Dynamic and static elastic properties beech wood joints were assessed. Conventional joints, namely dovetail, tongue and groove, dowel, and halving joints were prepared with beech wood (Fagus ...orientalis Lipsky) using polyvinyl acetate and cyanoacrylate adhesives. The results of the dynamic and static modulus of elasticity of the joints in this research indicated the highest reduction trends in halving, dowel, tongue and groove, and dovetail joints, respectively. The modulus of dovetail joint elasticity, its homogeneous joint texture, and lack of an extended adhesive line, corresponded to that of the jointed samples. The average static modulus of elasticity was approximately 10.5% lower than that of the dynamic modulus of elasticity. The results of the Student’s t-test indicated a significant difference between the mean of dynamic and the mean of static modulus of elasticity, significance at 5% level and the Pearson correlation test indicated that the dynamic and static modulus of elasticity of the samples were significant at the 5% level and indicated a positive correlation. Based on the observed correlation in the dynamic and static tests’ results, using these methods, dynamic assessment of NDTs may be regarded as an appropriate alternative in standardizing destructive static testing for wood assessment and categorization.
The objective of this research was to study the feasibility of producing biodegradable thermoplastic starch rice-husk composites. The effect of different types of mineral fillers on the various ...properties of thermoplastic starch composites filled with rice-husk flour, an agricultural waste residue, was studied. The mineral fillers aluminum trihydrate (ATH), magnesium dihydroxide (MDH), nanoparticulate MDH, and nanoclay were studied. It was found that the addition of the mineral fillers and especially nanofillers improved the dimensional stability and the mechanical properties of the composites, while decreasing their biodegradability. The thermogravimetric analysis (TGA) showed that substituting mineral fillers for some part of the lignocellulosic component increased the extents of weight-loss in the first and second steps, but decreased the weight-loss in the last step. This substitution also led to a slight decrease in the thermal decomposition temperatures at the curve peaks.
Effects of adding small amounts of cellulose nanofibers and nanoclay particles on physical and morphological properties of biodegradable composites made of starch thermoplastic polymer and industrial ...sawdust were investigated. For this purpose, these nanoparticles were mixed with wood plastic composites (WPCs) at 0%, 3%, and 5% weight percent. Water absorption, thickness swelling, thermal dynamic mechanical tests, and also degradation tests were performed according to corresponding standard test methods. The results showed that adding small amounts of cellulose nanofibers and nanoclay particles can be successfully used as filler and improve overall performance of the above-mentioned WPCs.
The effects of the amount of nanographene on physical, mechanical, and thermal properties and morphology of the wood-plastic composites were investigated. This wood-plastic was made using recycled ...high density polyethylene (HDPE), nanographene, and wood flour. Four weight levels, 0, 0.5, 1.5, or 2.5 wt.% of nanographene, were combined with 70% polymeric matrix and 30% lignocellulosic material with an internal mixer. The results showed that by increasing the amount of nanographene up to 0.5% by weight, the flexural strength, flexural modulus, and notched impact strength of the composite increased. After adding 2.5 wt.% nanographene, these properties were reduced. By increasing the amount of nanographene, both the amount of residual ash and the thermal stability increased. Study of the images from scanning electron microscope (SEM) showed that the samples containing 0.5% of nanographene had less pores and were smoother than other samples.
The effects of steamed Populus deltoides fiber were studied relative to the physical, mechanical, and morphological characteristics of composites made from virgin polypropylene. Fibers of Populus ...deltoides were used during the reinforcement phase at 180 °C for 1 h. The tests were carried out with 57% of virgin polypropylene that was combined with 3% of maleic anhydride-modified polypropylene and 40% of wood fiber. The wood fiber portion consisted of either non-steamed fiber, steamed fiber, and an equal mixture of the two kinds of fiber. Mixing was done using an internal mixer at 180 °C and 60 rpm, and the standard samples were constructed by injection molding. Then, the physical and mechanical characteristics of samples were measured. To consider compatibility between the matrix and reinforcement phase, SEM pictures were taken from the break surface of composite samples. The results showed that the composites’ strengths were affected by steam, as components having steamed fibers had the best mechanical strength and dimensional stability, and also the least water absorption and thickness swelling.
The effect of nanographene amount was evaluated relative to the physical, mechanical, thermal, and morphological features of wood-plastic composites. Composites were prepared using recycled ...polyethylene (high-density polyethylene), nanographene, and wood-flour. The amount of 80% of polymer matrix and 20% of wood flour, and nanographene at four weight levels of 0.5%, 1.5%, and 2.5%, were used. An internal mixture was utilized for making the samples. The results showed that with the 0.5 wt% increase of the amount of nanographene, the tensile and flexural strengths, the flexural and tensile modulus and the notched impact strength composite increased. With the addition of 2.5 wt% nanographene, these properties decreased. With the increase of the level of nanographene by 2.5 wt%, water absorption and the thickness swelling of the composite decreased. With the increase of the level of nanographene, the level of residue ash and thermal stability also increased. Scanning electron microscope images showed that the samples with 0.5 wt% nanographene had less holes and a smoother surface compared to the other samples.
The aim of the research was to study the potential of lignocellulosic fillers such as flour of rice hull, wood saw dust, sanding flour from Medium Density Fiberboard (MDF), and sawdust from ...particleboard as reinforcement for recycled high density polyethylene. Natural filler HDPE composites were made from recycled HDPE and lignocellulosic fillers at 60% by weight filler loadings using a dry blend/hot press method. In all compounds 3 per hundred compound (phc) Maleic Anhydride Polyethylene (MAPE) was used. Nominal density and dimensions of the panels were 1g/cm3 and 35×35×1 cm. Physical properties of panels including short and long-term of water absorption and thickness swelling and mechanical properties, including flexural modulus, flexural strength, strain at yield, and energy to yield point were studied. Composites containing sanding flour from MDF showed higher short-term values of water absorption and thickness swelling. For the long term, such as maximum values of water absorption and thickness swelling and diffusion coefficient, composites including wood sawdust showed higher values, and composites contain rice hulls exhibited the lowest values. In addition, composites made from sanding flour from MDF showed high value of the swelling rate parameter. Water absorption behavior of studied composites followed Fick’s model. The flexural properties of composites were investigated with reference to the effect of filler type. Composites containing sanding flour from MDF and particleboard sawdust exhibited better flexural properties than others and composites containing wood sawdust showed the lowest values.
This study examined the effect of altitude on bending creep behavior of hornbeam lumber (Carpinus betulus). For this purpose, 9 hornbeam trees from three different altitudes (400, 800 and 1100 m) in ...the northern forests of Iran were selected. Clear samples were cut from mature wood in diameter at breast height (DBH). 108 prepared samples (dimensions: 2.5 × 2.5 × 41 cm) were conditioned at room temperature of 20 ºC and two relative humidities (RH) of 65 % and 95 %. First, the maximum bending load was determined by three-point static bending tests in acclimatized room and then flexural creep parameters, such as relative creep, creep modulus and creep factor, at 20 % of the maximum bending load, were calculated. Results indicated that at 65 % RH, the effect of altitude on creep parameters was significant. The maximum values of relative creep and creep factor were observed at the altitude of 800 m, and the minimum values at the altitude of 400 m. The maximum values of creep modulus were observed at the altitude of 400 m and the minimum values at the altitude of 800 m. Also, at 95 % RH, the effect of altitude on creep modulus was significant but it was not significant on relative creep and creep factor. The maximum creep modulus was observed at the altitude of 400 and the minimum at the altitude of 800 m.
In this research, the cell morphology and physico-mechanical properties of HDPE/EVA/Rice hull hybrid foamed composites were investigated. For this aim, composites were prepared via melt mixing and ...then foamed using a compression molding method. Mechanical properties such as tensile strength, tensile and flexural modulus, and density were measured. Morphology of the samples was also evaluated by scanning electron microscopy (SEM). Results indicated that the tensile strength, tensile and flexural modulus, and density increased with the increase of rice hull content. However, with addition of blowing agent content and EVA content, mechanical properties and density of foamed composites decreased. Rice hull fibers acted as nucleating agents that substantially reduced cell size and increased cell density. In addition, EVA played an important role in foaming process by increasing the melt viscosity of the polymer matrix, in a way that samples with higher content of EVA have the highest cell density and the lowest cell size.
Applying acoustic panels made of natural fibers, due to their high biodegradable characteristics, light weight, low density, cheap price and non-toxicity, are proper alternatives to acoustic ...absorbers made of synthetic fibers. Considering their stance and vast applicability in industry, the possibility of producing them of natural palm fibers with sodium silicate adhesive of 10 and 20% in two 16 and 32 mm thicknesses, 350 and 450 kg/m3 densities, 50 and 100 mm particles length (strands), as variable factors in 16 types of matched panels with 3 repetitions is proposed in this article. The palm-trunk discs constituted the control sample. The effect of variables on sound absorption coefficient was assessed. The effect of variable thickness and adhesive percentage on all frequencies was significant and the effect of density variable on all frequencies except 250 and 2000 Hz was also significant. The effect of particle length was significant except at the 500 Hz frequency. The effects of all variables on porosity were significant. The results of this study suggest that by applying date palm-trunk (an agricultural waste) combined with sodium silicate adhesive, industrial environment-friendly panels can be produced with proper sound absorption coefficient in the field of acoustics. This 32-mm-thick panel was composed of 80% date palm-trunk particles of 50 mm length, 450 kg/m3 density, and 20% sodium silicate adhesive.
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