The aim of this study was to investigate the effect of using recycled polyethylene on the mechanical properties of PE-MDF composite. Saw dust as a filler at 30%and MAPE as coupling agent at two levels of 0 and 2 wt% were mixed in an internal mixer and the samples were prepared by injection molding method.. Mechanical properties such as tensile and flexural (Strength and Modulus) were measured. Morphology of composite was also evaluated by scanning electron microscopy (SEM). Although virgin polyethylene has better mechanical properties than once and twice recycled polyethylene, but with the addition of sawdust as filler consisting of recycled polyethylene composites mechanical properties significantly higher than that virgin polyethylene. The results of mechanical properties showed improvement by the addition of MAPE. The SEM micrographs showed that the use of twice recycled polyethylene and MAPE has led to better interactions between matrix and filler. The melt flow index (MFI) indicated that with increasing number of recycled polyethylene, melt flow index increased. Therefore with attention to the results of mechanical properties can be stated that by increasing the melt flow index had a positive effect on composite construction.

The present investigation is studied the effect of the replacement of different percentages of natural zeolite (Ze) pozzolan powder on the mechanical properties of recycled concrete made from coarse masonry recycled aggregates. In made concretes, natural aggregates were replaced with recycled coarse masonry aggregates at 25%, 50% and 100% levels. For improve the mechanical properties, natural zeolite was replaced by cement at 10%, 20% and 30% levels. In total, 195 standard cubic and cylindrical concrete samples in the 16 mixing designs were made and compressive strength tests at 7, 28 and 91 days, splitting tensile strength, modulus of elasticity and ultrasonic pulse velocity at 28 days of age were evaluated. the results showed that, at replacement levels of 20% natural zeolite with cement was had the greatest improvement in the mechanical properties of natural concrete but in combination with recycled aggregates, the replacement of 10% natural zeolite by cement was improved the mechanical properties of recycled concrete. also the results showed that, 10% of natural zeolite, using up to 50% of coarse masonry recycled aggregates, Improvement some mechanical properties of recycled concrete was showed relative to conventional concrete without pozzolan, but replace 100% coarse natural aggregates with recycled masonry, mechanical properties of recycled concrete have significantly decreased compared to natural concrete without pozzolan.

Mechanical properties and burning rate are very important parameters for solid propellants. In this work, the effects of quality and quantity of stabilizers as AkarditeII, 2-NDPA and CentraliteI on the Mechanical properties and burning rate of double-based is investigated. The results showed that, by CentraliteI increased mechanical properties of propellant and for AkarditeII and 2-NDPA stabilizers mechanical properties was lower than CentraliteI. Increasing the amount of AkarditeII decreased burning rate and increasing the amount 2-NDPA increased burning rate.

Salt crystallization is one of the most powerful weathering agents that may cause a rapid change in the mechanical properties of stones, and thus limit their durability. Consequently, determining the mechanical properties of stones due to salt crystallization is important for natural building stones used in marine environmental and mild climatic conditions, which expose excessive salt crystallization cycles. In this study, multivariate regression analysis was performed for estimating the mechanical properties of travertine building stones after salt crystallization test. For this purpose, 12 travertine samples were selected and their physical and mechanical properties (density, porosity, uniaxial compressive strength, Brazilian tensile strength, and P-wave velocity) were determined. Then salt crystallization test was carried out at sodium sulfate solution (Na2SO4) up to 50 cycles and, after every 5 cycles, the uniaxial compressive strength, Brazilian tensile strength and P-wave velocity of the samples were measured. Using data analysis, regression equations were developed for estimating the mechanical properties of deteriorated samples at any cycle of the salt crystallization test. In these equations, the mechanical properties of the samples after salt crystallization were considered to be the dependent variable, which is dependent on the independent variables of the number of salt crystallization cycles, initial mechanical properties of the stones and their porosities. The validity of the equations was verified with the mechanical properties data of a researcher for salt crystallization test. The results showed that regression equations are in good accuracy for estimating the mechanical properties of stones, and thus making a rapid durability assessment.

In this study، the effect of enzymatic refining with endoglucanase was investigated on the physical and mechanical properties of OCC pulp. Collected OCC pulps were pre-treated with different endoglucanse dosages (1u، 2u and 3u on o. d. pulp) under constant conditions and then refined at different levels. The effect of different enzyme dosages and refining levels were evaluated separately on the paper physical and mechanical of properties، as compared to control pulp (non treated pulp with enzyme). In unrefined pulps، the results have shown that adding enzyme up to 1u caused to improve the physical and mechanical properties as significant (confidence level of 95%)، compared to control pulp. However using more than uendoglucanase was resulted a significant decrease in both physical and mechanical properties. Achieved results from the effect of different enzyme dosages and refining levels showed that in refined pulps، increase of enzyme level caused to produce a bulky paper and decrease of mechanical properties. In general، the best physical and mechanical properties was obtained using 1u endoglucanase at different refining levels applied.

Molecular dynamics simulations have been performed to study the mechanical properties of hydrogen functionalized graphene. We find out that Young’s modulus and tensile strength of pristine graphene are in good agreement with experimental results. It is shown that hydrogen functionalization can considerably modify the mechanical properties of graphene. It is also found that the patterned orrandom hydrogen coverage have different effects on the mechanical properties of graphene. Using molecular dynamics simulation, we study the mechanical properties of hydrogen functionalized graphene under tension and shear deformations at constant room temperature. Young’s modulus and shear modulus, tensile and shear strengths and tensile and shear fracture strains are mechanical parameters that are calculated in order to investigate the mechanical properties of hydrogen functionalized graphene. Results show that in some cases, hydrogen coverage pattern is important independent of its coverage percentage. The underlying mechanisms were explained considering the difference between sp^2 and sp^3 hybridization.

In this study, the effect of mechanical reinforcement of glass fiber sizing on the transverse mechanical properties of the glass/epoxy composite, due to the significant impact of this region on the overall mechanical properties of reinforced composites with fibers, has been investigated. To predict the transverse elastic modulus and tensile strength of the glass/epoxy composite, a representative volume element (RVE) and a three-dimensional shell model are simulated respectively, in ABAQUS commercial software. Sizing mechanical properties are held non-homogeneous and non-uniform along its thickness in the simulation. Furthermore, sizing reinforcement is done by a Random-Distribution method using carbon nanotubes (CNTs). Different lengths, diameters and, volume fractions are considered for the CNTs in sizing reinforcement in this simulation, and then the results are compared. The comparison between the results obtained from simulation and available experimental data illustrates that the sizing simulated by non-uniform mechanical properties provides more precise results than the sizing assumed by constant mechanical properties. Also, it is shown that increasing in CNTs length or decreasing in their diameter, which are distributed in sizing, would lead to improving the transverse elastic modulus and tensile strength of the glass/epoxy composite.

Biodegradable porous scaffold polymers are good candidates for tissue engineering. In this research, a three-dimensional porous poly-lactic acid (PLA) scaffold was prepared using a Fused Deposition Modeling (FDM) including about 70% porosity. The study of the phases of primary filament and scaffold using the X-ray diffraction (XRD) test shows that no significant phase difference has been created due to the manufacturing process and the polymer retains its phases properties. The results of the mechanical properties evaluation by the compression test show that the mechanical properties of the scaffold are different in both the parallel and perpendicular directions of the Z axis during the printing, and the mechanical properties of the scaffold are of anisotropic property. Microstructural study by Scanning Electron Microscope (SEM) also shows that the morphology of scaffold porosities is different in two directions, and this is the main cause of anisotropic mechanical properties. Anisotropy of the mechanical properties of FDM produced scaffolds should be considered during load bearing applications in vivo.

A nanoparticle or an infinitesimal particle is usually defined as a particle of matter that has a diameter between 1 and 100 nanometers (nm). The properties of nanoparticles often differ significantly from larger particles of matter. Nanoparticles show different dislocation mechanics, which together with their unique surface structure, lead to different mechanical properties from bulk materials. Nowadays, by adding nanoparticles, the mechanical properties of composites are improved. Due to their small size, nanoparticles increase the surface area between the base material and the reinforcement and therefore improve the mechanical properties. The type of nanoparticle used, dimensions, weight percentage and the way of nanoparticle distribution are determining factors in improving mechanical properties. In the present study, while presenting the concepts related to nanocomposite, the effect of five different nanoparticles on the common mechanical properties considered by structural designers is investigated. The results show that the addition of nanoparticles up to a certain weight percentage improves the properties, and more than that amount sometimes has the opposite effect, one of the reasons for which is the clumping of nanoparticles.

In cold regions, freeze-thaw cycles are one of the most important agents affecting on the mechanical properties of stones and consequently their durability. Uniaxial compressive strength, Brazilian tensile strength and P-Wave velocity are among important mechanical properties in assessing the durability of the stones used in cold regions. As regards of determination these properties during the freeze-thaw cycles experiment is very time consuming and cumbersome, statistical relationships can be used to estimate the mechanical properties. In this study, a multivariate statistical model is presented for 15 samples of travertine, which can estimate uniaxial compressive strength, Brazilian tensile strength and P-Wave velocity in each cycle of the freeze-thaw experiment. In this model, mechanical properties after freeze-thaw cycles were considered to be the dependent variable that dependent on the variables of the initial mechanical properties, water absorption and the number of freeze-thaw cycle. The statistical tests results and also data from other researchers show that model presented is reasonably accurate in estimating uniaxial compressive strength, Brazilian tensile strength, P-Wave velocity and consequently their durability of the travertines in each cycle of the freeze-thaw experiment.