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  • Open Access

    ARTICLE

    A Multiscale Progressive Failure Modeling Methodology for Composites That Includes Fiber Strength Stochastics

    Trenton M. Ricks1, Thomas E. Lacy, Jr.1,2, Brett A. Bednarcyk3, Steven M.Arnold3, John W. Hutchins1

    CMC-Computers, Materials & Continua, Vol.40, No.2, pp. 99-130, 2014, DOI:10.3970/cmc.2014.040.099

    Abstract A multiscale modeling methodology was developed for continuous fiber composites that incorporates a statistical distribution of fiber strengths into coupled multiscale micromechanics/ finite element (FE) analyses. A modified twoparameter Weibull cumulative distribution function, which accounts for the effect of fiber length on the probability of failure, was used to characterize the statistical distribution of fiber strengths. A parametric study using the NASA Micromechanics Analysis Code with the Generalized Method of Cells (MAC/GMC) was performed to assess the effect of variable fiber strengths on local composite failure within a repeating unit cell (RUC) and subsequent global failure. The NASA code FEAMAC… More >

  • Open Access

    ARTICLE

    On the Homogenization Analysis of Electromagnetic Properties for Irregular Honeycombs

    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 >

  • Open Access

    ARTICLE

    A Simple Locking-Alleviated 4-Node Mixed-Collocation Finite Element with Over-Integration, for Homogeneous or Functionally-Graded or Thick-Section Laminated Composite Beams

    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 >

  • Open Access

    ARTICLE

    Localization in Time of Solutions for Thermoelastic Micropolar Materials with Voids

    Marin Marin1, Ravi P. Agarwal2, Mohamed Othman3

    CMC-Computers, Materials & Continua, Vol.40, No.1, pp. 35-48, 2014, DOI:10.3970/cmc.2014.040.035

    Abstract In this study we want to decide whether the decay of the solutions of the mixed initial boundary value problem in the context of thermoelasticiy of micropolar bodies with voids is sufficiently fast to guarantee that they vanish after a finite time. In fact, we prove that the effect of the micropolar structure in combination with the thermal and porous dissipation can not determine the thermomechanical deformations vanish after a finite time. More >

  • Open Access

    ARTICLE

    Nonlinear Symmetric Free Vibration Analysis of Super Elliptical Isotropic Thin Plates

    Da-Guang Zhang1,*, Hao-Miao Zhou1

    CMC-Computers, Materials & Continua, Vol.40, No.1, pp. 21-34, 2014, DOI:10.3970/cmc.2014.040.021

    Abstract Nonlinear symmetric free vibration analyses are first presented for super elliptical isotropic thin plates with simply supported edge and clamped edge based on classical plate theory. Approximate solutions of super elliptical thin plates are obtained by Ritz method, and the validity can be confirmed by comparison with related researchers’ results. Numerical results confirm that the characteristics of nonlinear vibration behaviors are significantly influenced by different boundary conditions, vibration amplitudes, the power of the super ellipse, as well as ratio of major to minor axis. More >

  • Open Access

    ARTICLE

    A Real-time Monitoring Technique for Local Plasticity in Metals Based on Lamb Waves and a Directional Actuator/Sensor Set

    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 >

  • Open Access

    ARTICLE

    Characteristics of a Single I-shaped Slitted Zeroth-Order Resonance Mushroom Antenna based on Metamaterials

    Cherl-Hee Lee, Jonghun Lee1

    CMC-Computers, Materials & Continua, Vol.39, No.3, pp. 289-299, 2014, DOI:10.3970/cmc.2014.039.289

    Abstract The broadband design of a metamaterials-based zeroth-order resonance (ZOR) mushroom antenna with an I-shaped slit is presented and experimentally studied. The presented metamaterials-based antenna uses a unit cell based on a composite right/left handed (CRLH) transmission line and can provide a ZOR frequency. By designing the I-shaped slot resonance frequency adjacently to the ZOR frequency, the presented antenna can achieve a 10-dB bandwidth enhancement of roughly 7 times with respect to a conventional rectangular-shaped mushroom structure. More >

  • Open Access

    ARTICLE

    Some Applications of Metamaterial Resonators Based on Symmetry Properties

    J. Naqui1, F. Martín1

    CMC-Computers, Materials & Continua, Vol.39, No.3, pp. 267-288, 2014, DOI:10.3970/cmc.2014.039.267

    Abstract Metamaterial resonators are electrically small resonant particles useful for the implementation of effective media metamaterials. In this paper, some applications of metamaterial resonators (such as the split ring resonator -SRR-, the complementary split ring resonator -CSRR-, the folded stepped impedance resonator -SIR-, and the electric LC resonator), that exploit the symmetry properties of transmission lines loaded with such symmetric particles, are reviewed. This covers differential (balanced) lines with common mode suppression, linear and angular displacement sensors (including alignment sensors), angular velocity sensors, and radiofrequency barcodes. Advantages and drawbacks as compared to existing implementations are also discussed. More >

  • Open Access

    ARTICLE

    Effective Surface Susceptibility Models for Periodic Metafilms Within the Dipole Approximation Technique

    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 >

  • Open Access

    ARTICLE

    Polarization Independent Dual-band Metamaterial Based Radar Absorbing Structure (RAS) for MillimeterWave Applications

    Shiv Narayan1, Latha S.1 and R M Jha1

    CMC-Computers, Materials & Continua, Vol.39, No.3, pp. 217-230, 2014, DOI:10.3970/cmc.2014.039.217

    Abstract The EM analysis of multi-layered metamaterial based radar absorbing structure (RAS) with dual-band characteristics in millimeter wave frequency regime has been carried out in this paper using transmission line transfer matrix (TLTM) method for TE and TM polarizations. The proposed metamaterial-based RAS exhibits dual-band characteristics at centre frequencies 120 GHz and 175 GHz with very low power reflection. It absorbs more than 90% power of incidence wave over the frequency range from 111-131 GHz at first resonance and from 164.5-185 GHz at second resonance without metal backing plate, which is desirable for stealth applications. It also showed very low (<… More >

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