نشریه علوم و فناوری کامپوزیت
سال دهم شماره 3 (پیاپی 37، پاییز 1402)

Composites are combined with at least two materials; one is considered as the base material and later is used to improve the material properties. This study is also about one of the widely used composites so-called aluminium metal matrix composites (Al-MMC) and additional reinforcing particles, including silicon carbide (SiC). The main features of such composite are high hardness and strength, as well as lightweight.The main disadvantages are low machinability and high wear in cutting tools. Several studies have been conducted to improve the machinability of MMCs. The literature review in this domain denotes that limited studies have yet been conducted on the effects of different cooling methods, especially cryogenic cooling and related strategies, on the wear and tool life in the machining of MMCs. Therefore, in this study, the effects of cutting parameters and cryogenic cooling on the tool wear in the machining of A356-10%SiC were studied. Based on the statistical analysis, it was observed that the effects of cutting parameters and cryogenic cooling parameters on the tool wear was significant (R2=0.97, and a robust mathematical relationship exists between tool wear and the studied parameters. Moreover, compared with previous studies, it was observed that tool life under cryogenic conditions was increased by around 26% compared to readings made under dry conditions.

Nondestructive evaluation of mechanical properties and health monitoring of composite structures is of great importance. The aim of this research was to propose a nondestructive evaluation method based on the propagation of Lamb waves to investigate the matrix cracking damage in laminated cross-ply composites. For this purpose, after developing the finite element model of a glass/epoxy composite, the Lamb wave behavior was studied in two antisymmetric (A0) and symmetric (S0) modes with different excitation frequencies. The dispersion curves of the A0 and S0 modes of the Lamb wave are then obtained by considering different crack densities. It was observed that the effect of matrix crack density and the loss of mechanical properties of the cross-ply composites on the phase velocity of the S0 Lamb wave mode was higher than that of the A0 mode. Furthermore, the detection of matrix cracking was better performed using the Lamb wave velocity at high frequencies close to the cut-off frequency. It was observed that the cut-off frequency decreased by increasing the crack density, and the drop in the Lamb wave velocity increased by increasing the number of 90° layers in the cross-ply composite. It was concluded that the Lamb wave propagation simulation method can be used as a virtual laboratory for nondestructive evaluation of composites and detection of matrix crack density in them.

Due to its biocompatibility and biodegradability, magnesium has become a very suitable candidate for orthopedic implant applications. However, its high corrosion rate leads to rapid deterioration in corrosive environments, resulting in premature failure of the implant before sufficient bone healing. In this regard, surface modifications are required to improve corrosion resistance. This research investigates the effect of two surface modifications, shot peening and electrospinning, on the corrosion properties of magnesium/hydroxyapatite composite. Shot peening was performed using glass beads at an Almen intensity of 0.3 mmN and with 100٪ coverage on the surface of the composite. Electrospinning was carried out using Polycaprolactone (PCL) nanofibers at 18 kV for 30 minutes. Tensile-compressive tests were performed on the composite specimens. Also, pH monitoring and weight loss tests were conducted on the shot peened and electrospun samples. The results show that electrospinning decreased the corrosion rate of magnesium by 75٪ and 40٪ after 1 day and 7 days of immersion, respectively. Shot peening also reduced the corrosion rate by 35٪ and 20٪, respectively. Electrospinning reduced the corrosion rate by limiting the contact surface area between the corrosive solution and magnesium due to its high specific surface area for calcium-phosphate absorption. Shot peening, on the other hand, delayed the corrosion by accelerating the formation of a passive layer, leading to increased corrosion resistance in short periods.

In this research, with the aim of investigating the effect of temperature on the performance of adhesive, riveted and composite glass/epoxy joints, the factors affecting this joint are studied. After checking the parameters, preparing the surface of the connection area using sandpaper on two levels using sandpaper with grain numbers of 220 and 400 and also controlling the thickness of the adhesive layer on two levels of 0.13 and 0.26 mm. The meter and the type of drill used to make holes on both surfaces were selected using a saw drill and a wood drill for rivet connection. The integration of selected parameters of two adhesive and riveted joints is considered in order to investigate the combined joint. In this regard, the experimental design using the Taguchi method has been carried out in the Minitab test design software. The purpose of conducting the experimental part of this research, as mentioned in the previous lines, is to obtain optimal joints according to the defined parameters and levels in order to set a standard and compare with the values obtained after performing the test on the mentioned joints under the effect of 80 It is the degree Celsius applied to the samples for four hours. In order to bring the results closer to the industrial conditions, we connected a number of adhesive, riveted and combined samples using the optimal levels of parameters defined for each of them, based on the zigzag arrangement of four rivets along the width of the area, which

Obtaining stress values in spherical shell of a thin-walled composite multi-layer vessel in a completely analytical way and independent of numerical methods in solving the equations is a subject that has not been investigated so far. In this article, using a fully analytical solution based on classical shell theory, the stress values in each layer of the spherical shell are obtained. In this solution method, by using equilibrium equations, Hooke's law, strain-displacement and curvature-displacement relations, the governing equations of general composite shells of revolution are extracted and then the governing equations of a symmetric spherical shell are obtained. In the following, using displacement and rotation consistency equations, forces and stresses at the intersection of the spherical and cylindrical composite shell are calculated, and then the longitudinal and circumferential stresses due to internal pressure are extracted in each layer. Finally, the results are compared with the results of the finite element numerical solution and it is shown that the stress values obtained from the analytical results are in good agreement with the results of the numerical solution and it is possible to use the results of this analytical solution to make optimally designed composite vessels.

This study aimed to propose an NDE method based on the guided wave propagation for assessing the thickness loss (corrosion) in the metal pipes coated with composites. First, the finite element model of a steel pipe with the thickness of 4 mm and diameter of 200 mm coated with a layered composite material was developed, in which the composite coating constituted by the chopped strand glass fiber mat and woven roving glass fiber cloth layers. Then, the fundamental antisymmetric guided wave mode with the frequency of 100 kHz was propagated in the longitudinal direction of the structure and the phase velocity of the propagated wave was measured in specimens with different corrosion extent in the steel pipe. In the first step, a uniform corrosion was induced throughout the pipe, and in the next step, it was induced in a part of the pipe with a specific length and circumferential angles of 90, 180 and 360 degrees. It was shown that the reduction in the wave phase velocity in the corroded regions compared with the intact regions was between 9% to 33% for different corrosion extents. Besides, the detection of the corrosion in the steel pipe and its location and extent was properly performed using the guided wave propagation method. It was concluded that the simulated guided wave propagation method can be used as a virtual lab for the development of methods for nondestructive evaluation of pipes coated with composites and detection of the location and extent of corrosion in them.