanical properties of plasma sprayed yttria-stabilised zirconia coatings

The adhesion and cohesion bond strengths of plasma sprayed yttria-stabilised zirconia (YSZ) coatings were measured by performing the tensile adhesion test (TAT) and the tubular coating tensile test (TCTT). The TAT allowed assessment of adhesive/cohesive bond strength of a coating microstructure perpendicular to the substrate. In contrast, the TCTT quantifies the strength of a thermal spray coating parallel to the substrate without the use of any adhesive. The failure strength of the coatings from the respective tests can be approximated to a Weibull distribution and indicated the anisotropic behaviour of plasma sprayed coatings. The average coating strength parallel to the substrate is approximately 1.5 times greater than the bond strength perpendicular to substrate. The anisotropic behaviour of the plasma sprayed YSZ coatings were also probed using Knoop hardness measurements that were orientated at a well-defined geometry with respect to the lamellar microstructure. In addition, uniaxial compression tests evaluated the Poisson's ratio of these anisotropic YSZ coatings when loaded with respect to the different microstructural orientations.

Vybrané vlastnosti dřeva smrku pichlavého (Picea pungens Engelm.) z nelesních půd

The aim of this work was to carry out a tree-ring analysis, to determine density, shrinkage and compressive strength parallel to the grain of Blue spruce (Picea pungens Engelm.) wood. Results of this work were specific due to the non-forest origin of the sample material that was from two solitaire trees. Tree ring analysis (determination of tree ring width and portion of latewood) was carried out on the transverse section of a stem that was taken at height of 0.3 m from the tree base. Wood properties were tested according to Czech technical standards.Trees showed wide tree rings (5.65 mm) with a small portion of latewood (12.55 %). Oven dry wood density was 371.66 kg . m−3, overall volumetric shrinkage was 9.12 % and compressive strength parallel to the grain was 42.10 MPa. Due to the low age of trees results are valid for juvenile wood.Wood properties were examined along the stem radius. Tree ring width was increasing to the age of 12th year subsequently it was constant. Tree ring width was constant along the entire stem radius. Wood density, overall volumetric shrinkage and compressive strength parallel to the grain were increasing in the direction from pith to bark.

Impact of Dmdheu Resin Treatment on the Mechanical Properties of Poplar

To increase the utilization and the value of poplar, various concentrations of dimethylol dihydroxy ethylene urea (DMDHEU) were used to impregnate poplar, an important tree specie from the north of China. The resin was fixed on the timber under certain conditions, after which the weight percent gain (WPG), flexural modulus (MOR), modulus of elasticity (MOE), impact strength, hardness and compressive strength of the poplar impregnated were tested and evaluated. The results showed that WPG of poplar is positively associated with the concentrations of DMDHEU after the resin treatment; when the WPG of poplar was 62.1% and the concentration of resin was 30%, the concentration of resin shows positive correlation with MOE, the hardness of each section, the compression strength perpendicular to grain, and the compressive strength parallel to the grain, but demonstrates negative correlation with MOR and impact strength.

Influence of Moisture Content in some Mechanical Properties of Two Brazilian Tropical Wood Species

This study aimed, with the aid of analysis of variance (ANOVA), to investigate and quantify the influence of moisture ranging between 12% and over 30% (fiber saturation) on the mechanical properties: strength and modulus of elasticity in compression and in tension parallel to grain; modulus of rupture and modulus of elasticity in static bending; shear strength parallel to grain considering wood species Ipê (Tabebuia sp) and Angelim Araroba (Vataireopsis araroba). Tests were performed according to the assumptions and calculating methods Brazilian standard ABNT NBR 7190, Anexx B, totalizing 400 tests. Results of ANOVA revealed a significant reduction (16% on average) for mechanical properties wood due to the increase in moisture content from 12% to over 30% (fiber saturation). The same behavior also occurred when assembly containing the two species was considered.

Degradation assessment of waterlogged wood at Haimenkou site

Haimenkou site is the largest railing-enclosed wooden architecture settlement site on the waterfront in current China. This research conducts degradation assessment of waterlogged wood at Haimenkou site with various methods, including maximum moisture content analysis, basic density analysis, shrinkage measurement, swelling analysis, chemical composition analysis, measurement of compression strength parallel to grain, SEM microstructure analysis and measurement of crystallinity, providing scientific guidance for the subsequent formulation of proper methods of reinforcement.

Influence of characteristic inhomogeneity of bamboo culm on mechanical properties of bamboo plywood: effect of culm height

The aim of this study was to evaluate the influence of Neosinocalamus affinis bamboo culm height on selected properties of original bamboo and the mechanical properties of bamboo plywood (BP). The results indicated that vascular bundle density, fiber proportion, specific gravity and compression strength parallel to grain (CSPG) increased from culm bottom to top. Bamboo culm height could significantly affect the mechanical properties of the BP. The shear strength (SS) of the BP decreased with increasing culm height, while the compressive strength (CS) increased. The maximum modulus of rupture (MOR) and tensile strength (TS) was observed at middle portion of culm. Significant correlation was found between vascular bundle density, specific gravity, culm wall thickness of original bamboo and the CS, SS of the BP.

Characterization of Ailanthus altissima Veneer Modified by Urea-formaldehyde Pre-polymer with Compression Drying

Recently, Ailanthus altissima wood has received increased attention in China. Although Ailanthus altissima has a number of advantages, such as fast-growing character and high density, the low dimensional stability is a restraining factor. Chemical modification could be a feasible way to overcome such drawbacks. The aim of this research was to study the physical and chemical properties of Ailanthus altissima veneers treated by urea-formaldehyde pre-polymer impregnation and compression drying. The results showed that this approach not only significantly increased the dimensional stability of wood, but also enhanced the bending strength and compressive strength parallel to the grain. The FT-IR analysis showed that the intensity of hydroxyl (-OH) and carbonyl (C=O) absorption peaks decreased, which indicated that the NH-CH2-OH of the pre-polymer reacted with the wood’s carboxyl and hydroxyl groups. The positions of the XRD peaks did not change, which indicated that the structure of cellulose crystallinity was not noticeably affected by the chemical modification. The TGA showed that the thermal stability of modified wood was improved, while FESEM showed that the wood cell wall and vessels were impregnated with chemicals.

Out-of-plane behaviour of unreinforced masonry strengthened using ferrocement overlay

Given the low tensile strength of unreinforced masonry (URM) walls, they are prone to out-of-plane failure, leading to eventual collapse of masonry buildings. In India and several other countries, seismic strengthening of URM buildings often utilizes ferrocement (welded wire mesh with micro-concrete or cement mortar). This study aims to investigate the efficacy of this technique in enhancing flexural capacity of URM walls in out-of-plane action. Six URM panels and 12 strengthened panels are subjected to flexural strength test, parallel and perpendicular to bed-joints. The effect of strengthening on common parameters, pertaining to out-of-plane flexural behaviour of ferrocement–URM composite walls, including failure modes, flexural strength, and modulus of rupture, is investigated. The experimental results are compared with analytical results obtained using ordinary beam theory. The results show that the URM panels exhibit sudden brittle failure whilst strengthened panels failed in a ductile fashion and exhibited a significant increase in the flexural strength. Further, the ordinary beam theory is able to predict the experimental results with reasonable accuracy.

Conventional compressive strength parallel to the grain and mechanical resistance of wood against pin penetration and microdrilling established by in-situ semidestructive devices

This paper compares semidestructive and destructive wood testing methods. The semidestructive methods used were pin pushing, screw withdrawal, dynamic pin penetration, microdrilling, and a new construction of a diagnostic device for an in situ timber assessment based on the principle of measuring the conventional strength by means of a small size loading jack in a drilled radial hole of 12 mm in diameter. To examine the differences between the methods, we conducted measurements using four softwood beams, 1–2 m long. The aim was to discern the variability of properties caused by the distribution of structural properties along the radius and the length of beams incorporated in historical constructions of trusses. The accuracy of the prediction of mechanical properties as measured by semidestructive devices was verified using correlations with mechanical properties as established by standard tests in compliance with EU standards. The test results show a very good correlation of conventional strength with wood density and strength established in standard samples in compression parallel to the grain.

A two-variable model for predicting the effects of moisture content and density on compressive strength parallel to the grain for moso bamboo

It is well known that mechanical performances of bamboos are significantly affected by moisture content (MC) and specific density. However, until now, no published studies have attempted to combine these two factors into one predictive model. In this paper, a two-variable model for predicting the combined effects of MC and specific density on compressive strength parallel to the grain (CSP) for moso bamboo was established and validated. The results show that the two-variable model is capable of predicting the CSP for bamboos of variable density and MC with significantly higher accuracy than either of the single-variable models. It is envisioned that this model could play an important role in supporting non-destructive evaluations of bamboos mechanical properties, greatly enhancing the potential applications of bamboo-based engineered products in commercial fields.

인도네시아산 주요 조림 및 유망 수종의 물리적 및 역학적 특성(I)

인도네시아산 주요 조림수종(Albizia, Gmelina, Mangium)과 유망수종(Durian, Gandaria, Jengkol, Kupa, Mangga, Nangka, Rambutan)의 밀도, 수축률, 종압축강도와 경도 등 물리적 및 역학적 특성을 조사하였다. 그 결과, Mangium, Gandaria와 Rambutan은 높은 밀도를, Albizia, Durian과 Jengkol은 낮은 밀도를 보였다. 공시재료 중 Mangium, Gandaria와 Mangga의 수축률은 다른 수종에 비해 작았으며, Albizia, Jengkol과 Rambutan의 수축률은 다른 수종에 비해 높았다. 이방도(T/R)는 Albizia, Kupa와 Mangga가 낮았고, Gmelina, Durian과 Jengkol이 다른 수종에 비해 높았다. Mangium과 Nangka는 종압축강도와 경도가 높았으며, Durian, Jengkol과 Mangga는 낮은 종압축강도를, Albizia와 Gmelina는 낮은 경도를 보였다. 10수종 중 Albizia, Durian, Jenkol, Mangga의 4수종을 제외한 6수종의 물리적 및 역학적 성질은 비교적 우수한 것으로 판단되었다. 본 실험의 결과는 인도네시아산 조림목의 효율적인 이용 및 장래 조림을 위한 유용한 기초자료로 활용될 수 있을 것이라 생각된다. The physical and mechanical characteristics of 10 Indonesian wood species were investigated. Mangium, Gandaria and Rambutan showed higher density. Mangium, Gandaria and Mangga appeared lower in shrinkage, and the ratio of tangential/radial was low in Albizia, Kupa and Mangga. The compression strength parallel to the grain and hardness were high in Mangium and Nangka. Gmelina, Mangium, Gandaria, Kupa, Nangka and Rambutan had valuable properties for commercial wood materials. Consequently, it is considered that the results of this study could be useful basic data for the improved use of planted and promising species in Indonesia.

Análise termomecânica da madeira de Corymbia citriodora submetida a gradientes térmicos

A madeira, quando exposta a condições de estresse, como no caso de um gradiente de temperatura, pode levar a estrutura de uma determinada instalação ao desmoronamento. A taxa na qual a madeira se converte em carvão é determinante, em função da redução da seção resistente. A presente investigação teve como objetivo avaliar o comportamento termomecânico da madeira de Corymbia citriodora submetida a gradientes de temperatura e diferentes tempos de exposição, com diferentes tratamentos (Verniz e CCB), com o intuito de minimizar o processo de carbonização. No que diz respeito aos ensaios mecânicos, pode-se afirmar que o aumento da temperatura de carbonização e do tempo de exposição das amostras ocasionou um decréscimo da resistência à compressão paralelamente às fibras do material, ocasionado fragilidade de carregamento. Os tratamentos testados (CCB e Verniz) não apresentaram resultados satisfatórios no que diz respeito ao retardo da combustão, não sendo, portanto, recomendáveis para esses fins.

Determination of Some Physical Attributes for Wooden Construction Elements Strengthened with Woven Wire Fiberglass

This study designed composite wooden construction elements strengthened with woven wire fiberglass netting and determined the technical attributes. Scots pine (Pinus sylvestris L.) was used in wooden layers, and woven wire fiberglass netting was used in intermediate layers. Layers were pressed with polyvinyl acetate (PVAc) D3 and Desmodur-VTKA adhesives to form 7 solid 13-layer laminated composite specimens. Experiments on 95 specimens determined density, bonding strength, bending resistance, and compression strength; solid and solid laminated wooden materials were tested and compared. BS EN 204 and BS EN 205 standards were complied with for bonding strength tests, TS 5497 EN 408 was used for densities, and TS 549 EN 408 was followed for bending resistance and compressive strength. Most factors, except for intermediate layer material in compressive strength and bending resistance tests perpendicular to the glue line, did not cause significant differences. Variables (adhesive, intermediate layer material) used for determining bending strength parallel to the glue line were effective. Polyurethane adhesive increased resistance to bending parallel to the glue line. These composite wooden construction elements supported with woven wire fiberglass netting could be advantageous for applications that require high bending resistance perpendicular to the glue line. However, these composites do not hold a compressive strength advantage.

On the effectiveness of lateral excitation of shear modes in AlN layered resonators

We describe the fabrication and frequency characterization of different structures intended for the lateral excitation of shear modes in AlN c-axis-oriented films. AlN films are deposited on moderately doped silicon substrates covered either with partially metallic or fully insulating Bragg mirrors, and on insulating glass plates covered with insulating acoustic reflectors. TiOx seed layers are used to promote the growth of highly c-axis oriented AlN films, which is confirmed by XRD and SAW measurements. The excitation of the resonant modes is achieved through coplanar Mo electrodes of different geometries defined on top of the AlN films. All the structures analyzed display a clear longitudinal mode travelling at 11,000m/s, whose excitation is attributed to the direction of the electric field (parallel to the c-axis) below the electrodes; this is enhanced when a conductive plane (metallic layer or Si substrate) is present under the piezoelectric layer. Conversely, only a weak shear resonance (6,350m/s) is stimulated through the effect of coplanar electrodes, which is explained by the weakness of the electric field strength parallel to the surface between the electrodes. A significantly more effective excitation of shear modes can be achieved by normal excitation of AlN films with tilted c-axis.

An artificial neural network model for predicting compression strength of heat treated woods and comparison with a multiple linear regression model

This paper aims to design an artificial neural network model to predict compression strength parallel to grain of heat treated woods, without doing comprehensive experiments. In this study, the artificial neural network results were also compared with multiple linear regression results. The results indicated that artificial neural network model provided better prediction results compared to the multiple linear regression model. Thanks to the results of this study, strength properties of heat treated woods can be determined in a short period of time with low error rates so that usability of such wood species for structural purposes can be better understood.

Physical and Mechanical Properties of Paricá Wood Species Treated with CCB Preservative

Wood of Parica species (Schizolobium amazonicum) is highly susceptible to degradation by decay microorganisms. Due to its increasing production in the northern region of Brazil, about 85 thousand hectares, and later use both for structural purposes and for the furniture industry, the need of extending life of Parica wood applying chemical preservatives arises. One current alternative is the treatment by autoclave using CCB (Copper Chrome Boron). The aim of this study was to evaluate the influence of treatment with CCB in the properties: apparent density, parallel and perpendicular hardness to the grain, strength to shear and in the compression parallel to the grain of the Schizolobium amazonicum wood species, comparing the results with untreated wood. We observed that treatment with CCB did not change the properties of apparent density, shear strength, perpendicular hardness, strength and stiffness in compression parallel to the grain. For the hardness strength parallel to the grain was decreased in 28.9%.

Comparação entre valores de ensaios experimentais e calculados da resistência ao embutimento da madeira de Pinus taeda L.

Para dimensionar ligações entre membros estruturais de madeira com pinos metálicos (pregos ou parafusos), dois fenômenos devem ser levados em consideração: a flexão do pino metálico e a resistência da madeira ao embutimento. A norma brasileira ABNT NBR 7190:1997 preconiza a metodologia empregada em ensaios laboratoriais para determinação da resistência da madeira ao embutimento com pino metálico e, na ausência dos ensaios, especifica relações para estimar a resistência da madeira ao embutimento a partir da resistência na compressão. O objetivo desta pesquisa consistiu na comparação entre valores de resistência ao embutimento da madeira determinados experimentalmente e calculados utilizando parâmetros recomendados pela ABNT NBR 7190:1997. Pelos resultados dos testes de hipótese, pode-se concluir que a estimativa da resistência ao embutimento paralelo às fibras proposta pela ABNT NBR 7190:1997, que estabelece equivalência com os resultados de compressão na mesma direção, mostrou-se precisa para as madeiras de Pinus taeda L.. Entretanto, o mesmo não foi observado na direção normal em relação às fibras, possivelmente explicada pelo valor do coeficiente áe presente na equação para o cálculo de fe90.