Physics and Mechanical Wood
foroogh dastoorian; Mohammad Layeghi; Ghanbar Ebrahimi; Mehdi Tajvidi; Seid Majid Zabihzadeh
Abstract
In the present study, creep rupture behavior of a bagasse fiber- polypropylene composite was investigated. Two accumulated damage model (EDRM and Wood) and an energy based failure model (R-W) were adopted to describe the load duration influence on the studied composite. Results have shown that at very ...
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In the present study, creep rupture behavior of a bagasse fiber- polypropylene composite was investigated. Two accumulated damage model (EDRM and Wood) and an energy based failure model (R-W) were adopted to describe the load duration influence on the studied composite. Results have shown that at very high stress levels, the EDRM and Wood models underestimated and overestimated the time to failure than static value respectively. This was attributed to the difference between application of static loading and creep loading. Findings indicated that the all three models were able to describe the creep rupture behavior of the studied composite and among this; the Wood model has shown a better fitting with experimental data, statistically. Based on findings in the present research, it can be concluded that the R-W model was more conservative in predicting time to failure in comparison with the two other models, and the reason can be attributed to the difference between failure criteria in energy based models and accumulated damage models. Results also showed that with increasing stress levels, the secondary stage of creep will shorten and at high stress level, the tertiary stage of creep will be more dominant
asghar tarmian; Seaid Alireza Dehghan; Elnaz Trighnoor; Mohammad reza Pyramon; Razyeh Shamsy; Mohammad Layeghi
Abstract
In this research, the performance of a semi-greenhouse solar kiln was evaluated for dying different wood species in different season in Karaj. This study was carried out in two separate parts. In the first part, the flat-sawn boards of oak and fir with a nominal thickness of 50 mm were dried during summer ...
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In this research, the performance of a semi-greenhouse solar kiln was evaluated for dying different wood species in different season in Karaj. This study was carried out in two separate parts. In the first part, the flat-sawn boards of oak and fir with a nominal thickness of 50 mm were dried during summer of the year 2012. In the second part, the flat-sawn boards of beech and poplar with the same thickness were dried in autumn, 2014 and spring, 2015. For both parts, the boards were also air-dried. The temperature measured inside the solar kiln was 35 ºC greater than that outside during daytime and also the kiln temperature ranged from 55 to 75ºC during 10 a.m. to 2 p.m.. In both parts of research, all wood species dried in the solar kiln faster with better quality compared to those air-dried. The severity of casehardening and surface checking in the boards dried in the solar kiln was lower and more homogenous moisture profile was observed. In addition, the final moisture content was lower for the boards dried in the solar kiln.
Mechanical conversion of wood and wooden fittings
Hamideh Abdolzadeh; Ghanbar Ebrahimi; Mohammad Layeghi
Abstract
In this study, structural performance of corner joint reinforced by fiber reinforced polymers (FRP) at the area of maximum tension stress was investigated under diagonal tension loading. Therefore 1 to 3 layers of unidirectional woven Glass, Carbon and Kevlar fibers were used and hand ...
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In this study, structural performance of corner joint reinforced by fiber reinforced polymers (FRP) at the area of maximum tension stress was investigated under diagonal tension loading. Therefore 1 to 3 layers of unidirectional woven Glass, Carbon and Kevlar fibers were used and hand lay-up was done by vinyl ester and epoxy resins. Results of load-displacement curve at yield point exhibited capability of the reinforcing layers in preventing joint opening to some extent under load. However, failure was observed at the joint due to picking fibers from wood surface or members fracture near the interface when loading increased. Since the reinforced zones of the joints by FRP show the maximum shear stress, consequently the separation of fibers from wood surfaces increased at these locations. The adhesion of FRP layers to joint surface was not appropriate due to difficult process of layering at right angle of joints followed by probable formation of air bubbles. The results of assessing FRPs reinforcing behaviour indicated that application of vinyl ester in comparison with epoxy as matrix exhibited better performance. In addition, glass and carbon fibers showed better performance than Kevlar fibers as reinforcing agents.
Pulp and paper
farzaneh shiralizadeh; mohammad azadfallah; ali Abdolkhani; mohammad Layeghi; saeed mahdavi
Abstract
This study was conducted with the aim of producing laboratory samples of transparent paper using overbeating method. Hence, bagasse bleached soda pulp was subjected to post-bleaching sequence of DED to remove residual chromophores. Then this pulp was refined in a PFI mill to reach different ...
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This study was conducted with the aim of producing laboratory samples of transparent paper using overbeating method. Hence, bagasse bleached soda pulp was subjected to post-bleaching sequence of DED to remove residual chromophores. Then this pulp was refined in a PFI mill to reach different levels of 55, 130, 200, and 260 mL,CSF (Canadian standard freeness) freeness. Then handsheets were made according to TAPPI standard T 205 om– 8. Results indicated that refining has significant effect on optical properties especially transparency so that the maximum value was observed using pulp with the minimum freeness, i.e. 55 ml. The variations of transparency due to refining were also further explained by measuring scattering coefficient, opacity and brightness of the specimens. In addition, mercury porosimetry and analyzing the pictures of scanning electron microscopy (SEM) demonstrated the extensive variations of pore structure in paper during refining which impose great influence on developing transparency.
Mosayeb Dalvand; Ghanbar Ebrahimi; Mehdi Tajvidi; Mohammad Layeghi
Abstract
The bending moment resistance under diagonal tensile load of doweled joint in plywood members was investigated. Joint members were cut from 11-ply hardwood plywood (Beech, Hornbeam and Alder) at the nominal thickness of19 mm. Dowels were made of Beech and Hornbeam woods. Dowel diameters (6, 8 and10 mm) ...
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The bending moment resistance under diagonal tensile load of doweled joint in plywood members was investigated. Joint members were cut from 11-ply hardwood plywood (Beech, Hornbeam and Alder) at the nominal thickness of19 mm. Dowels were made of Beech and Hornbeam woods. Dowel diameters (6, 8 and10 mm) and depths of penetration (9, 13 and17 mm) in the joint members were selected as variables. The effect of dowel variables on the bending moment of the corner joints was evaluated. Results showed that the dowel diameter, penetration depth and species exerted a significant effect on the bending moment resistance under diagonal tensile load. Bending moment resistance under diagonal tensile load was increased as the diameter of the dowel increased from 6 to8 mmand as the penetration depth of dowel increase from 9 to13 mm. However, increasing the diameter from 8 to10 mmor the penetration depth from 13 to17 mmhad no significant effect on bending moment resistance under diagonal tensile load. Results also indicated that bending moment resistance of joints made with beech wood dowels provided higher resistance than hornbeam dowels.
Sadegh Maleki; Mohammad Mehdei Faezipour; Ghanbar Ebrahimi; mohammad Layeghi
Abstract
The goal of this study was to investigate bending moment resistance of L-shaped screwed corner joints constructed of Plywood members. The thickness of plywood members was nominal 19mm that were compared with medium density fiberboard (MDF) and particleboard with 18mm thicknesses. Effects of thread screws ...
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The goal of this study was to investigate bending moment resistance of L-shaped screwed corner joints constructed of Plywood members. The thickness of plywood members was nominal 19mm that were compared with medium density fiberboard (MDF) and particleboard with 18mm thicknesses. Effects of thread screws (coarse and fine), screw diameter (3.5, 4 and 5 mm), and penetration depth (9, 15 and 28) on bending moment capacity of joints under diagonal tension were investigated. Test results indicated that a screw corner joint becomes stronger as either screw diameter or screw length is increased. Screw length was found to have a greater effect on moment capacity than the diameter. The highest bending moment resistance was observed for joints made with coarse screw which were 5 mm in diameter and 28 mm depth of penetration. The lowest bending moment resistance was observed in joints having fine screw, with 3.5 mm diameter and 9 mm penetrations. Results also showed that bending moment resistance with coarse thread drywall screws was higher than those of the fine thread drywall screws. Bending moment resistance of joints made of plywood was higher than those of joints made of medium density fiberboard (MDF) and particleboard.
Akbar Rostampoor haftkhani; Ghanbar Ebrahimi; Mohammad Arabi; Mehdi Tajvidi; Mohammad Layeghi
Abstract
The purpose of this study was to investigate the effects of the screw diameter and pilot holes diameter as well as end distance, thickness of side and main members and screw type on the lateral load of joints made from various screws on commercial wood-plastic composites. Three types of screws, including ...
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The purpose of this study was to investigate the effects of the screw diameter and pilot holes diameter as well as end distance, thickness of side and main members and screw type on the lateral load of joints made from various screws on commercial wood-plastic composites. Three types of screws, including sheet metal screws with gauges 8, 10, 14 (4, 5, 6 mm, nominally), wood screws with gauge 8 (4mm, nominally), and drywall screws with gauge 8 (4mm, nominally) were used. The results showed that lateral load of joints do not increase continuously with increase of screws diameter and this must be attributed to decrease of net section of joint members. However, with a given diameter of screw, lateral load of joint increased with the increase of end distance, thickness of joint members. Also, results showed that, with the increase of predrilled holes diameter up to root-diameter of screw, lateral load of joint decreased drastically. Concerning screw type effect, the lateral load of joint made using wood screw was higher than joints made with sheet metal and drywall screws.
Composite wood products
Mohammad Arabi; Mohammad mehdi Faezipoor; Mohammad Layeghi; Ali akbar Enayati
Abstract
The purpose of this study was to investigate which equation (Linear, Exponential equation and quadratic) can describe exactly the interaction effect of particle size and adhesive percent and predict mechanical properties of particleboard (modulus of rupture, modulus of elasticity and bending strength). ...
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The purpose of this study was to investigate which equation (Linear, Exponential equation and quadratic) can describe exactly the interaction effect of particle size and adhesive percent and predict mechanical properties of particleboard (modulus of rupture, modulus of elasticity and bending strength). For this work three levels of density including 0.65, 0.7, and 0.75 g/cm3 and also, three levels of adhesive content including 8, 9.5, and 11% and four levels of slenderness ratio of particles including 46.35, 33.7, 21.51 and 12.87 were used. After conducting the experiment and preparing the data, three kind of equation (linear, quadratic and Exponential equation) for each mechanical property based on slenderness of particles, density and adhesive percent obtained. The result indicated there was no correlation between mechanical properties of particleboard and quadratic equation but there were good correlations between linear and Exponential equation. Also the result indicated that Exponential equation can describe efficiently the simultaneous effect of slenderness and adhesive present on the mechanical properties of particleboard, and it can predict better mechanical properties than linear equation.
