Rupture In Bending Research Articles

INFLUENCE OF SITES ON THE PHYSICAL AND MECHANICAL PROPERTIES OF NATIVE TROPICAL WOODS

The Amazon rainforest displays wide ecological diversity, reflected in its wood variation. The study evaluated the influence of different locations on the properties of wood from native tropical species extracted from the Brazilian Amazon. The most frequent species in the locations were selected, and a total of 104 trees were extracted. The logs were sawed breakdown to make beams (50 × 110 × 2,000 mm). The wood density and mechanical resistance of these samples were determined. The wood density ranged of 0.25-1.00 g/cm3, modulus of elasticity and rupture in static bending ranged of 5,982-19,025 MPa and 35-204 MPa, respectively. For compressive strength parallel to the grain, the range was 24-111 MPa; the strength of wood compressed parallel was 20-245 MPa, and the shear strength was 50-245 MPa. The study detected differences in the physical and mechanical properties of the woods regarding the origin of the sites (Amazonas-Pará/Brazil), with the modulus of elasticity and the wood density showing the greatest variations.

Elasto-mechanical properties of thermo-hygro-mechanical (THM) densified oil palm sawn timber

ABSTRACT Oil palm wood is mainly low in density and since strength and stiffness correlate with density, this study aimed to enhance the properties of oil palm wood through thermo-hygro-mechanical (THM) densification. In contrast to other studies using small laboratory-sized specimens, this study examined the densification of oil palm boards in sawn timber dimensions of 2.0 m length. Modulus of elasticity (MOE) and modulus of rupture (MOR) in bending, shear strength and shear modulus parallel by two-plate shear test and Young’s modulus in the three main directions as well as shear modulus in the three planes by ultrasonic testing were determined at densified and undensified specimens. The bending properties were increased to considerably higher levels and a compression ratio of 60% showed higher MOE and MOR values than that of 40%; whereas for boards of the inner part of the trunk, a compression ratio of 60% showed better results than that of 75%. The shear properties were only slightly increased through densification. Densification can improve the properties of oil palm wood. However, the wide range of density and properties found in natural oil palm wood is also present in densified oil palm wood.

Optimization of parameters for vacuum heat modification of Cupressus funebris wood

A full factorial experiment was conducted to analyze the main and interaction effects on the physical and mechanical properties of Cupressus funebris Endl. wood subjected to vacuum heat modification. The response variables evaluated were mass loss rate (ML, %), moisture resistance (MR, %), and modulus of rupture in bending (MOR, MPa). The results reveal significant variations in the effects of modification time, holding temperature, and vacuum pressure as independent factors, along with varying degrees of interaction effects among them. Simplifying the analysis model, a regression equation was derived to describe the relationship between the response variable (mass loss rate) and the factors: The model achieved an R-squared value of 96.0% and an R-squared (predicted) value of 73.7%, indicating good overall predictive performance. Optimal process parameters for mid-temperature vacuum heat modification of cypress were determined based on the mass loss rate and modulus of rupture (MOR), resulting in a modification temperature of 120 °C, holding time of 5 h, and a pressure intensity of 0.1. The reliability of the full factorial experiment was further confirmed through orthogonal testing.

Effect of Primary Spruce Lamella Aging on the Bending Characteristics of Glulam Beams

Glued laminated (glulam) beams are used in the roofs, ceilings and walls of buildings as well as in bridges and towers. At present, with the limitation of tree harvesting, the production of glulam beams from recycled wood sources is implemented with the proviso that their mechanical properties and resistance to pests, fire and weathering will not be aggravated. This work deals with the primary effect of aging Norway spruce wood (Picea abies Karst. L.) lamellas on the moduli of rupture (MOR) and elasticity (MOE) in bending of three-layer glulam beams composed of sound and aged lamellas and polyurethane (PUR) glue. Three methods of lamella aging were used: (A) natural, lasting 60 years in the form of roof trusses with a greater or lesser degree of bio-attack by woodworm (Anobium punctatum De Geer); (B) artificial, caused by increased temperatures from 160 to 220 °C for 4 h; (C) artificial, caused by 2% water solutions of inorganic preservatives, namely, CuSO4 × 5H2O, ZnCl2, H3BO3 or (NH4)2SO4, for 28 days. The lowest MOR values were determined for glulam beams in which all three lamellas or two surface lamellas had a greater degree of bio-attack (60.5 MPa, a decrease of 25.9%) or were exposed to primary aging at 220 °C (62.6 MPa, a decrease of 23.3%). On the contrary, the exposure of lamellas to 160 or 180 °C did not significantly influence the MOR of beams (76.0–82.7 MPa, an average decrease of 1.6%). The MOE of glulam beams ranged from 7540 to 10,432 MPa without an obvious influence of the method of lamella aging or their location in the beams. Linear correlations between the MOR or MOE of glulam beams and the shear strength (σ) of glued joints, if both composite types consisted of similarly aged lamellas, were only slightly significant or insignificant.

Performance of binderless board manufactured using camphor tree residue

Residue of the branch wood of camphor tree (Cinnamomum camphora) was used to manufacture binder-free biodegradable biomass fiberboard (bio-board) by the wet method. To investigate the mechanical properties of the bio-board, bending rupture stress and tensile rupture stress tests were measured and the effect of heating temperature and applied pressure on the performance of the bio-board was evaluated. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the influencing factors on the microstructure and bond quality of the bio-boards. The overall density of the bio-boards exceeded 0.8 g/cm3 and the moisture content was below 10%, which conformed to the JIS A 5908 standard (2014) for the hardboard S20 type design specification. The bending rupture stress and tensile rupture stress continued to increase, and the dimensional stability continuously improved as the applied pressure and the heating temperature increased. However, when the heating temperature exceeded 170 °C, the increase in the rupture stress slowed down and the dimensional stability had been improved. Furthermore, increasing the heating temperature was more conducive for optimizing the bio-board’s performance than increasing the applied pressure.

Bending behavior of engineered cementitious composites (ECC) with different recycled and virgin polymer fibers

This study evaluated Engineered Cementitious Composites (ECC) with polyvinyl alcohol (PVA), polypropylene (PP) or recycled polyester (POL) fibers inserted in a matrix with elevated silica fume content. Several PP (2.2–2.6%) and POL (2.3–2.7%) contents were tested and compared to a compound containing 2.0% PVA. Flexural bending strength tests, the bending rupture modulus, number and width of cracks and deformation were measured at 5 different curing ages (7, 14, 28, 56 e 84 days). The test results also showed that in the fresh state, ECCPVA2.0 presented the best result with an average spread of 255 mm, followed by ECCPP2.4 and ECCPOL2.3. All Γ values obtained confirmed that all composites attained plastic consistency. In the hardened state, composites with POL fibers had tensile strength performance similar to PVA fibers with regards to deformation, deflection, rupture modulus, average crack width and number of cracks. In addition, ECCPOL2.7 demonstrated mechanical properties superior to ECCPVA2.0. So, the use of 2.7% POL content resulted in strengths higher than the reference PVA compound and demonstrated the potential of POL fibers in ECC development at ages over 28 days. The use of recycled POL fibers, at a content of 2.7%, resulted in an increase in the ductility of the composite, reaching the values of ECC-PVA at 28 and 84 days. On the other hand, PP composites did not present the expected behavior of an ECC. More specifically, the matrix had high tensile strength, modulus of elasticity and tenacity, which limited crack formation and overloaded the reinforcement fibers. Thus, PP fibers were deemed incompatible for ECCs with rich matrices.

Development of a 3D finite element model at mesoscale for the crushing of unidirectional composites: Application to plates crushing

This paper presents the development of a new 3D finite element model for the simulation of UD composites materials under crushing, at the mesoscale. It is based on the Discrete Ply Model (DPM), enhanced with a new damage law to represent compression at constant stress due to localised crushing and its propagation from one element to another. The model aims to take into account the various damage types involved in UD laminates during crushing and the associated absorbed energies: delamination, splitting, ply rupture in tension or bending, compression due to localised fragmentation and friction. The model is confronted with experimental results obtained on laminated plates crushing: not only global metrics (force, energy absorbed…) but especially key morphological aspects of the crushing front (delamination lengths, splaying, number of plies under localised crushing, debris wedge…) thanks to high speed camera pictures.

Particleboards from Recycled Pallets

Worldwide production of wooden pallets continually increases, and therefore in future higher number of damaged pallets need to be recycled. One way to conveniently recycle pallets is their use for the production of particleboards (PBs). The 3-layer PBs, bonded with urea-formaldehyde (UF) resin, were prepared in laboratory conditions using particles from fresh spruce logs (FSL) and recycled spruce pallets (RSP) in mutual weight ratios of 100:0, 80:20, 50:50 and 0:100. Particles from RSP did not affect the moisture properties of PBs, i.e., the thickness swelling (TS) and water absorption (WA). The mechanical properties of PBs based on particles from RSP significantly worsened: the modulus of rupture (MOR) in bending from 14.6 MPa up to 10 MPa, the modulus of elasticity (MOE) in bending from 2616 MPa up to 2012 MPa, and the internal bond (IB) from 0.79 MPa up to 0.61 MPa. Particles from RSP had only a slight negative effect on the decay resistance of PBs to the brown-rot fungus Serpula lacrymans, while their presence in surfaces of PBs did not affect the growth activity of moulds at all.

Thermal and mechanical characterization of blindex glass powder residue® for the production of ecological coating

The science of materials has great interest in the development of new composites, therefore, this work aims to obtain a new material using the waste produced by the industries themselves and which in many cases produce a serious problem for the environment. For the development of this research, was used the residue in the form of mud resulting from the cutting process in the manufacture of flat glazing. The samples obtained dehydrated for 24 h at a temperature of 100 °C. The samples were pressed using hydraulic press with a capacity of 150 ton/cm2 resulting in proof body's with dimensions in the order of 105 mm long, 52 mm wide and 5.7 mm thick and submitted the process of sintering at different temperatures in ambient atmosphere. The characterizations of proof bodies applying thermal analysis technique (TGA), presented evaporation of surface H2O and to the degradation of the molecules of Na2O, K2O and P2O5 until 100 °C. In the range between 200 °C and 600 °C the curve has a more linear attributed to the thermal degradation of the Al2O3, MgO and Fe2O3 molecules and a thermal stability above 600 °C. The x-ray diffraction analyses (XRD), with the precursor glass powder presented characteristic of a standard amorphous structure and with the powders of sintered proof body's at different temperatures, observed the characteristic peaks of calcite (CaCo3), cristobalite (SiO2), quartz (SiO2) and low silicon oxide (SiO2) crystals. The characterizations using scanning electron microscopy technique (SEM) show a homogeneous distribution of particles with sizes in the order of 30 μm. The mechanical characterizations in the specimens applying bending rupture tests showed range of rupture modules of the 31.92 kgf/cm2 and 55.28 kgf/cm2 to the range temperature between 200 °C and 600 °C. The characterizations and water absorption tests apresented that there is a great advantage in the use of blindex® glass powder residue for the manufacture of a new ecological coating, this material can be applied more abrasively to paving blocks, septic sewer tanks, grease traps, wall building blocks and in the most finished form it can be applied as a tactile floor, internal coatings in the form of tablets for bathroom and kitchen and other finishes to the civil construction sector.

Effect of Thermal Modification Treatment on Some Physical and Mechanical Properties of Pinus oocarpa Wood

This study deals with the effect of heat treatment on Pinus oocarpa specimens from forest plantations in Colombia. The effects of two heat treatments at 170 and 190 °C for 2.5 h in saturated vapor were evaluated based on the color, dimensional stability, air-dry and basic densities, modulus of elasticity (MOE), and modulus of rupture (MOR) in static bending of samples. The evaluations were carried out following the Colombian Technical Standards NTC 290 and 663, and the color changes resulting from heat treatments were monitored using the CIE-Lab, as well as other standards from the literature. The results show that there was 2.4% and 3.3% mass loss of wood modified at 170 and 190 °C, respectively. The air-dry and basic densities were higher in 170 °C treatment than after 190 °C treatment, and the thermal modifications applied increased the dimensional stability of the treated wood. After treatment at 170 and 190 °C, the lightness to darkness (L*) was reduced by 10% and 22%; the a* coordinate increased by 11% and 26%, causing redness in the treated wood; the b* coordinate increased by 14% and 17%; and the values of the wood color saturation (c*) increased by 14% and 18%, respectively. The general color change (ΔE*) increased gradually with the increase in the treatment temperature, resulting in a high color change to a very different color. The bending strength of thermally modified wood was improved and significantly increased to values higher than those of unmodified Pinus oocarpa wood. The high air-dry and basic densities, improved dimensional stability and resistance to bending, and attractive appearance of the treated wood indicate that thermal modification is a promising alternative for the transformation of Pinus oocarpa wood into a raw material with a high added value.

Particleboards from Recycled Wood

The effective recovery of wood waste generated in wood processing and also at the end of wood product life is important from environmental and economic points of view. In a laboratory, 16 mm-thick three-layer urea–formaldehyde (UF)-bonded particleboards (PBs) were produced at 5.8 MPa and 240 °C and with an 8 s/mm pressing factor, using wood particles prepared from (1) fresh spruce wood (C), (2) a mixture of several recycled wood products (R1), and (3) recycled faulty PBs bonded with UF resin (R2). Particles from spruce wood were combined with particles from R1 or R2 recyclates in weight ratios of 100:0, 80:20, 50:50 and 0:100. In comparison to the control spruce PB, the PBs containing the R1 recyclate from old wood products were characterized by lower thickness swelling after 2 and 24 h (TS-2h and TS-24h), lower by 18 and 31%; water absorption after 2 and 24 h (WA-2h and WA-24h), lower by 33 and 28%; modulus of rupture in bending (MOR), lower by 28%; modulus of elasticity in bending (MOE), lower by 18%; internal bond (IB), lower by 33%; and resistance to decay determined by the mass loss under the action of the brown-rot fungus Coniophora puteana (Δm), lower by 32%. The PBs containing the R2 recyclate from faulty PBs were also characterized by a lower TS-2h and TS-24h, lower by 45% and 59%; WA-2h and WA-24h, lower by 61% and 51%; MOR, lower by 37%; MOE, lower by 17%; and IB, lower by 33%; however, their biological resistance to C. puteana was more effective, with a decreased Δm in the decay test, lower by 44%.

Properties relationship evaluation and plasticity analytical model approach for Brazilian tropical species

In anisotropic materials such as wood, different responses to bending induced stresses could be expected. This study evaluated the behavior of properties of modulus of rupture (MOR) in bending, the tension strength parallel to grain and the compression strength parallel to grain of Brazilian tropical hardwood species in accordance with Brazilian, European and International Standards, and an analytical equation considering plasticity in the compressed region. Experimental data were obtained using clear wood specimens and tests on ten species. An analysis of the mechanical behavior was conduced for three strength relationships: bending to compression, bending to tension and tension to compression. Linear regression models were determined using the 5th percentile and compared to the ones found by the standards cited. The experimental results were also evaluated to an analytical equation modified from the moment equilibrium of a cross-section. Of the equations evaluated in this study, the ones suggested by the European and International standards for tension strength from bending strength were the ones which best estimated the 5th percentile on experimental data. Other relationships did not show a good agreement with the equations. The analytical equation used had a mean model error 37.4% higher than the experimental values for the prediction of the ratio of tension to bending strength.

Effect of thermo-hydro-mechanical densification on the wood properties of three short-rotation forest species in Costa Rica

Alnus acuminata, Vochysia ferruginea, and Vochysia guatemalensis are three low-density wood species used for reforestation in Costa Rica. The goal of this work was to study a thermo-hydro-mechanical densification process and test the characteristics of densified wood of these species. Twelve densifying treatments based on temperature, compression time, and use/no use of steam were tested. The variables of the densification process and the properties of the densified wood were determined. The results showed that the densification percentage was over 80% for wood of A. acuminata and over 70% for wood of V. ferruginea and V. guatemalensis. In the three species, the densification process was influenced by initial density. The influence of temperature during the densification process affected the heating rate and color change. An increase in the modulus of elasticity and modulus of rupture in static bending and in the hardness of the densified wood relative to the normal wood was observed, as well as a clear positive correlation of the properties with final density and maximum load, the latter being highly correlated with initial density. This showed that initial density was significant in the densification process and affects wood properties.

ESTIMATION OF WOOD TOUGHNESS IN BRAZILIAN TROPICAL TREE SPECIES

ABSTRACT Wood has been used for several purposes such as in civil and rural construction. Knowing wood mechanical behavior under short-term loading is essential for safer structural designs. However, wood toughness is a mechanical property little investigated for this purpose. Thus, this study aimed to evaluate, using exponential and polynomial regression models (linear, quadratic, and cubic), the possibility of estimating toughness as a function of apparent density, compression parallel to grain strength, and modulus of rupture in static bending. Thirty-six Brazilian tropical wood species from south of Roraima, Mato Grosso do Sul, and north and northeast of Mato Grosso were tested. Our results showed the significance and representativeness of all investigated fits, among which a cubic polynomial function is the most indicated for wood toughness estimates.

Characteristics of particleboard manufactured from bamboo shoot sheaths

This study emphasizes on the physical, mechanical, and thermal properties of single-layer particleboard manufactured from bamboo shoot sheaths. Particleboards were produced through the hot-pressed process and glued together by Diphenylmethane Diisocyanate (MDI) adhesive. This is in order for producing specified densities of boards as 400-kg, 600-kg, and 800-kg per m3. The raw material was sieved into four sizes: No.1-No.4 mesh. The particleboards were used to find board density, water absorption, thickness swelling, modulus of elasticity, modulus of rupture in bending, and internal bonding according to the JIS standard. Coefficients of thermal conductivity (k) of boards were discovered by a heat flow meter in steady-state conditions. The results showed that the particleboard performed outstandingly in terms of tensile strength perpendicular to the surface (internal bonding) and low thermal conductivity. However, there were some weaknesses found from their characteristics that were high water absorption and thickness of swelling, low modulus of elasticity and modulus of rupture comparing to standard criteria. The results also indicated that bamboo shoot sheaths, the agricultural residue, can be produced as particleboard, and are appropriate for an indoor heat insulator, but further investigation is required to improve the strength and durability of the particleboard.

Valorization of wood shavings waste for the production of wood particulate composites

The aim of this work was to evaluate the physical and mechanical properties of particleboards using particles from wood shaving at three urea-formaldehyde adhesive contents: 6, 9 and 12% (dry mass basis). The particleboards were produced with nominal density of 0.70 g.cm-3, pressing cycle with temperature of 160 °C, pressure of 3.92 MPa and time of 8 minutes. The properties of water absorption (WA), thickness swelling (TS), both after 2 and 24 hours, apparent density, compression ratio, perpendicular traction, modulus of elasticity (MOE) and modulus of rupture (MOR) in static bending, Janka hardness and screw withdrawal resistance were evaluated. The results of the tests indicated that with the increase of the adhesive content from 6 to 12%, there was no significant statistical difference for the average values of apparent density and compression ratio, being 0.621 g.cm-3 and 1.234, respectively, and the WA and the TS are decreased after 2 and 24 hours. There was a gain of 93% for the MOR property and 64% for the MOE property with the increase of the adhesive content. For perpendicular traction, the highest mean value was 0.67 MPa, referring to the panels with 12% of adhesive. For Janka hardness, the treatments with contents of 9 and 12% of adhesive presented the highest average values being of 21.60 and 25.26 MPa, respectively. In general, the use of wood shavings is feasible for the production of particleboards with a 12% adhesive content. Keywords: Mechanical resistance; Dimensional stability; Particleboards.

Non-biocide antifungal and anti-termite wood preservation treatments based on combinations of thermal modification with different chemical additives

The synergic effect between a mild chemical and thermal modification of beech wood (Fagus sylvatica) has been studied. A low concentration of additives based on vinylic-polyglycerol, vinylic-glycerol, and maleic anhydride was impregnated into beech wood, followed by curing under different temperature conditions at 103, 150, 200, and 220 °C. The modified wood was then analyzed for its leaching resistance, dimensional stability, wettability, modulus of elasticity (MOE) and modulus of rupture (MOR) in bending, decay resistance against Trametes versicolor, and termite resistance against Reticulitermes flavipes. Results have disclosed a synergic effect of thermo-chemical wood modification under 200 and 220 °C curing conditions. At these curing temperatures, thermo-chemically modified beech presents improved dimensional stability (> 60%) and better resistance against both Trametes versicolor and Reticulitermes flavipes compared to the control. However, at the same conditions, MOE and MOR values were lowered by approximately 25% and 60%, respectively.

Timber grading of Pinus uncinata , a lesser known pine species from the pyrenean mountain range

Timber grading is an essential step into the value process to determine wood usability for structural uses. It requires well-described characteristics obtained easily by taking non-destructive measurements to quantify reliable indicators of mechanical properties. In this paper we present an approach based on both timber scale and clear-wood scale measurements using the case of Mountain pine (Pinus uncinata). An important experimental plan have been performed from collected trees of French and Spain Pyrenean regions allowing significantly the use of inter-correlations between measurements. The physical properties of clear wood present an important adaptation of tree growth condition with a lower modulus of elasticity as a consequence of microstructure at cell-wall level but a conventional modulus or rupture in bending for pines. However, the results on timber presents an important the difference between visual and machine grading for this species in view of mechanical properties considered. The results obtained also show possible improvement and limitations of current regulation in the grading mountain pine timber for structural use.

Dynamic and static mechanical properties of Eucalyptus nitens thermally modified in an open and closed reactor system

Eucalyptus nitens is a fast growing plantation species that has a good acclimation in Chile. It is commonly used for pulp and paper, but there is a growing market for solid wood products made from this species and an interest on producing high quality material. Thermal modification technology have been used to obtain high quality product out of fast growing plantation species. In this study we modified Eucalyptus nitens to analyse the influences of the process conditions and evaluated its mechanical properties under several process conditions. The material was modified in a closed system under elevated pressure and controlled relative humidity (30 and 100% relative humidity) at temperatures between 150 and 170°C, and in an open system with a standard thermal modification procedure between 160 and 230°C. Modulus of elasticity, modulus of rupture, deflection and work in bending (in elastic and inelastic proportions) and the resistance to impact milling in high energy multiple impact tests were determined. Mass loss after each modification was also measured and correlated with the mechanical properties. Anatomical properties of selected modifications were analysed. There were no significant differences between open and closed system modifications in both mechanical and anatomical properties.

Effect of incorporating sludge from poultry slaughterhouse wastewater treatment system in ceramic mass for tile production

Abstract Brazil is one of the largest producers of red ceramic in the world and the main mass used in the manufacture of this product are composed exclusively of clay, which are extremely abundant in the Earth’s crust. Several studies in the literature consider the incorporation of small amounts of waste from different segments in the ceramic mass, usually at levels lower than 10%, due to the inertness of waste by ceramic processing. The western region of the State of Parana stands out in the production and processing of poultry meat, and this process in the slaughterhouses industry consumes a lot of water, and consequently generates effluents that require a specific treatment. Normally, the wastewater treatment system used for this activity is the process of physical–chemical flotation followed by tridecanters, which generates a considerable amount of sludge that also needs a proper disposal; it is often sent to outsourced companies to produce compost along with other organic materials, but with a high cost of transportation and destination for generating companies. Given this fact, seeking viable alternatives to the use of this type of sludge generated in the poultry slaughterhouse wastewater treatment system, it was proposed a study to evaluate, on a laboratory scale, the technical feasibility of incorporating it in ceramic mass intended for manufacturing tiles. Low concentrations of sludge generated by the slaughterhouses have been included in a mass industrially used for the manufacture of ceramic tiles and the performance of the mixtures was evaluated compared to a reference mass, without inclusion of waste. The specimens prepared with such formulations were tested for bulk density, linear drying and firing shrinkage, bending rupture stress, efflorescence formation and the behavior of mixture during firing was evaluated by vitrification curves. The results indicate that incorporation of 2% (w / w) sludge in the ceramic mass did not significantly alter the properties of the material, being even possible to reduce the consumption of fuel in burning, since the inclusion of such organic matter into the mass contribute to heat generation, since the combustion of the material is an exothermic reaction.