نشریه علوم و فناوری کامپوزیت
سال نهم شماره 4 (پیاپی 34، زمستان 1401)

The FSP is a method for solid state processing of metal alloys. FP4M milling machine and non-consumable rotary-tools were used to create the necessary heat and further mix copper with titanium-dioxide powder. The base plate is made of copper with a purity of 99.9%. The heat created during the process on the copper piece and the titanium-dioxide nanoparticles in the groove leads to metallurgical changes in the microstructure of the base metal and leads to changes in the size and shape of the grains. The samples were subjected to metallography and microstructure investigations by OP, XRD, corrosion and wear tests. The results show that in the HAZ area, the grains were in the form of a fine grain structure of copper solid solution, containing twin regions with an average grain size of 14, but in the process area, the grains were formed as a distorted and disturbed structure of copper solid solution. The average friction coefficient in the base copper wear diagram is less than one. By matching with the corrosion graph, the base copper sample has better corrosion resistance.

Lead-acid batteries are a significant part of the global battery market; however, due to limited life of these batteries, we are faced with major environmental challenges associated with lead-acid battery waste. One of their main components is the separator. In addition to polyethylene and silica, the separator of these batteries also contains lead compounds. In this research, lead-acid battery separator and polyethylene were used as a matrix for preparing a composite that could improve polyethylene's mechanical properties due to the presence of silica. Samples of HDPE and LLDPE with 5% to 15% lead-acid battery separator were prepared and their mechanical and thermal properties were evaluated and compared. By analyzing the DSC results, the type of polyethylene in the battery separator, HDPE, was determined. By adding the battery separator to HDPE matrix, elastic modulus increased by about 22% and bending modulus by about 55%. For LLDPE elastic modulus increased by approximately 35%. The yield strength of the sample, with HDPE matrix containing 15% separator has increased from 25.1 MPa to 28 MPa, and for the sample, with LLDPE matrix containing 15% separator, yield strength increased from 11.9 MPa to 13.7 MPa. Hardness and modulus for 15% of the separator are at maximum value. Consequently, 15 wt.% separator is an optimal value to improve samples' mechanical properties.

The hard polyurethane foams are one of the most consumed polymer foams as thermal insulation. Excessive consumption of these materials and their non-biodegradability is one of the human concerns in the field of environmental considerations. There are different ways to improve the biodegradability of polymers. The use of natural biodegradable materials in the polymer matrix is one of the solutions. Here, for the first time, rice husk, which is one of the abundant agricultural wastes in the country, has been used in polyurethane insulation foams. First, the rice husks were ground and sieved. Then, these materials were divided into two groups. One group of these materials was subjected to alkaline treatment. Both alkaline and non-alkaline treatment groups were subjected to isocyanate modification. For isocyanate modification, 20% by weight of isocyanate compounds were used. Both alkaline treat mentation and isocyanate modification methods were investigated using an infrared spectroscopy test. Then, the modified rice husks were added to the polyurethane foams at a rate of 5% by weight. Finally, the mechanical and insulating properties of the foams were evaluated. The results showed that both groups of isocyanate-modified rice husks, non-alkaline treatment, and alkaline treatment improved the compression strength properties of the polyurethane foams up to 89%. Also, the insulation properties of the foams are improved, too. improved, too.

The present research has studied the effect of adding perlite and natural rubber nanoparticles with various weight percentages on the tensile modulus and impact strength of polypropylene. For this purpose, different samples were produced and tested using an internal mixer based on the standards of tensile and impact tests. Also, by using of response surface methodology (RSM), the role of input parameters on the responses was investigated in order to achieve optimal mechanical properties and predict these properties with mathematical models in the form of central composite five-level design (CCD). In addition, the SEM test was used to observe the changes made in the microstructure of the samples. The results showed that the addition of 7 wt.% of pearlite nanoparticles to the matrix containing 20 wt.% of natural rubber, the value of the tensile modulus increased by 11.27% and the impact strength by 52.01% compared to the addition of 3 wt.% of pearlite nanoparticles to the same matrix. The results of multiobjective optimization proved that the optimal weight percentage of pearlite nanoparticles and natural rubber was 4.04 and 35.26% wt. respectively. Is. In this case, the highest value obtained for tensile modulus was 508.04 MPa and impact strength was determined to be 108.52 J/m. By observing the SEM images, it was concluded that the change in the size of the elastomeric phase due to the use of different weight percentages of reinforcements has caused the results of the mechanical properties of the samples to differ from each other.

In this paper, the parametric analysis of the impact on cylindrical sandwich shells with the FML face sheet and functionally graded core using a new shell theory is discussed. In this research, two new, simple and engineering models have been presented to predict the history of the contact force caused by a quasi-static transverse impact by an elastic and isotropic impactor in the shape of a sphere, with a low speed, to a composite cylindrical shell. These two models are the half-sine model (or H-S) and the improved mass and spring model with two degrees of freedom (or IS-M). In the H-S model, the maximum contact force and contact duration have been extracted analytically. In the IS-M model, first the mass and the effective stiffness of the shell at the contact point are calculated analytically, then using the successive method and reaching convergence, the modified contact stiffness is obtained. Validation of the present research results was done by comparing the theoretical and experimental results of other researchers and the results of the ABAQUS software, and a good match has been achieved. The results show that the more accurately the effect of (z/R + 1) terms are calculated, the higher the accuracy of estimating the impact response.

Compared to mechanical joining methods, adhesive bonded joints have uniform stress distribution, good fatigue performance and better weight reduction effect. Some failures in the adhesive bonded joints are caused by the presence of contamination and inappropriate roughness in the joint surfaces. In this study, the effect of different surface treatment on the mechanical behavior of the composite/aluminum adhesive joint in the mode I of fracture is investigated by using Double-cantilever beam specimen. Surface treatment has been done with three methods of Peel Ply Processing, Sanding and Laser for composite adherent and two methods of Sanding and Laser for aluminum adherent. In the laser surface treatment method, the transverse distance of the grooves and the spots diameter are fixed, and the scanning speed and power of the machine are variable. The surface roughness measurement of the adherents shows the increase of the surface roughness up to a certain value of the laser energy density, but after that the roughness has decreased due to the melting of the adherent surface. The results show an increase of 13.43% and 7.46% in the critical strain energy release rate of the mode I of fracture using the laser surface treatment method compared to the Sanding method and the Peel Ply Processing method, respectively. Also, examination of the fracture surface of the joint shows an increase in the failure mode of fiber tearing at the joint surface with the correct selection of laser parameters, which has improved the strength of the joint.