مقاومت خمشی

In this study, the possibility of making a composite from bagasse was investigated. Bagasse-polypropylene fiber samples with different bagasse percentages (15, 25, and 35%) and coupling agent (0, 1.5, and 3%) were made, and their mechanical properties were examined. The results showed that with an increase in bagasse fibers, the flexural strength and tensile modulus did not change significantly, but the modulus of elasticity and energy at the breaking point decreased significantly, but the tensile strength increased. The results of the impact resistance test showed that although the impact resistance decreased and increased slightly with an increase in the percentage of bagasse fibers and coupling agent, this amount of decrease and increase was very small and insignificant, and the results of this test were random and unrelated to the increase in raw materials. However, in the impact resistance test without a notch, a significant difference in the decrease in impact resistance was observed with an increase in fibers and its increase with an increase in coupling agent. Overall, all measured engineering properties in this study improved, except for impact resistance, which decreased with an increase in fibers. It is suggested that to improve the engineering properties of this type of composite, the bagasse percentage and coupling agent should be increased up to 30% and 3%, respectively.

The purpose of this research is to investigate the possibility of producing hybrid particleboard from industrial wood chips with waste from vine pruning as a waste material that has no specific use and is thrown away. For this purpose, the particles from grapevine pruning residue and industrial wood chips were mixed with different ratios of 0:100, 30:70 and 40:60. Also, for making boards, two different levels of urea-formaldehyde resin were used, including 10 and 12% (based on the dry weight of wood chips) and the pressing time was 5 minutes. The physical and mechanical properties of the boards including thickness swelling (TS), bending strength (MOR), modulus of elasticity (MOE) and internal bonding (IB) were measured and then all the data were analyzed statistically. The results of this research showed that although the increase of particles from grapevine pruning waste led to a decrease in the characteristics of particleboards, but all the boards meet the European standard. On the other hand, increasing the resin content moderates the negative effect of these particles on the characteristics of the board and had a positive effect on all the characteristics of the boards. Therefore, by comparing the properties of the boards produced with the European standard (EN), it was determined that by using 30% of grapevine pruning wastes replaced with wood chips, it is possible to produce particleboard with desirable properties. The general results of this study show a positive result in the direction of using the wastes from pruning grape trees as a type of garden waste that is rejected after pruning and can also replace part of wood material in the construction of industrial panels and also it will be an income for gardeners.

In this study , Effect of nano cellulose Fiber gel bacteria as reinforcer on physical, mechanical and morphological properties of composites made of bagasse and cement has been studied. Nano variable factors in three levels (0, 1 and 3 % by weight of cement), the mixing ratio of bagasse as lignocellulosic material with Portland cement, in three levels (90:10, 80:20, 70:30%) was equal to the dry weight of cement. The target density 1.1 g/cm3 and 5% calcium chloride for all treatments were considered as Fixed factors. The mechanical and physical properties of composites includes modulus of rupture, modulus of elasticity, internal bonding, thickness swelling after 2 h and 24 h immersion in water and density of boards were measured according to the standard DIN-EN-634. In this study, to investigate the morphological properties of composites and how to distribute Nano, microscopic images (SEM) were taken from the broken cross-section of the samples. The results showed that boards made with nano fiber cellulose had more modulus of rupture, modulus of elasticity and internal bonding. The results also showed that with increasing nano, density, dimensional stability of the boards and heat hydration of cement mortar increased. The results from microscopic imaging (SEM) showed that cellulose nanofiber can fill the pores of the composite and create a uniform structure, thus improved the strength of the boards.

In this study, bending performance of the WPC profiles of Asre Honar company were measured, then were predited by finite element method (FEM) with ANSYS software to decrease the cost and time of measurement. Therefore, the bending strength of small control specimens with a span length of 180 mm were firstly measured. Accordingly, their bending modulus of elasticity (MOE) and Poisson's ratio of 0.3 were used as input data for prediction. Therefore, four types of hollow and solid WPC profiles with span lengths of 180 and 450 mm were tested under three-point bending loading with a Hounsfield 0308 testing machine with a loading rate of 5 mm/min. Subsequently, their MOR and creep values were measured and compared with those predicted by the FEM. The results of the analysis of variance (ANOVA) Table showed that the main effect of profile types on MOR was statistically significant. Furthermore, the main and the interaction effects of the span lengths and profile types on MOE were statistically significant. The investigation of the main effects revealed that MOR and MOE decreased by 8.8% and increased by 17.7%, respectively by raising the span length from 180 to 450 mm, and also they altered by 33.1% and 24.2% with the change in profile types. In addition, the interaction effects showed that MOR and MOE values changed by 43.9% and 66.6%, respectively with the simultaneous change of the span lengths and profile types. The results indicated that the FEM predicted the MOR values with a mean absolute percentage error (MAPE) of less than 3.03% and their corresponding creep with a MAPE of less than 15.25%. According to the satisfied MAPE of FEM, it could be suggested as an efficient method for predicting the bending properties of these products.

In this study, the mechanical properties of kenaf cement composite were investigated using different amounts of kenaf particles (mixture of kenaf core and bark and kenaf core particles). Kenaf-cement composites were manufactured at different levels (10, 15 and 20%) of different kenaf particles. Also, Portland cement and calcium chloride (as cement accelerating additive) were used in this research. Calcium chloride and water were mixed well and then kenaf particles were added to the mixture. At next stage, cement was added to the prepared mixture and all component were mixed well. Prepared mixture was molded to the wooden mold and kenaf cement composites were produced. The results obtained from mechanical evaluation of kenaf-cement composites showed the highest bending strength in 10% kenaf bark-cement composites. Also results revealed that highest modulus of elasticity of 10% kenaf core-cement products were obtained. The results of this research revealed the potential of kenaf particles as reinforcement in cement composite production.

 In the current research, surface properties and failure modes of modified poplar wood (Populus deltoides) by hygrothermal treatment were evaluated. For this aim, the effect of variable factors included hygrothermal temperature (three levels: 130, 150 and 170°C) and holding time (two levels: 20 and 40 minutes) on poplar wood specimens properties (contact angle and surface roughness) prior to and after planning were investigated. The surface characteristics and failure modes were evaluated for both treated and untreated wood specimens. The results revealed that surface roughness of poplar wood was enhanced due to the hygrothermal treatment in both states of before and after planning. It was also found that the hygrothermal treatment decreased contact angle of distilled water. The bending strength of specimens was reduced by hygrothermal treatment. According to the results, failure modes of hygrothermally treated specimens were simple and compression types in bending strength test. Keywords: Surface roughness, contact angle, bending strength, failure mode

The aim of this study was to construct lightweight structures and reduce energy loss. The aim of this study was to produce cement wood or composite products by combining organic particles such as wood fibers and lignocellulosic materials with monolith. The investigated product consisted of cement wood made from scrap wood fibers and poplar wood particle thickness of 20 mm on both sides of the structure and 10 mm thick unolith in the middle of the structure. Products manufactured by Unolite Cement will have a combination of cement and Unolite properties. In this study, according to the studied variables including lignocellulosic materials and amount of additive (such as calcium chloride (Cacl) at two levels of 3 and 5%, the best specimens were prepared using 10% lignocellulosic materials. The thickness of the specimens was uniform at the two monolithic surfaces and all fabrication conditions such as discharge rate, press pressure, coalescence rate were assumed to be uniform and constant.In static bending experiment the mean maximum load force for ordinary brick failure was 3933.26N and the mean. The maximum load for breaking the cement stick was 389/78 N, which was approximately It has 10% resistance to ordinary brick but ordinary brick breaks abruptly when fractured, while the monolithic brick is gradually broken and the insulation properties due to the cellulosic fibers and the monolith in it are higher than the ordinary brick due to its low resistance to use. Recommended in partitions.

This study evaluated the effects of flange thickness to depth of web ratio at three levels (1:2, 1.5:3.5 and 2:5) as well as thickness to depth of web ratio at three levels (0.5:2, 0.5:3.5 and 0.5:5) and width of flange at three levels (3, 3.8 and 4.6 cm) as independent variables on some mechanical properties e.g. modulus of rupture (MOR) and modulus of elasticity (MOE) of I-joist manufactured from ash wood (Fraxinus sp.). For this purpose, response surface methodology (RSM) was applied to evaluate the effects of independent variables on MOR and MOE of I-joist based on a three-level, three-variable central composite rotatable design (CCRD). In this survey, bending test was done according to the ASTM D-5055. Mathematical model equations were derived from computer simulation programing to find significant differences and the most effective variables. According to the results, predicted values were found to be in agreement with actual values (R2 values of 0.99 and 0.98 for MOR and MOE, respectively). The study showed that RSM can efficiently be applied in modeling bending properties of I-joist. It was found that all independent variables had direct effect and significant effect on responces; in a way that flange thickness to depth of web ratio, thickness to depth of beam web ratio and width of flange maintained the MOR and MOE at maximum levels up to 2:5, 0.5:5 and 4.6cm, respectively. Simultaneously, some quadratic and interaction terms of variables had significant effects, too. Generally, increment in flange thickness to depth of web ratio, thickness to depth of web ratio and width of flange increased MOR and MOE of I-joist. Besides, flange thickness to depth of web ratio had the strongest effect on bending strength of beams

The aim of this investigation was concentrated on the possibilty of untilizing corn cops residues in the production of particleboard. Two press temperatures of 170 and 180 oC, and four ratios of corn cop/poplar wood particles (100/0, 75/25, 50/50 and 25/75) in the corn layer of the boards and 100% poplar wood particles in the surface layer were used. A combination of 16 treatments were reached and three laboratory boards for each treatment were made. Physical and mechanical properties of the boards were measured and statistically analyzed. The grouping of the averages were based on duncan multiple range test. The results indicated that the influence of the press temperature on both modulus of rupture and modulus of elasticity was statistically significante and boards produced applying 170 oC reached higher values. As the ratio of the corn cop particles in the particle mixture in core layer increased, both modulus of rupture and internal bonding deteriorated and the highest value were measured at 50/50 ratio of the particle in the core layer. The Boards which produced applying higher press temperature exhibited hgiher rate of thickness swelling . Lower ratios of the corn cop particle in the mixture of particles in the core layer improved the properties of the boards. So that the ratio of 50/50/ and 25/75 produced lower thickness swelling. The results of this research revealed that eventhough boards produced using corn cop particles did not produce comparable properties to the boards based on poplar particles, but it can be concluded that if 50/50 ratio of particles, press temperature of 170 oC is used for board making, the mechanical properties of the produced boards will meet the requirement of DIN specifications.

In this study, modulus of rupture (MOR) and modulus of elasticity (MOE) of glued-laminated timber (Glulam) made out of poplar (Populus alba) with galvanized steel nail, brad strip nail, coarse thread drywall screw for applying pressure were investigated and compared with those constructed with cold press. Amount of polyurethane adhesive was 300 g/m2. Thickness, width and span of 3-ply glulam specimens were 57, 80 and 640 mm, respectively. Static bending test was performed according to ASTM D 7341 by Instron testing machine. The results showed that the higher MOR and MOE were related to Glulam connected by 4 screws on 8×8 cm2 with adhesive (69.3 MPa), and those connected by 2 galvanized steel nail with adhesive (6737.7 MPa), respectively. The results also revealed that the lower MOR and MOE were both observed in Glulam connected by 2 brad strip nail without any adhesive (23.9 and 1252.7 MPa, respectively). The results showed that MOR and MOE of glulam were changed with the independent variation of number of fastener 3.7 and ˂1%, respectively. The higher variation was related to independent effect of adhesive (130 and 317.8% for MOR and MOE, respectively). Analysis of variance indicated that only the independent effect of adhesive application was only statistically significant at 95% confidence level. The comparison of MOR and MOE of Glulam made with two fasteners with those constructed by cold press showed that there was not significant difference between them. So, the use of galvanized steel nail, brad strip nail, coarse thread drywall screw for applying pressure to manufacture Glulam instead of cold press is possible and the best item was brad strip nail due to easy application and installation by pneumatic nailer and low cost.

In this study, the composition of bagasse composite was investigated using different amounts of bagasse particles. Bagasse and cement particles are manufactured at levels (5, 10 and 15%) and percentage of calcium chloride as cement accelerating additive at two levels (3 and 2%) based on cement dry weight. Then, the mixture was poured into a mold measuring 15 8 18 8 8 cm and the excess water was removed from the bottom of the mold and initially weighed 10 kg on the specimens. The specimens were removed from the mold after 48 hours and kept in a glass saturated room at 90% humidity for 14 days and then finally dried in a laboratory environment. The bending strength and physical properties tests were performed on the specimens. The results showed that bagasse particles had a significant effect on bending strength and other physical properties. The bending strength was highest in boards made with 10% bagasse particles.

The large parts of the southern regions of Iran are covered by wild milkweed plants. The latex and roots of these plants are used in the pharmaceutical industries, but the wooden parts of this plant are left as waste. Since lots of this type of wastes are annually produced; hence, we conduted this study to use lignocellulosic wastes of wild milkweed plants for the manufacturing of wood-plastic composite and then the mechanical properties of the fabricated compositewere studied. To make composite, milkweed flour in three mixing levels of 30, 40 and 50 percent of total composition, maleic anhydride grafted polypropylene as a coupling agent in two mixing levels of 4 and 6% percent of polymer, were used as variable factors. Also, some of the wood was not debarked, and the level of 40%, was made using debarked wood flour.The mechanical properties of fabricated composite including bending strength, bending modulus, tensile strength, tensile modulus and impact strength, were measured.The study results showed that by increasing milkweed flour consumption, the tensile strength of composite was decreased, but the bending strength was improved. In each of the different mixing levels of milkweed flour (30, 40 and 50 percent), the flexural modulus and tensile modulus of composites increased by increasing the amount of coupling agent (from 4 to 6%).On the other hand, the impact resistance of composites decreased by increasing the amount of lignocellulosic flour in each of the coupling agent mixing levels. Also, the presence of the skin did not adversely affect the mechanical properties of the composite, and it is possible to use this type of wood without the need of debarking.

The purpose of this study was to investigate the possibility of using tobacco stalk and industrial wood particles in particleboard industry as a waste material that is not consumed and discarded and has a low price, followed by a reduction in production costs from the way of choosing this raw material was of low value. For this purpose, the particles of tobacco stalk and industrial wood particles with different ratios of 0:100, 30:70 and 60:40, using the amount of adhesive used 12% and 14% (based on the dry weight of the wood chips) and the press time of 5 minutes for the construction of the board was considered. Physical and mechanical properties including thickness swelling after 2 and 24 hours immersion in water and bending strength (MOR), modulus of elasticity (MOE) and internal bonding (IB) were measured and all data were statistically analyzed. According to the results of this study, the increase in tobacco stalk particles resulted in increased thickness swelling after 2 and 24 hours immersion in water and reduced bending strength, modulus of elasticity and internal bonding, but all boards had a European standard (EN). Increasing the amount of resin also had a significant effect on all the properties of the boards and improved the properties. In a general conclusion and by comparing the properties of the boards produced with the European standard (EN), showed that using 60% tobacco stalk and 12% urea formaldehyde resin can be produced particleboard with the desired properties. This is a positive result of using tobacco stalk as a type of agricultural residue and, consequently, the prevention of environmental pollution caused by the burning of these compounds.

The purpose of this study was to use of Hemp stalks in particleboard production. Mixtures of Hemp stalk and Eucalyptus wood at the ratios of 0:100, 50:50, 100:0 were used. Also two resin content of 8 and 10% (based on oven dry particle) and 2 press times of 3 and 4 minutes were employed for the production of laboratory particleboard. Physical and mechanical properties including thickness swelling after 2 and 24 hours soaking in water, modulus of rapture, modulus of elasticity and internal bonding were measured data were statistically analyzed. It was observed that the increase in Hemp stalk particles in the mixture resulted in increasing of bending properties (bending strength and modulus of elasticity) and thickness swelling after 2 and 24 hours water soaking. Also the results showed that increase in Hemp stalk particles in the mixture resulted in reduction of internal bonding. As expected, physical and mechanical properties of particleboard improved with increasing resin content. Modulus of elasticity and thickness swelling after 24 hours water soaking were improved with increasing of press time. In general, comparing the produced board mechanical properties with standard of Iran requirements, the board produced using 100% and 50% Hemp stalk, 8% resin content and 3 minutes press time showed that optimal properties. Although the physical properties of the boards did not meet the standard values, the reason for this could not be due to the lack of use of paraffin.

In this study, the pruning branches of mulberry trees mixed with industrial wood chips were used in the manufacture of particleboard. Then the physical and mechanical properties of the boards were investigated. For this purpose the study variables included the amount of mixing mulberry branches with industrial wood chips in four levels 0/100, 10/90, 20/80 and 30/70 and the amount of urea formaldehyde resin at two levels 12 and 14% of the dry weight of the wood chips. The results showed that increasing the amount of particles obtained from mulberry tree branches up to 20 %, had no negative impact on the physical and mechanical properties of the boards. Increasing the amount of these particles up to 30 percent had a negative impact on the physical and mechanical properties of the boards, but with increasing the amount of urea formaldehyde resin up to 14 %, could be improved dimensional stability, bending strength, modulus of elasticity and internal bonding of the particleboards.

This study was carried out to investigate the effect of storage time and moisture content of bagasse on the physical and mechanical properties of particleboard. For this purpose, wet depitting bagasse was used and samples were maintained in bailing storage method. In this study, was applied 4 storage times (1.5, 3, 4.5 and 6 months) and 2 moisture content of Bagasse (45% and 55%). According to these variables, particleboards were made. Also chemical properties (pH, acid and alkaline buffering capacity) of Bagasse were determined. The mechanical and physical properties of the boards were measured and statistically analyzed using factorial experiment and complete randomized design. Then Duncan multiple range test was used for grouping of the averages. The results revealed that with decreasing of Bagasse moisture content, Bagasse sample pH and acid buffering capacity were decreased and increased, respectively. Also bending properties and thickness swelling after 24 hours immersion of the boards were improved. With increasing of storage time, the chemical properties of Bagasse tend to be alkaline, and the minimum of board internal bond strength was obtained in 1.5 month storage time. The physical properties of boards were improved with increasing of storage time

In this research, the manufacture of particleboard using lignocellulosic residues including wheat straw and tobacco stalks mixed with industrial wood chips were studied. The variable factors included the mixture of wheat straw and tobacco stalks with industrial wood chips in four levels 0/100, 20/80, 40/60 and 60/40 (In any combination, according to the desired levels, tobacco stalks and wheat straw were used equally) and the amount of urea formaldehyde resin was at two levels 12 and 14% of the dry weight of the wood chips. The results showed that by increasing the mixture of wheat straw and tobacco stalk up to 60 percent, the physical and mechanical properties of the boards decreased significantly. But increasing the amount of adhesive consumption up to 14 percent had a positive impact on the physical and mechanical properties of the boards and improved internal bonding, bending strength and modulus of elasticity and dimensional stability of the boards. It means that by increasing the use of this type of wastes up to 40 percent with an increase in the amount of UF adhesive up to 14% can be produced the boards with the mechanical properties at standard level.

In this research، the combined effect of impregnation of wood with nanosilver solution and hygrothermal treatment on some physical and mechanical properties of beech (Fagus orientalis Lipskey) and spruce (Piceaabies) woods was studied. Wood specimens، Initially، were impregnated in an impregnation cylinder for 20 minutes at the pressure of 0. 25 MPa، with nanosilver solution. Then، hygrothermal treatment was carried out at the temperatures of 120، 150 and 180°C for 1، 3 and 5 hours. Control specimens، without any impregnation process، were hygrothermally treated. Volumetric Swelling after 2 and 24 hours soaking in water، bending strength، impact load resistance and compressive strength parallel to the grain of specimens were measured، according to ASTM D143 and all data were analyzed statistically. The results showed that swelling and mechanical properties were decreased by increasing the temperature and duration of hygrothermal treatment. Also، nanosilver impregnated specimens which were treated at 180 ˚C had lower swelling without Not clear and not seems. Consequently or it can be concluded that with nanosilver impregnation process of wood، hygrothermal treatment would be carried out at higher temperature (180 ˚C) to obtain better dimensional stability with no more decrease in mechanical properties.

The purpose of this study was to examine the physical and mechanical properties of particleboard made using corn stalk. Mixtures of corn stalks and industrial wood particles at the ratios of 0:100, 30:70, 50:50, 70:30, urea-melamine formaldehyde resin at two levels of 10 and 12% (based on the dry weight of the particles) and two press times of 5 and 6 minutes were used for the production of laboratory particleboard. Physical and mechanical properties including water absorption and thickness swelling after 24 hours soaking in water, modulus of rupture, modulus of elasticity and internal bonding were measured and the data were statistically analyzed. It was observed that the increase in corn stalk particles in the mixture resulted in reduction of water absorption, thickness swelling after 24- hours water soaking and the internal bonding. The modulus of rupture and elasticity of the boards were increased at higher ration of corn stalk particles. The higher dosage of resin and higher press time imposed significant effect on all properties boards and improving properties were reached. In general, comparing the produced boards properties with EN 312 requirements, the boards produced using 70% corn stalk particles, 12% urea-melamine formaldehyde and 6 minutes press time showed optimal properties.

The effect of nanoclay particles addition to composite mixture on mechanical properties of HDPE/ wheat straw powder was studied. The composite compound was prepared using 35% wheat straw as reinforcement, 63% high-density polyethylene (HDPE) and 2% MAPP as coupling agent and different amounts of nanoclay (1%, 2% and 3%) were used. The composite compound was made using a counter-rotating twin-screw extruder and test specimens prepared by injection molding. Results showed that at higher dosages of nanoclay particles, the flexural strength and tensile strength increased. However, the addition of nanoclay particles has led to the decreased impact strength.