Janka Hardness Research Articles

PRODUCTION OF MDP PANELS WITH YERBA MATE HARVEST RESIDUES

The quality of MDP panels produced with Pinus taeda wood particles mixed with yerba mate harvest residues was evaluated. Monolayer panels were produced with the addition of 0. 20. 40. 60. 80 and 100% proportion of yerba mate waste, with a nominal specific gravity of 0.65 g.cm-³, using 12% urea-formaldehyde resin, 0.5% paraffin and 2% ammonium sulfate catalyst. The panels were pressed for 10 minutes at a temperature of 140°C and pressure of 40 kgf/cm². The physical properties of apparent density, moisture content, water absorption and thickness swelling (2 and 24 hours) were evaluated, as well as the mechanical properties of static bending (MOR and MOE), internal bonding, screw withdrawal on the face and Janka hardness. There was a trend towards an increase in internal bonding with an increase in the proportion of yerba mate residue in the panels, but the opposite occurred for the other mechanical properties studied. Some physical properties such as water absorption and thickness swelling resulted in better performance when yerba mate particles were added. In view of this, it can be concluded that it is possible to produce panels with the addition of yerba mate up to 40% in the composition with yerba mate particles, without affecting the quality of the properties.

Study on Mechanical Properties of Moso Bamboo in Jian'ou City, Fujian Province, China

The original bamboo material of 3 to 4-year-old moso bamboo in Jian'o City, Fujian Province, was used as the research object. Study the change of mechanical properties such as axial compressive strength, bending strength, tensile strength, shear strength, and hardness test. The main work and results of this paper include:Forty-five longitudinal compression specimens on moso bamboo tubes were tested to investigate the effects of different sizes and bamboo knots on the axial compressive strength of the moso bamboo tubes. The mean tensile strength of moso bamboo was found to be 165.13 N/㎟. A total of 27 shear specimens of 5cm moso bamboo tubes were tested, and their average shear strength was 2.61Mpa; he average flexural strength of moso bamboo was 172.48N/㎟. The hardness of moso bamboo specimens was tested using the Janka hardness method. The hardness of each part of Moso bamboo was significantly different.Comparing the mechanical properties of moso bamboo with other wood timber, moso bamboo showed better mechanical properties, the research hoped to provide a theoretical basis and scientific evidence for a comprehensive understanding of the complex mechanical properties of Fujian moso bamboo and the use of moso bamboo in high value-added applications.

Wood Quality of Young Tectona grandis L. f. Trees and Its Relationship with Genetic Material and Planting Site in Mato Grosso, Brazil

Tectona grandis L. f. (teak) is highly valued in the international market, but its volume and properties vary depending on its genetic material and planting site. Evaluating these factors is crucial for promoting new plantations. Therefore, this study aimed to assess the impact of genetic material (clones TG1 and TG3 and seminal material) and planting site (Nova Maringá and Água Boa, Mato Grosso, Brazil) on morphological parameters (heartwood, sapwood, bark, pith proportions, and pith eccentricity), physical properties (shrinkage and air-dry density), and mechanical properties (static bending strength—fm, compressive strength—fc0, Janka hardness—fH90, and shear strength—fv0). For this purpose, we sampled five trees aged 13 years per genetic material from commercial plantations. In Nova Maringá, trees exhibited, on average, 56.07% heartwood, while in Água Boa, this value was less than 50%. Seminal material showed the lowest percentage of heartwood (49.2%). The pith percentage was significantly greater in Água Boa than in Nova Maringá, regardless of the genetic material. We observed the highest standard deviation (5.61) in pith eccentricity for the seminal material. Both the planting site and genetic material influenced the air-dry density (~12% moisture content), which ranged from 0.535 to 0.618 g·cm−3. Trees grown in Nova Maringá produced wood with higher dimensional stability than those from Água Boa, exhibiting a 14% lower radial shrinkage and a 6% lower volumetric variation. In Nova Maringá, the wood from the seminal material exhibited greater resistance. On the other hand, in Água Boa, that material showed lower resistance (fv0, fm, and fc0), or there was no significant difference (fH90) compared to the clonal materials. When comparing the clonal materials (TG1 and TG3) at each planting site, they demonstrated similar mechanical properties. The variability in physical and mechanical properties among different genetic materials and planting locations highlights the need to select appropriate teak genetic materials for each region. We concluded that more productive teak clones can be selected without compromising the physical and mechanical properties of the wood.

Characterization of fly ash reinforced wood polypropylene composites

In this study, fly ash, which is released as waste from thermal power plants and has negative effects on the environment, was evaluated as a filler in wood-plastic composite materials (WPC). For this purpose, inorganic fly ash from thermal power plants was mixed with polypropylene (PP) thermoplastic polymer at 10%, 20%, 30%, 40%, and 50% by extrusion method instead of wood flour used in wood plastic composite materials. Maleic anhydride-treated polypropylene (MAPP) was used to strengthen the bonding during WPC production. The material mixed in extrusion was passed through a crusher and turned into pellets. Test samples were prepared using injection molding of pelletized WPC material. Density, thickness swelling, water absorption, modulus of rupture, impact strength, modulus of elasticity in bending, tensile strength, janka hardness, differential scanning calorimetry (DSC), and thermogravimetric analyses (TGA) were performed on the prepared test samples. The results indicated that as the amount of fly ash used in the wood-plastic composite material increases, the density increases but the thermal degradation temperature of the material, water uptake, the swelling ratio to its thickness, tensile strength, impact strength, janka hardness, modulus of rupture, and modulus of elasticity decrease.

Influences of oak utilization on the medium density fiberboard properties

Softwoods are the basic and traditional raw materials for medium-density fiberboard production. However, sustainable consumption of wood material in the production of wood-based products requires material variety. Therefore, the usability of hardwood species in the production and its effects on the board properties should be of interest. Considering this, the influence of oak utilization percentages (30 %, 50 %, 70 %, and 100 %) on the physical (density, thickness swelling-TS 2 and 24 h) and mechanical (modulus of rupture, modulus of elasticity, internal bonding, screw holding resistance, and Janka hardness) properties of medium density fiberboard was evaluated in this study. Boards were factory-made instead of laboratory-made using Quercus petraea (oak), Fagus orientalis (beech), and Pinus sylvester (Scots pine) fibers. According to the results, the modulus of rupture, modulus of elasticity, and Janka hardness values were increased when medium-density fiberboard was produced using only oak fiber. On the contrary, thickness swelling, screw-holding resistance, and internal bonding properties were decreased.

Decay resistance and dimensional stability of wood impregnated with castor oil using a pressure treatment

Abstract This study was conducted to investigate the uptake of castor oil (CAO) in some wood specimens and the effect of CAO on the leaching ability, dimensional stability and fungal-decay resistance of the wood specimens. CAO was infused into the specimens using a pressure treatment. Uptakes of CAO penetrated in yellow poplar (YEP), Japanese cedar (JAC) and Douglas fir (DOF) blocks were higher than 100 %. The leaching ability of the CAO-based suspensions against saline water was the lowest in YEP, followed by Japanese larch (LAR), JAC and DOF. The retention values were 90 % or higher in most of the specimens. Radial and tangential swellings of CAO-treated strips submerged in saline water for 2 weeks were restrained compared to control specimens. No significant differences were found between bending strength and Janka hardness of CAO-treated and control strips. CAO treatment provided acceptable decay resistance to most wood specimens against Fomitopsis palustris and Trametes versicolor. Retention of CAO in the leached strips were identified through X-ray microscopic observation. Based on the results, CAO was determined to be an effective agent for improving the dimensional stability of wood. These results demonstrate the great potential of CAO as an environmentally friendly wood preservative and dimensional stabilizer, allowing CAO-permeated wood as raw materials for both indoor and outdoor use.

Use of Carbon and Basalt Fibers with Adhesives to Improve Physical and Mechanical Properties of Laminated Veneer Lumber

Climate change is one of the main factors influencing the research of environmentally friendly materials. This is why the use of engineering fibers as a reinforcement technique in wood, in order to increase its mechanical properties, has recently been investigated. This research presents the results obtained from the use of carbon and basalt fiber fabrics as a reinforcement for microlaminated Radiata Pine wood panels at a laboratory scale using the adhesives epoxy resin and polyvinyl acetate. Tests were carried out in comparison to the control boards, relating the physical properties obtained in terms of thickness swelling by 48 h-water immersion with a decrease of 19% for the polyvinyl acetate and carbon fiber matrix reinforcement, about the mechanical properties evaluated, a better performance was obtained for the epoxy resin and carbon fiber matrix reinforcement and in terms of flexural stiffness and strength (in flatwise), tensile strength and Janka hardness, with an increment of 31%, 38%, 56% and 41%, respectively.

Quality of Tectona grandis for sawn wood production

Forestry companies have invested in genetic improvement to increase wood production in a shorter amount of time. Thus, studies are needed to compare the properties of clonal and seminal wood materials. The objective of this study was to analyze physical and mechanical properties of Tectona grandis from clonal (C1 and C2) and seminal (S) origin and evaluate the yield and quality of sawn wood subjected to outdoor and oven drying. Genetic material was collected from six, 15-year-old trees. Clone C2 presented the lowest amount of bark, and 51 % heartwood up to half the commercial height, while the heartwood of C1 and S went up to 25 % of the height. The three materials did not differ statistically for maximum angular deviation, pith eccentricity, basic density, Janka hardness, anisotropy, commercial income of sawn wood and the presence of knots. After the drying processes, the bowing and crooking indexes were less than 5 mm.m-1, however, the seminal material showed a higher cracking incidence after outdoor and oven drying. In conclusion, the wood properties of the three materials are similar. In addition, the oven drying process is recommended.

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.

Impact of thermal modification on swelling and mechanical behavior of Couratari spp.

Thermal modification mechanisms and their effects on physical and mechanical properties of native Amazon hardwoods are not yet completely understood. It is expected that such treatments can improve the properties of low-value Amazonian woods and sapwood residues. This study aimed to investigate the impact of heat treatment on the swelling and mechanical properties (strength and stiffness to Static Bending and Janka hardness) of tauari wood (Couratari spp.), a low-value Amazonian hardwood. For this, tauari wood samples were thermally modified in an electric oven under hot air irradiation at final temperatures of 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, and 210 °C for 2.5 h. The main results showed that thermal modification increased the hydrophobicity of tauari wood without any noticeable effects on the mechanical behavior of the wood up to 200 °C. It was stated that up to 200 °C thermal modification is beneficial in terms of gains in hydrophobicity. In contrast, above 200 °C, despite an increase in hydrophobicity, consistent decreases in strength (MOR) and hardness were observed.

Physico-Mechanical Properties of Waterlogged Archaeological Wood: The Case of a Charred Medieval Shipwreck

In 2008, a late-12th-century merchant ship was discovered off the commercial port of Rhodes. The vessel caught fire before sinking and thus numerous hull timbers were found charred. Three main degrees of charring have been recorded that presented major chemical differences which indicated different conservation requirements. This study investigated the correlation between the chemistry of the waterlogged timbers and their physico-mechanical properties, to assist in the development of an appropriate conservation strategy. Scanning electron microscopy documented the morphology of charred, semi-charred and uncharred samples. Moisture content and density were measured gravimetrically, while porosity was evaluated using mercury intrusion porosimetry. Hardness was assessed using a modified Janka test and a penetrometer. The results obtained showed that differences in chemistry were highly correlated to the physico-mechanical properties of the timbers. The charred wood presented the lowest moisture content, shrinkage and porosity among the three charring conditions and it also had the highest density, Janka hardness and resistance to penetration. The exact reverse properties were recorded for the uncharred material, which was typical of badly preserved, waterlogged wood. The semi-charred wood presented transitional features. These results indicate that the uncharred wood is in need of consolidation, in contrast to the charred and semi-charred material, which may be left to air-dry untreated.

INFLUENCE OF ANATOMY ON THE MECHANICAL RESISTANCE OF WOODS IN AN AGROFORESTRY SYSTEM

This study aimed to evaluate the influence of anatomy on the mechanical resistance of Parapiptadenia rigida (Benth.) Brenan, Peltophorum dubium (Spreng.) Taub., Eucalyptus grandis × Eucalyptus urophylla, and Schizolobium parahyba (Vell.) Blake from an agroforestry system. For this purpose, twelve 9-year-old trees were felled. To evaluate the anatomical properties, the specimens were taken from the diameter region at breast height (DBH at 1.30 m from the ground). To determine the mechanical characteristics, central planks from the DBH of the tree logs were removed to produce test specimens with dimensions of 2.5 × 2.5 × 41.0 cm. The modulus of elasticity, modulus of rupture, tension of the proportional limit, and maximum force were then evaluated. Conversely, test specimens with dimensions of 5 × 5 × 15 cm for were used for the transversal and longitudinal Janka hardness and perpendicular compression tests. The higher the cell wall fraction, vessel frequency, and ray frequency values, the better the mechanical properties. Conversely, with the increase in the fiber diameter, lumen diameter, vessel diameter, height, and width of rays, the values of the mechanical properties of wood are lower.

Janka Hardness Evaluation of Plantation-Grown Eucalyptus nitens for Engineered Flooring Applications

Hardness is commonly used to determine the suitability of a timber species for flooring applications. In this study, Janka hardness test is conducted on sawlog managed Eucalyptus nitens and regrowth forest Eucalyptus obliqua sourced from Tasmania, Australia. Plantation E. nitens timber is currently entering the Australian market and the feasibility of using this fast grown species in value added applications such as timber flooring is advantageous. Further to testing Janka hardness on solid timber samples, a regime of engineered timber flooring prototypes consisting of plantation E. nitens top layers, veneers and solid densified E. nitens boards were developed and subjected to Janka hardness test. The results were compared against solid E. obliqua flooring and a commercially available engineered flooring product with Tasmanian Oak top layer. The results showed that Janka hardness of plantation grown E. nitens, and E. obliqua currently available in the market are lower than the values published in the literature. This indicates that the material properties of fast grown plantation timber and regrowth forest material are different to the native forest timber properties published decades earlier. Furthermore, some of the tested engineered flooring prototypes showed similar behaviour to timber flooring products currently in market, suggesting that E. nitens engineered flooring would be suitable for domestic/light commercial flooring applications despite the general conception of unsuitability due to lower densities.

Janka hardness of hardwood species evaluated by the nondestructive sclerometric method

Janka hardness of hardwood species evaluated by the nondestructive sclerometric method

Effect of wetting and fungal degradation on performance of nailed timber connections

The effects of wetting and exposure to two decay fungi were evaluated on nailed slash pine sapwood timber assemblies. Sterilization had no significant effect on connection properties, but exposure to a brown (Fomitopsis ostreiformis) or a white rot fungus (Pycnoporus coccineus) was associated with 40–60 % losses in ultimate strength over 34 weeks. Attempts to more closely assess changes in wood around the fasteners using localized Janka hardness or longitudinal compression were confounded by density differences between earlywood and latewood. The results highlight the effects of decay on connector behaviour and suggest the need for more precise methods for characterizing the environment around the fastener.

Influences of hardening agent on some physical and mechanical properties of medium-density fiberboard

Effects of Ammonium chloride (NH4CI) as a hardening agent on thickness swelling (TS), water absorption (WA), screw holding resistance (SHR), Janka hardness, modulus of rupture (MOR), modulus of elasticity (MOE), and internal bonding (IB) properties of medium-density fiberboard (MDF) were evaluated. Target densities were 712 and 715 kg/m³ for hardener applied (0.75 kg/m³ solid as 10% solution (fiber dry wt.)) and unmodified factory made 18 mm thick MDF, respectively. A total of 400 samples were tested. Boards produced without hardener presented better mechanical properties except for SHR. Indeed, SHR was around 9.2% improved by hardener utilization. However, hardener utilization caused around 8.4%, 7.3%, 3.6%, and 1.3% decreases for MOE, MOR, IB, and Janka hardness, respectively. Surprisingly, soaking time caused opposite results for TS and WA. The TS and WA of the hardener utilized MDF decreased around 40.3% and 29.6% for short-term soaking (2h) but remarkable increases (around 62.4% and 20%, respectively) were observed for long-term (24h) soaking. Statistical analysis proved that there were statistically significant (P<0.05) differences between all the evaluated properties.

Use of Carbon and Basalt Fibers with Adhesives to Improve Physical and Mechanical Properties of Plywood

Currently, wood is presented as an alternative to traditional building materials and to mitigate climate change. Chile is one of the eight largest wood producers in the world; therefore, wood-based products are an easily accessible resource. The aim of this research is to reinforce at laboratory scale plywood panels with basalt and carbon engineer fibers using epoxy resin and polyvinyl acetate as an adhesive system to improve their physical and mechanical properties. Three-point static bending and Janka hardness tests were carried out. The results showed a better performance in the reinforced boards, which showed an increase in Modulus of Elasticity (MOE) and Modulus of Rupture (MOR) properties in the parallel direction of about 48.2% and 52.8%, respectively. Additionally, for the perpendicular direction, there was an increase of 52.0% and 102.9%, respectively. On the other hand, the Fiber Reinforced Polymer (FRP) plywood panels showed an increase of at least 37% on the Janka hardness property, obtaining higher results with the polyvinyl acetate (PVA) adhesive. Finally, FRP–plywood, PVA–BF and PVA–CF may be a new option for composite wood materials, with their ductile behavior and superior mechanical properties, especially in the perpendicular direction, where the increases were greater than those shown in unreinforced plywood.

Shear strength and hardness of two tropical wood species as function of heat treatment

The aim of this study was to evaluate the effect of heat treatment on surface roughness, shear strength and hardness of two tropical wood species, namely batai (Paraserainthes falcataria) and sesendok (Endospermum malaccensis). Samples were exposed to temperature levels of 120 ºC and 180 ºC for 3 h and 6 h. The surface quality of the control and heat-treated samples were determined using a stylus technique. Hardness and shear strength of the samples were evaluated using Janka hardness and block-shear test, respectively. The results reveal that the surface roughness of batai improved 3 % for 80-grit and 5 % for 180-grit samples while surface roughness of sesendok improved 7 % and 10 % for 80-grit and 180-grit, respectively by the increase of the heat temperature and prolonged durations. Analysis of variance (ANOVA) also revealed that most of the tested properties on the treated wood were significantly affected by the species, girt number and also temperature. In contrast to the untreated wood species, the heat-treated wood species exhibited lower values of shear strength and hardness. Overall, the hardness and shear of both species were adversely influenced by heat exposure.

English

The current study examines the physical and mechanical properties of branch wood from Holarrhena floribunda and Nesogordonia papaverifera, two of Ghana's least researched deciduous species. At an equilibrium moisture content of 12±2%, H. floribunda and N. papaverifera specimens had average density values of 467.53 and 720.80 kgm-3, respectively. The overall tangential and radial shrinkage was 3.8 and 3.2%, respectively, while the radial shrinkage was 2.8 and 1.8%. For H. floribunda and N. papaverifera, the modulus of rupture was 80.2 and 122.3 N/mm2, respectively, whereas the static modulus of elasticity was 8213.8 and 12902.8 N/mm2. Shear strength parallel to grain was around 11.9 and 16.5 N/mm2, whereas compression strength parallel to grain was approximately 36.6 and 52.3 N/mm2. H. floribunda and N. papaverifera have Janka hardness values of 6.2 and 10.3 N/mm2 tangentially, and 4.3 and 8.9 N/mm2 radially, respectively. The qualities of the branch wood of H. floribunda and N. papaverifera were equivalent to those of their stem wood and other known wood species, indicating that they might be used in a variety of wood-related applications.   Key words: Branchwood, Holarrhena floribunda, Nesogordonia papaverifera, Ghana.

Wear Resistance and Hardness Assessment of Five US Hardwoods for Bridge Decking and Truck Flooring*

Abstract The wear resistance and Janka hardness of five United States hardwood species were evaluated for potential use in bridge decking and truck flooring. The species tested include ash (Fraxinus sp.), hickory (Carya sp.), red oak (Quercus sp.), sweetgum (Liquidambar styraciflua), and white oak (Quercus sp.). The specimens were prepared with the sizes of 1 by 2 by 4 inches (2.54 by 5.08 by 10.16cm) for abrasion test and 1 by 2 by 6 inches (2.54 by 5.08 by 15.24 cm) for Janka hardness testing. The specimens were cut from 30 individual parent boards of random width with clear sections for each species. The abrasion and Janka hardness tests were performed according to the American Society of Testing and Materials standards. All wear and hardness data were statistically analyzed by 1-way analysis of variance. The results of this study demonstrated that sweetgum with the lowest density had the greatest amount of thicknesses loss and thus lowest wear resistance. White oak was found to have the least thicknesses loss, thus highest wear resistance among the hardwood species tested. Hickory, with the highest density, had the highest hardness among the hardwood species tested, but it had relatively lower wear resistance comparing to ash, red oak, and white oak.