2019-01-16T05:28:59Z
http://macs.journals.semnan.ac.ir/?_action=export&rf=summon&issue=77
Mechanics of Advanced Composite Structures
MACS
2423-4826
2423-4826
2016
3
2
The Effect of Processing Conditions on the Mechanical Properties of Polypropylene/Mesoporous Silica-Hydroxyapatite Hybrid Nanocomposites
A.R.
Albooyeh
S.
Tarahomi
A.B.
Fereidoon
Z.
Taherian
This work focused on the influence of processing conditions on the mechanical properties of polypropylene (PP) and PP/mesoporous silica-hydroxyapatite (PP/MCM-41-HA) hybrid nanocomposites. The mechanical properties of PP were enhanced by adding MCM-41-HA nanoparticles. Neat PP and hybrid nanocomposites based on PP, containing maleic anhydride-grafted polypropylene (PP-g-MA) and MCM-41-HA, were prepared using the melt intercalation technique in an internal mixer. To optimize the processing conditions, both mixing temperature and rotor rotational speed were varied. Tensile and flexural tests were performed to evaluate some mechanical characteristics (stress-strain curves, tensile strength, tensile modulus, strain at rupture, flexural strength. and flexural modulus) of both the neat PP and PP/ MCM-41-HA hybrid nanocomposite materials. The results showed that two of the materials’ mechanical properties were most affected by two preparation parameters: shear rate and the distribution process of nanocomposites were found to be optimized using a mixing temperature of 180° C and a rotor rotational speed of 100 rpm to achieve the best mechanical properties. Under these conditions, the best mixing time was 3 min according to the torque diagram. Moreover, the PP/MCM-41-HA hybrid nanocomposite demonstrated a sensible enhancement of mechanical properties over neat PP.
Nanocomposite
Experimental Study
Mechanical properties
Mesoporous silica
Hydroxyapatite
2016
11
01
73
82
http://macs.journals.semnan.ac.ir/article_469_4ffab0e68480aa62b0558f5ca48a41aa.pdf
Mechanics of Advanced Composite Structures
MACS
2423-4826
2423-4826
2016
3
2
The Effect of External Skin on Buckling Strength of Composite Lattice Cylinders Based on Numerical and Experimental Analysis
M.R.
Zamani
S.M.R.
Khalili
Currently, lattice composite structures have many applications in aerospace industries. The present research analyzed the effect of an external skin consisting of a lattice’s cylindrical shell on the buckling strength of composite materials, both numerically and experimentally. Two classes of specimens, with and without external skins, were fabricated using the filament winding process. To find the buckling strength of the fabricated samples, tests were carried out. For validation of the experimental results, the finite element method was used to test the shells under the same testing conditions. The results of the experimental and numerical tests showed good agreement with one another, revealing that the lattice cylindrical shell specimen with the outer skin had a much higher buckling strength than the one without the outer skin (≈50%). The added weight of the outer skin was negligible compared to the overall weight of the lattice cylindrical shell, and the external skin had a tremendous positive effect on the buckling strength to weight ratio of the lattice composite structures.
Lattice structures
Buckling
FEM
Stiffened composite cylindrically shell
2016
11
01
83
87
http://macs.journals.semnan.ac.ir/article_470_7a73ba26d1aeb2693f5b846f4938339c.pdf
Mechanics of Advanced Composite Structures
MACS
2423-4826
2423-4826
2016
3
2
Analytical Solution for Sound Radiation of Vibrating Circular Plates coupled with Piezo-electric Layers
K.
Khorshidi
M.
Pagoli
In the present study, the classical plate theory (CPT) was used to study sound radiation of forced vibrating thin circular plates coupled with piezoelectric layers using simply supported and clamped boundary conditions. The novelty of the study consists of an exact closed-form solution that was developed without any use of approximation. Piezoelectric, electrical potential loaded in the transverse direction satisfied the electric boundary conditions (open circuit) and Maxwell's electricity equation. It was assumed that no fluid loading occurred on the plate structure. The sound pressure and the sound power of the radiator were analytically obtained in a far field by using the Rayleigh integral. The proposed analytical method was validated using available data from the literature. Additionally, a few 2-D plots of the directivity pattern were illustrated for thin circular plates coupled with piezoelectric layers. Finally, the effect of boundary conditions, piezoelectric thickness, and the piezoelectric layer on the acoustical parameters were examined and discussed in details.
Circular plates
Sound power
Classical plate theory
Piezoelectric layer
2016
11
01
89
98
http://macs.journals.semnan.ac.ir/article_471_12415b95cd7424ae15936b88bcf3e919.pdf
Mechanics of Advanced Composite Structures
MACS
2423-4826
2423-4826
2016
3
2
Size-dependent Effects on the Vibration Behavior of a Ti-moshenko Microbeam subjected to Pre-stress Loading based on DQM
M.
Mohammadimehr
H.
Mohammadi Hooyeh
H.
Afshari
M.R.
Salarkia
In this paper, size-dependent effects on the vibration behavior of Timoshenko microbeams under pre-stress loading embedded in an elastic foundation, using modified strain gradient theory (MSGT) and surface stress effects, were studied. To consider the surface stress effects, the Gurtin–Murdoch continuum mechanical approach was employed. Using Hamilton’s principle, the governing equations of motion and boundary conditions were obtained and solved numerically using the differential quadrature method (DQM). The effects of pre-stress loading, surface residual stress, surface mass density, Young’s modulus applied to the surface layer, three material length scale parameters, and the elastic foundation coefficients were investigated. For higher aspect ratios, this study found that the effect of the pre-stress loading was negligible for higher modes. Considering size-dependent effects led to increase the stiffness of the matrix and enhance the dimensionless natural frequencies of the Timoshenko microbeam. The MSGT results were higher than those found using other theories. In addition, this research discovered that there were negligible surface stress effects with each of the three material length scale parameters.
Size dependent effect
Pre-stress loading
DQM
Vibration behavior of Timoshenko microbeam
2016
11
01
99
112
http://macs.journals.semnan.ac.ir/article_472_e09505a5962654ff4e6f2518a26d7319.pdf
Mechanics of Advanced Composite Structures
MACS
2423-4826
2423-4826
2016
3
2
Mechanical Properties of CNT-Reinforced Polymer Nano-composites: A Molecular Dynamics Study
M.
Farhadinia
B.
Arab
J.E.
Jam
Understanding the mechanism underlying the behavior of polymer-based nanocomposites requires investigation at the molecular level. In the current study, an atomistic simulation based on molecular dynamics was performed to characterize the mechanical properties of polycarbonate (PC) nanocomposites reinforced with single-walled armchair carbon nanotubes (SWCNT). The stiffness matrix and elastic properties such as Young’s modulus, shear and bulk moduli, and Poisson’s ratio for the pure PC and PC/CNT nanocomposites were estimated using the constant-strain method. In this research, this method was used for the first time to investigate the effects of different parameters, such as the effects of weight fraction and aspect ratio of CNTs on the elastic properties of PC/SWCNT nanocomposites. From the computational results, the elastic moduli of PC/CNT nanocomposites increased with increasing the amount of incorporated CNTs, while their aspect ratio (<em>l/d</em>) also increased. A significant increase in the elastic modulus (41.2%) was observed, even with the addition of a small quantity (2.4 wt%) of SWCNTs. Upon addition of about 6.9 wt% of SWCNTs, the elastic modulus increased by almost 52%.
Carbon Nanotubes
Polymer nanocomposites
Mechanical properties
Molecular Dynamics
2016
11
01
113
121
http://macs.journals.semnan.ac.ir/article_473_a19264405e2651451ef26d58515ec074.pdf
Mechanics of Advanced Composite Structures
MACS
2423-4826
2423-4826
2016
3
2
Static and Free Vibration Analyses of Functionally Graded Nano-composite Plates Reinforced by Wavy Carbon Nanotubes Resting on a Pasternak Elastic Foundation
R.
Moradi Dastjerdi
G.
Payganeh
S.
Rajabizadeh Mirakabad
M.
Jafari Mofrad-Taheri
In this study, static and free vibration analyses of functionally graded (FG) nanocomposite plates, reinforced by wavy single-walled carbon nanotubes (SWCNTs) resting on a Pasternak elastic foundation, were investigated based on a mesh-free method and modified first-order shear deformation theory (FSDT). Three linear types of FG nanocomposite plate distributions and a uniform distribution of wavy carbon nanotubes (CNTs) were considered, in addition to plate thickness. The mechanical properties were by an extended rule of mixture. In the mesh-free analysis, moving least squares (MLS) shape functions were used for approximation of the displacement field in the weak form of a motion equation, and the transformation method was used for imposition of essential boundary conditions. Effects of geometric dimensions, boundary conditions, the type of applied force, and the waviness index, aspect ratio, volume fraction, and distribution pattern of CNTs were examined for their effects on the static and frequency behaviors of FG carbon nanotube reinforced composite (CNTRC) plates. Waviness and the distribution pattern of CNTs had a significant effect on the mechanical behaviors of FG-CNTRC plates, even more than the effect of the CNT volume fraction.
Static
Free Vibration
Wavy carbon nanotube
Nanocomposite plates
Mesh-free
2016
11
01
123
135
http://macs.journals.semnan.ac.ir/article_474_6d9f04323ad9f8ac8837f55116ae4c88.pdf
Mechanics of Advanced Composite Structures
MACS
2423-4826
2423-4826
2016
3
2
Modeling of Hygrothermal Damage of Composite Materials
R.B.A.
Ouled Ahmed
S.
Chatti
H.
Ben Daly
Composite materials have been used extensively in various applications, such as mechanical engineering, aerospace engineering, and aviation thanks to their interesting mechanical properties. However, a substantial drawback in the use of such composite materials is that they absorb a significant amount of moisture when exposed to severe hygrothermal conditions. This factor dramatically affects the composite material’s various physical and mechanical properties. This paper proposed a new model to predict the amount of moisture absorbed by a composite polyester/glass fiber composite material before and after hygrothermal damage. Two damage models were proposed and implemented in ABAQUS. A numerical simulation was used to estimate hygrothermal stresses in a composite plate. The results showed that the moisture absorption followed a Fickian behavior; if the temperature was low, the plate would be damaged, but the moisture diffusion rate accelerated when the hygrothermal parameters (temperature and humidity) were high. Additionally, the magnitude of residual stress, which was at its maximum at the beginning of the absorption, started to decrease until reaching zero when the plate was saturated.
composite
Fick’s law
Hygrothermal stress
Damage law
2016
11
01
137
144
http://macs.journals.semnan.ac.ir/article_475_f360fe88b6c8ab7e30a27aec1b6b192b.pdf