Lianhua Ma¹, Qingsheng Yang²

CMC-Computers, Materials & Continua, Vol.40, No.2, pp. 79-98, 2014, DOI:10.3970/cmc.2014.040.079

Abstract Honeycombs are widely used in aerospace structures due to their low density and high specific strength. In this paper, effective electromagnetic properties of irregular honeycombs are investigated, by using the three dimensional homogenization theory and corresponding computational procedure. This homogenization method, being the extension of two-scale asymptotic approach, is employed to determine the expressions of the effective dielectric permittivity, magnetic permeability and electrical conductivity. To verify and validate the proposed model and procedure, effective permittivities of a typical irregular honeycomb are studied and compared with those of semi-empirical formulae. Moreover, the effect of geometry of honeycomb's unit cell on effective… More >

Leiting Dong¹, Ahmed S. El-Gizawy², Khalid A. Juhany², Satya N. Atluri³

CMC-Computers, Materials & Continua, Vol.40, No.1, pp. 49-78, 2014, DOI:10.3970/cmc.2014.040.049

Abstract In this study, a simple 4-node locking-alleviated mixed finite element (denoted as CEQ4) is developed, for the modeling of homogeneous or functionally graded or laminated thick-section composite beam structures, without using higher-order (in the thickness direction) or layer-wise zig-zag theories of composite laminates which are widely popularized in current literature. Following the work of [Dong and Atluri (2011)], the present element independently assumes a 5-parameter linearly-varying Cartesian strain field. The independently assumed Cartesian strains are related to the Cartesian strains derived from mesh-based Cartesian displacement interpolations, by exactly enforcing 5 pre-defined constraints at 5 pre-selected collocation points. The constraints are… More >

Y. L. Liu¹, N. Hu², H. Xu³, H. Ning¹, L. K. Wu¹

CMC-Computers, Materials & Continua, Vol.40, No.1, pp. 1-20, 2014, DOI:10.3970/cmc.2014.040.001

Abstract A real-time monitoring technique for local plasticity using Lamb waves was developed. Tensile test of a thin aluminum plate with a circular hole where high stress concentration was induced was conducted to verify this technique. During the tensile test, a series of wave signals passing through the local plastic region were collected using a directional actuator/sensor set to monitor plasticity evolution. A pulse compression technique was used to process the wave signals. With the increase of tensile stress in the specimen, the amplitude changes of S₀ and A₀ modes were obtained and the difference of Lamb wave signals was further… More >

A.I. Dimitriadis¹, N.V. Kantartzis¹ and T.D. Tsiboukis¹

CMC-Computers, Materials & Continua, Vol.39, No.3, pp. 231-265, 2014, DOI:10.3970/cmc.2014.039.231

Abstract The most important surface susceptibility models for the electromagnetic characterization of periodic metafilms, based on the dipole approximation method, are systematically analyzed in this paper. Specifically, two well-known techniques, which lead to a set of local effective surface parameters, are investigated along with a new dynamic non-local modeling algorithm. The latter formulation is properly expanded, in order to be applicable for any arbitrary periodic metafilm, irrespective of its way of excitation. The featured schemes are then directly compared toward their ability to efficiently predict the reflection and transmission properties of several lossless and lossy metafilms. Their outcomes are carefully verified… More >

Linsen Zhu¹, Jiang Zhou², Xuejun Fan²

CMC-Computers, Materials & Continua, Vol.39, No.2, pp. 113-134, 2014, DOI:10.3970/cmc.2014.039.113

Abstract In this paper, a damage mechanics-based continuum theory is developed for the coupled analysis of moisture vaporization, moisture absorption and desorption, heat conduction, and mechanical stress for a reflow process in microelectronic devices. The extremely compliant film has been used in wafer level lamination process. Such a soft film experiences cohesive rupture subjected to moisture absorption during reflow. The numerical simulation results have demonstrated that vapor pressure due to moisture vaporization is the dominant driving force for the failures. The correlation between the vapor pressure evolution and the film rupture observed from the experiments have been established through two case… More >

Jingguo Yan¹, Xudong Wang¹, Man Yao^1,2, Ning Hu^3,4

CMC-Computers, Materials & Continua, Vol.39, No.1, pp. 73-84, 2014, DOI:10.3970/cmc.2014.039.073

Abstract Electronic structure and magnetism of the rare-earth metals Ac and Th doped Fe₃O₄ Fe_1-xRe_xFe_2-yRe_yO₄(Re=Ac, Th; x=0, 0.5, 1; y=0, 0.5, 1.0, 1.5, 2.0) are investigated by first-principle calculations. AcFe₂O₄, FeAc₂O₄ and ThFe₂O₄ are found to be II B-type half-metals. The large bonding-antibonding splitting is believed to be the origin of the gap for AcFe₂O₄, FeAc₂O₄ and ThFe₂O₄, resulting in a net magnetic moment of 9.0μ_B, 4.0μ_B and 8.1μ_B, respectively, compared with 4.0μ_B of Fe₃O₄. Also, the conductance of AcFe₂O₄ and ThFe₂O₄ are both slightly larger than that of Fe3O4. It can be predicted that the new rare-earth half-metals AcFe₂O₄ and… More >

Meng-Kao Yeh¹, Chia-Shien Liu², Chien-Chang Chen³

CMC-Computers, Materials & Continua, Vol.39, No.1, pp. 3-20, 2014, DOI:10.3970/cmc.2014.039.003

Abstract The dynamic instability of rectangular graphite/epoxy composite plates under parametric excitation was investigated analytically and experimentally. In analysis, the dynamic system of the composite plate, obtained based on the assumedmodes method, is a general form of Mathieu’s equation, including parametrically excited terms. The instability regions of the system, each separated by two transition curves, were found to be functions of the modal parameters of the composite plate and the position and the excited amplitude of the electromagnetic device on the composite plates. The fiber orientation, the aspect ratio and the layer numbers of the composite plates were varied to assess… More >

Branden B. Kappes¹, Cristian V. Ciobanu²

CMC-Computers, Materials & Continua, Vol.38, No.1, pp. 1-16, 2013, DOI:10.3970/cmc.2013.038.001

Abstract Controlling the bandgap of carbon nanostructures is a key factor in the development of mainstream applications of carbon-based nanoelectronic devices. This is particularly important in the cases where it is desired that the carbon nanostructures are the active elements, as opposed to being the conductive leads between other elements of the device. Here, we report density functional theory calculations of the effect of silicon impurities on the electronic properties of carbon nanotubes (CNTs). We have found that Si adatoms can open up a bandgap in intrinsically metallic CNTs, even when the linear density of Si atoms is low enough that… More >

Yongze Cao¹, Guojian Li¹, Qiang Wang^1,2, Xiaoguang Wang³, Jiaojiao Du¹, Jicheng He¹

CMC-Computers, Materials & Continua, Vol.37, No.3, pp. 195-203, 2013, DOI:10.3970/cmc.2013.037.195

Abstract The Fe₆₀Ni₄₀ (in atomic %) polycrystalline thin films with 90 nm thickness were prepared on 200 °C quartz substrate by using molecular beam vapor deposition method. The influence of 0 T and 6 T magnetic fields on the structural evolution and magnetic properties of thin films was studied by using EDXS, XRD, AFM and VSM. In this study, only α phase was formed in both thin films. It was found that the application of a 6 T magnetic field obviously decreases the RMS of surface roughness and the grain size. For the magnetic properties of the thin films, the 6… More >

L.B. Borkowski¹, K.C. Liu¹, A. Chattopadhyay¹

CMC-Computers, Materials & Continua, Vol.37, No.3, pp. 161-193, 2013, DOI:10.3970/cmc.2013.037.161

Abstract The microstructural variation in fiber-reinforced composites has a direct relationship with its local and global mechanical performance. When micromechanical modeling techniques for unidirectional composites assume a uniform and periodic arrangement of fibers, the bounds and validity of this assumption must be quantified. The goal of this research is to quantify the influence of microstructural randomness on effective homogeneous response and local inelastic behavior. The results indicate that microstructural progression from ordered to disordered decreases the tensile modulus by 5%, increases the shear modulus by 10%, and substantially increases the magnitude of local inelastic fields. The experimental and numerical analyses presented… More >