In the present study, the effect of MAPP as the compatibilizer on the mechanical properties of wood-flour polypropylene composites was investigated using Dynamic mechanical analysis (DMA). Composites were made at 25 and 50 percent (by weight) fiber contents and 1 and 2 percent compatibilizer. Controls were also made at the same fiber contents but without the compatibilizer. Static mechanical tests including tensile and bending tests were performed. Temperature scans in the range of -60° to +120°C was done. Results indicated improvements in the mechanical properties as a result of adding comatibilizer. MAPP had negligible effects on the main transitions while the effect of fiber content on the intensity and temperature of alpha transition was almost proportional to the fiber content. Glass transition remained unchanged when adding MAPP while an increase in fiber content slightly shifted this transition to lower temperatures. mechanical loss factor spectra showed that above +40°C energy loss became more pronounced when compatibilizer was absent.

Aging resulting in stabilization is one of the most important and advanced aspects of polymer chemistry. Solid propellants as polymer-based materials deal with aging process as well. This research work has evaluated Dynamic mechanical analysis (DMA) for characterization of composite propellant samples during an accelerated aging program. Although there are only a few reports in the open literature concerned with using DMA in aging studies they are not reported inside the country. In this method, the changes in storage module (E) and damping (tand) of the sample during the aging time versus temperature are investigated. Accelerated aging tests at 25, 45, 60, and 70°C were performed for the maximum 8000 h. Finally, we observed that damping efficiency decreases about 12% as a result of thermal aging. The resulted data may be used to determine the aging rate, service time and decomposition mechanism during the rocket storage.

In this study, effect of MAPE (maleic anhydride polyethylene) as the compatibilizer ‎on the mechanical properties of wood-flour polyethylene composites has been ‎investigated by suing Dynamic mechanical analysis (DMA). Composites were made ‎at 25% and 50% by weight fiber contents and 1% and 2% compatibilizer respectively. ‎Controls were also made at the same fiber contents without the compatibilizer. Static ‎mechanical tests including tensile and bending tests were performed. Temperature ‎scans in the range of -110 to +100°C was also conducted. Results indicated ‎improvements in the mechanical properties due to the compatibilizer addition. Storage ‎modulus values were higher in the case of coupled composites especially at 50% fiber ‎loading. Glass transition was hard to detect in all composite systems while increasing ‎fiber content slightly shifted alpha transition to higher temperatures. MAPE had ‎negligible effects on the main transitions but the effect of fiber content on the ‎intensity and temperature of alpha transition seemed to be proportional to the fiber ‎content. mechanical loss factor spectra showed that at 50% fiber content, the ‎compatibilizer caused a reduction in tan#d values indicating less energy loss when the ‎compatibilizer was present‏.‏

Polyvinylidene fluoride polymer poses unique properties such as piezoelectric and high mechanical, thermal, and chemical resistance due to the consisting of the most electronegative element, fluorine, in its combination. In this paper, molecular Dynamics simulation of amorphous polyvinylidene fluoride polymer containing polarized monomers is utilized to study its mechanical properties. Firstly, by using tensile test, elastic modulus and ultimate stress are determined and their changes due to temperature and strain rate change are studied. Then, by using Dynamic mechanical analysis, tensile and shear Dynamic complex modulus are calculated and their changes are studied while strain rate changes. This is for the first time that Dynamic mechanical analysis is simulated by molecular Dynamics. In addition to determining the viscoelastic properties of the material, straight forward elimination of temperature disturbances due to the sinusoidal pattern of stress and strain functions in terms of time is one of the advantages of the Dynamic mechanical analysis. Consistency between simulated and actual trends shows the efficiency of the proposed model.

In this article, Dynamic response of the thick cylindrical shell subjected to mechanical moving pressure has been investigated. The temperature distribution varies with respect to the thickness and moving along the length of the thick shell. First, the equations of motion have been derived using the Hamilton’s principle and the first order shear deformation theory. These equations are the systems of partial differential equations with constant variables. They have been solved using the converted ordinary differential equations under various load conditions. The Results of the present analytical method have been verified by comparing with finite element results using the ABAQUS software. The Comparison of the results with the finite element method shows that the first order shear deformation theory can predict the Dynamic response of the thick cylindrical shell successfully.

The role of a kind of plasticizer (OLA8) and two types of nucleating agents (LAK301 and PDLA) on the physical, mechanical and thermal behaviors of poly- lactic acid (PLA) were studied by differential scanning calorimetry (DSC), Dynamic mechanical thermal analysis (DMTA) and tensile test. The results show that the OLA8 is an efficient plasticizer for PLA. this is because in the presence of 20wt% of OLA8 the elongation at break of PLA promoted. Also adding plasticizer to PLA causes to drop down both enthalpy and crystallinity unlike the presence of nucleating agent. For example the enthalpy and crystallization of a sample with composition of 20% OLA8-5%PDLA-2.8%LAK is half of than that of pure PLA. At constant plasticizer content, addition nucleating agents in different types and quantities causes to promote a little bit in enthalpy and crystallinity. in the presence of both plasticizer and nucleating agent (20%OLA8-5%PDLA-2.8%LAK) half time crystallization as 0.46" min was recorded. In the same composition the glass transition temperature reduces 10 °C relation to pure PLA.

This work is conducted to obtain mechanical properties of microtubule. For this aim, interaction energy in alpha-beta, beta-alpha, alpha-alpha, and beta-beta dimers was calculated using the molecular Dynamic simulation. Force-distance diagrams for these dimers were obtained using the relation between potential energy and force. Afterwards, instead of each tubulin, one sphere with 55 KDa weight connecting to another tubulin with a nonlinear connection such as nonlinear spring could be considered. The mechanical model of microtubule was used to calculate Young’s modulus based on finite element method. Obtained Young’s modulus has good agreement with previous works. Also, natural frequency of microtubules was calculated based on finite element method.

The main purpose of this study is to investigate nonlinear buckling analysis of Functionally Graded (FG) cylindrical shells under uniform axial compressive loads by Dynamic relaxation (DR) method. The mechanical properties of shell vary continuously throughout the thickness direction according to the power-law, exponential function and the Mori-Tanaka distribution. The poisson’s ratio of the FG cylindrical shell is constant for power-law and exponential function. But in the Mori-Tanaka distribution variations of poisson's ratio is determined as a function of the thickness direction. The incremental form of nonlinear formulations are based on first order shear deformation theory (FSDT) and large deflection von Karman equations. The DR method combined with the finite difference discretization technique is employed to solve the equilibrium equations. Some comparison study is carried out to compare the current solution with the results reported in the literature and the ones obtained by the Abaqus finite element software for the isotropic cylindrical shells. Finally, numerical results are presented for critical buckling load with various boundary conditions, grading indices, radius -to- thickness ratio, length -to- radius ratio and variation of poisson’s ratio.