جستجوی مقالات مرتبط با کلیدواژه « مقاومت های مکانیکی » در نشریات گروه « صنایع چوب و کاغذ »

The use of engineered wood products in the construction industry is constantly increasing due to various technical and economic reasons such as high strength-to-weight ratio, lack of restrictions in access to different dimensions, and the possibility of production using waste. I-shaped beams are one of the types of engineered wood products which Their properties can be controlled according to the design and the type of materials used in it.This study is done For the purpose of investigate the Reinforcement of I-shaped beams made with parallel strand lumber and laminated veneer lumber reinforced with glass fibers and epoxy resin. The variable factors of this research included the type of web and flange. The mechanical properties of the manufactured beams, including bending strength, modulus of elasticity, shear strength of the web, compressive strength parallel to the flange and compressive strength propertional limit of the flange were investigated and tested. The obtained results were analyzed in the form of a completely random design and Duncan's test was used to group the means. The results showed that the use of laminated lumber reinforced with glass fiber polymer in the web of beam compared with conventional laminated lumber Cause of improvement the modulus of rupture by 49.6%, the modulus of elasticity by 73.17%, the shear strength of the web by 55.55%, compressive strength parallel to the flange by 16/41% and 20.65% of the compressive strength propertional limit of the flange. Also, the use of laminated lumber reinforced with glass fiber polymer in the flanges of beams had a much better mechanical performance than conventional laminated lumber, parallel strand lumber and parallel strand lumber reinforced with glass fiber polymer.

Foams made from poly-lactic acid, which is a natural polymer, have been introduced as an alternative to petroleum-based foams. However, the use of these foams faces limitations in terms of physical and mechanical characteristics. To improve the quality of poly-lactic acid foams, natural nucleating agents such as cellulose derivatives can be used. The effect of micro-crystalline cellulose as a nucleating agent in the production of poly-lactic acid/wood flour foam with azodicarbonamide foaming agent was investigated. The results revealed that by increasing the foaming agent content up to 3% and the nucleating agent content up to 4%, the density of the foam panels decreased by 45.52%. The reduction in density was accompanied by an increase in porosity, expansion rate, water absorption, and thickness swelling throughout all treatment levels (1 to 3% foaming agent and 1 to 4% nucleating agent), and this decrease in density led to a reduction in tensile and flexural strength and an increase in impact resistance. The morphological changes of the produced foams were also confirmed by scanning electron microscopy (SEM) images.

This research investigates the cooking of monoethanolamine with a concentration of 50% and baking alkali sulphite with 18% alkalinity for making pulp from corn stalks. The combination of sodium hydroxide and sodium sulphite in rations of 70:30 as a measure of alkali sulphite and water and monoethanolamine with a ratio of 50:50 were selected as control treatments. The amount of deficiency was eliminated during all three processes due to the fact that it was not very minor and could not be weighed. Furthermore, the cooking conditions were chosen as variables: the process of alkali and soda sulphite was combined; time was 30:60:90 minutes at the three levels and the temperature was 125.145.165 degrees at the three levels; and the ratio of the baking fluid to the raw material (1 to 4) remained constant. The paper pulp produced with monovalent and 50% had the lowest amount of total efficiency (36.12) and kappa number (17.93). In alkaline sulphite treatment, it was observed that decreasing the temperature and increasing the time as variable factors, results in a decrease in the total return value and the kappa number likewise increases, so that the highest burst index (6.78) is related to baking with a temperature of 125 degrees and the total time would be 60 minutes.
The results of this study show that monoethanolamine/water (50:50) can be successfully used to make paper from corn stalks, and the characteristics of the pulp of manufactured paper, especially in terms of mechanical strength and kappa number, when mixed with water; and that it is superior to the process of alkali sulphite both as a combination and by itself

In this research, rice straw was used as raw material. Potassium hydroxide was combined with monoethanolamine (MEA) as liquor. In another processes NaOH/Na2So3, KOH/K2So3 and KOH 14% was used as references pulp. The results showed that using pure MEA(15%) produced the highest yield and the highest kappa number. By using potassium hydroxide as a additive agent in MEA pulping, the amount of reject, yield and kappa number was decreased and the lowest yield and the lowest kappa number relevant to MEA(15%) combined with KOH (40%). In addition, in KOH pulping observed that, with increasing concentration of MEA, as additive agent, the amount of total yield increased but the kappa number and reject content was decreased. Results showed that the highest tensile index and tear index were relevant to MEA (15%) combined with KOH (20%) and the highest burs index relevant to NaOH/Na2SO3 treatment. According to the optical properties, it was found that the highest brightness was achieved in K2SO3/KOH. The highest opacity relevant to the KOH14%. The result shows that MEA process in combined with Potassium hydroxide can be done success fully on rice straw and properties of pulp production, specially in aspect of mechanical strength, in term of combination is superior than soda and Potassium hydroxide process.

Increasing demand for light and durable materials in home and office furniture requires optimizing the properties of the products used. In this research the effect of skin type and core on mechanical properties of light weight sandwich panel was investigated. The skins were made of MDF with 3, 6 and 8 mm thickness, particle board with 8 mm thickness, three layer plywood with 3.8 mm thickness and five layers plywood with 7.28mm thickness. The cores of polyurethane foam and honeycomb of kraft paper (3 cm thickness) were used. Mechanical tests including bending strength, modulus of elasticity; impact bending and compression were performed according to DIN and ASTM standards. Result showed that, light sandwich panels made from polyurethane foam core had higher mechanical properties than the light panel made of kraft honeycomb core which indicates that the dense and homogenous structure and better linkage with skin. By increasing the thickness of skin in the samples made from MDF skin, the properties of sandwich panel increased. The best result of mechanical properties was observed in light weight sandwich panel made of plywood skin and polyurethane core.

Effect of Kraft lignin as a compatibilizer on the short-term water absorption (2 and 24 hours) and mechanical properties of wood flour-polypropylene composites was studied. The black liquor of Chooka pulp and paper mill was acidified and Kraft lignin was extracted by precipitation. The extracted lignin at three levels of 2, 5 and 10 percent was mixed with wood flour by physical mixing method. All materials used were oven-dried. Wood flour, lignin and PP with or without MAPP were used to produce composites by flat hot press method. The results of this study indicated that generally lignin improved physical (short term water absorption) and mechanical properties (flexural modulus, flexural strength and impact strength). The bending test result showed that without MAPP, the composites with 2 and 10 percent lignin exhibited higher flexural modulus and strength, respectively. But at the presence of compatibilizer, the composites with 5 percent lignin exhibited the highest flexural modulus and strength. The composite with 2 percent of lignin exhibited higher flexural modulus and short-term water absorption rather than the composites with 2% MAPP. This result indicated positive effect of lignin in the composites. Also the composites with 10 percent lignin exhibited the highest impact strength and short-term water absorption. But there were no significant difference between the impact strength of composites with 5 and 10 percent lignin.

This study was carried out to optimize of cationic starch use for improvement of the mechanical properties of mixed OCC & NSSC pulps. NSSC pulps were mixed with the OCC pulps by following weight ratios: 80/20، 70/30 and 60/40، respectively. Cationic starch was used in different charges of 0. 5، 1. 25، 2 and 3 %. The produced paper strength properties were measured according to Tappi standard. The results obtained from normalized equation showed that treatment of C4 (60% NSSC+ 40% OCC using 3% Cationic starch) is the best suitable samples. Also، by increasing the OCC proportion in mixed pulps، tensile، Tear، burst strengths increases، but Concora medium test (CMT) and Ring crush test (RCT) decreased. In general، by increasing of the cationic starch dosage، mechanical strengths has increased and its improved use had determined by 3% cationic starch.

In this study the possibility of bagasse fiber usage in Fiber-Cement Composite (FCC) manufacturing, was investigated. Two load of bagasse fiber (%4, 10), three level of calcium chloride as facilitator (5, 7.5 and 10 percent per dry weight of cement) and two type of Portland cement (type II and V) were considered as variables (12 treatments). There were three replicates for each treatment, thus 36 experimental board were manufactured totally. The physical and mechanical properties of experimental specimens were investigated and results analyzed by SPSS software as fully randomized factorial model. As results indicated, there was no significant different between cement type II and V in physical and mechanical properties. The increased loads of calcium chloride caused a striking reduction in mechanical properties and increased water absorption amounts. The best bending strength, modulus of elasticity, IB and minimum thickness swelling were reported in treatment with 4% fibers, 7.5% calcium chloride and type II cement.