International Journal of Computational Materials Science and Engineering

This work presents experimental and computational studies on progressive failure analysis of notched cross-ply carbon fiber reinforced polymer (CFRP) composite. The carbon/epoxy composite laminated with [90/0]_s layup is tested using double-notched specimens loaded in tension. The load-displacement curve, failure load and damage patterns of all tested specimens are discussed. In addition, a numerical analysis approach based on material property degradation method (MPDM) and cohesive elements (CE) is illustrated to capture complex failure mechanisms and damage progression as observed in the tested specimens. The MPDM is used to model the in-plane failure of 90° plies and 0° plies while the cohesive elements are used to account for the delamination at the [90/0] interfaces. Different progressive failure models employing fracture mechanics, continuum mechanics and micromechanics of failure are presented based on the MPDM-CE approach. The failure analyses by these progressive models are performed and their predictions are compared with the experimental results of notched [90/0]_s CFRP composite. Reasonably good agreement between experimental results and simulation results is obtained and it is shown that the MPDM-CE approach can effectively predict the progressive failure of double-notched [90/0]_s composite laminate.

This paper describes a comparative study on free vibration of bending stiff, torsion stiff and quasi-isotropic graphite-epoxy composite conical shells with single and multiple delamination. The finite element formulation is based on Mindlin's theory and multi-point constraint algorithm neglecting the Coriolis effect for moderate rotational speeds. Computer codes are developed employing QR iteration method to obtain delaminated natural frequencies under combined effect of twist and rotation. Mode shapes are depicted for a typical laminate configuration. The non-dimensional natural frequencies obtained are the first known results which could serve as reference solutions for future investigators.

In this article, micro and nano titania (TiO₂) filled A384 alloy composites are fabricated by stir casting technique with varying filler content from 0–8 wt.% respectively and then we study their physical, mechanical, thermal and erosive wear characteristics respectively. Effect of impact velocity (25–70 m/sec) and impingement angle (30°–90°) on erosion wear behavior of micro and nano TiO₂ filled A384 alloy has also been studied. Finally, an optimization technique was implemented in order to develop a correlation between the physical, mechanical and erosion rate of TiO₂ filled A384 alloy composites by using technique order preference by similarity to ideal solution (TOPSIS).

By this work, we aim to study the dynamical and the thermodynamic properties of the zinc-blende GaX (X = N, P, As and Sb) using the Ab initio simulation method. Indeed, we studied the lattice dynamics, the constant-volume specific heat (Cv), the internal energy (U), the entropy (S) and the free energy (F). The observed differences between the properties of GaX elements were discussed. Our results and the available literature data (theoretical and experimental) seems to be in good agreement. Moreover, Cv, U, F and S were calculated by using the harmonic approximation in the calculation of the dynamic lattice vibration. The good agreement between our results of both the phonon frequency, the constant-volume specific heat and the experimental data allows us to conclude that our results of S, U and F of GaX were well predicted.

The thermoelectric power (S) of K₃C₆₀ fullerides is theoretically analyzed. Mott expression within parabolic band approximation is used to reveal the electron diffusive thermoelectric power (S_c^diff) following Fermi energy as electron parameter, S_c^diff show linear temperature dependence. S infers a change in slope above transition temperature and become almost linear above 70 K. The phonon drag thermoelectric power (S_ph^drag) is computed within relaxation time approximation when thermoelectric power is limited by scattering of phonons from defects, grain boundaries, phonons and electrons as carriers. The S_ph^drag of K₃C₆₀ is anomalous and it is an artifact of strong phonon-electron and phonon scattering mechanism. The thermoelectric power within relaxation time approximation has been taken into account ignoring a possible energy dependence of the scattering rates. Behaviour of S(T) is determined by competition among the several operating scattering mechanisms for the heat carriers and a balance between carrier diffusion and phonon drag contributions.

In this paper, a Finite Element (FE) framework for studying diffusion induced mechanics of Li-ion battery electrode materials is presented. In a previous study [Vanimisetti and Ramakrishnan (2011), Proc. IMechE, Part C: J. Mech. Eng. Sci. 0954406211432668], a set of analytical expressions for the stress distribution in ideal geometries, such as slab and cylindrical shaped particles, were derived using thermal stress analogy while solutions for spherical particles already exist. However, the limitations of the analytical study in handling complex geometries, the material behavior and the functional parameters necessitated the development of an FE model based approach. A multi-physics model was developed in COMSOL^® package linking diffusion phenomenon to stress development. The model was verified comparing the results with those of the earlier analytical studies. As an illustration, we use the model to make inferences with regard to the effect of electrode particle shape. Along similar lines, the diffusion-induced mechanics in silicon rod structures grown on copper current collector is also demonstrated.

In this paper, a multiscale modeling framework has been established between peridynamics and atomistic models. Peridynamics (PD) formulation is based on continuum theory implying nonlocal force based interactions. Peridynamics (PD) and molecular dynamics (MD) have similarities since both use nonlocal force based interaction. It means continuum points in PD and MD atoms are separated by finite distance and exert force upon each other. In this work PD based continuum model of epoxy polymer is defined by meshless Lagrangian particles. MD is coupled with PD based continuum model through a hierarchical multiscale modeling framework. In this framework, PD particles at coarse scale interact with fine scale PD particles by transferring pressure, displacements and velocities among each other. Based on the same hierarchical coupling method, fine scale PD model is seamlessly interfaced with molecular model through an intermediate mesoscale region i.e. coarse-grain atomic model. At the end of this hierarchical downscaling, the information — such as deformation, energy and other important parameters — were captured in the atomistic region under the applied force at micro and macro regions. A two-dimensional plate of neat epoxy was considered for demonstration of such multiscale simulation platform. The region of interest in the 2D plate was interfaced with atomistic model by applying the proposed hierarchical coupling method. The results show reasonable consistency between PD and MD simulations.

Graphene is a promising candidate as a material used in nano-scale devices because of recent developments in advanced experimental techniques. Motivated by recent successful fabrications of U-shaped graphene channel transistors by using the gallium focused ion beam technology, we have performed ab-initio calculations to investigate the electronic properties and quantum transport in U-shaped graphene nanoribbons. The electronic properties are calculated using a numerical atomic orbital basis set in the framework of the density functional theory. The transport properties are investigated using the non-equilibrium Green's function method. The transmission spectra of U-shaped graphenes are analyzed in order to reveal the quantum transport of the systems. We found that the graphene nanoribbons tend to open a band gap when U-shaped structures are formed in both armchair and zigzag cases. The geometrical structures of U-shaped GNRs had enormous influences on the electron transport around the Fermi energy due to the formation of quasi-bound states at zigzag edges. The obtained results have provided valuable information for designing potential nano-scale devices based on graphenes.