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In this paper, we analyze an orthotropic, layered (0°/90°) and (0°/core/0°) sandwich cylinders under pressurized load with a diaphragm supported boundary conditions which is considered as a two dimensional (2D) plane strain boundary value problem of elasticity in (r, z) direction. A simplified numerical cum analytical approach is used for the analysis. Boundary conditions are satisfied exactly by using an analytical expression in longitudinal (z) direction in terms of Fourier series expansion. Resulting first order simultaneous ordinary differential equations (ODEs) with boundary conditions prescribed at r = r_i, r_o defines a two point boundary value problem (BVP), whose equations are integrated in radial direction through an effective numerical integration technique by first transforming the BVP into a set of initial value problems (IVPs). Numerical solutions are first validated for their accuracy with 1D solution of an infinitely long cylinder. Stresses and displacements in cylinders of finite lengths having various l/R and h/R ratios are presented for future reference.

A refined higher order shear deformation theory for linear and geometrically nonlinear behavior of fiber-reinforced angle-ply composite and sandwich laminates is established. Laminae material is assumed to be linearly elastic, homogeneous and isotropic/orthotropic. The theory accounts for nonlinear quadratic variation of transverse shear strains through the thickness of the laminate and higher order terms in Green's strain vector in the sense of von Karman. A simple [C.sup.0] finite-element formulation of this theory is then presented with a total Lagrangian approach, and a nine node Lagrangian quadrilateral element is chosen with nine degrees of freedom per node. Numerical results are presented for linear and geometrically nonlinear analyses of multilayer angle-ply composite and sandwich laminates. The theory is shown to predict displacements and stresses more accurately than first-order shear deformation theory. The results are compared with available closed-form and numerical solutions of plate theories and three-dimensional finite-element solutions. New results are also generated for future evaluations.

A higher order displacement based formulation has been developed to investigate wave propagation in fiber-reinforced polymer composite laminated (FRPCL) plates. The formulation has been applied, as an illustration, to a plate made up of transversely isotropic laminae with the axes of symmetry lying in the plane of the lamina. Results for the plane as well as the antiplane strain cases are shown to be in excellent agreement with the exact solutions for isotropic and transversely isotropic single layered plates. Also, numerical results have been obtained for crossply (0 deg/90 deg/0 deg/90 deg) laminated composite plates, which agree very well with the previously published numerical results. The formulation can be employed to expeditiously investigate the dispersion characteristics of waves propagating in a plate with an arbitrary number of anisotropic laminae. [DOI: 10.1115/1.1352062]

A higher order displacement model based on a cubic axial strain, cubic transverse shear strain and quadratic transverse normal strain across the thickness of the beam, to model exactly the warping of the cross section is proposed which maintains zero stress at the top and bottom of the beam with out the aid of any shear correction factor. Numerical experiments carried out clearly bring out the efficacy of this model over the first order theory for laminated beams.

Some of the results of a study conducted by S.F. Muller de Almedia and J.S. Hansen on customizing manufacturing-introduced thermal residual stress to improve the buckling strength of laminated composite plates invite comment. De Almedia and Hansen should have realized that increases in normalized buckling load should not be as much in laminates supporting higher levels of thicknesses. The thickness effect on the buckling load during the presence of thermal residual stress was re-examined.

Some of the results of J.G. Papastravridis' study on time-integral variational principles for nonholonomic systems invite comment. The principles were efficiently supported by a geometrical interpretation of the discrepancies in the equations of motions was carried out by the variational approach. In addition, there are a number of ways in which geometrical concepts could be utilized to establish a unified view of control.

The prediction of the response of structures subjected to projectiles impact may often be accomplished by means of empirical or semi-empirical formulas available in the technical literature, which address mainly cases of relevance in engineering practice in terms of the observed failure modes. The paper presents an evaluation of the performance of the equations most widely used in predictions of penetration, scabbing and perforation of concrete and rock structures by comparing the predicted results with experimentally observed response and with the results of detailed numerical analyses employing the truss-like Discrete Element Method (DEM). Numerical DEM predictions were shown to be close to the experimentally determined responses of concrete plates subjected to impact throughout the range of velocities examined and were also consistent with the empirical formulas. In all cases the authors attempted to quantify the uncertainty inherent both in the predictions of empirical formulas and of the numerical analysis. [ABSTRACT FROM AUTHOR]

ABSTRACT The prediction of the response of reinforced concrete structures subjected to projectiles impact still presents open questions. These include the rate dependence of material properties, the interaction between concrete and steel reinforcement and the simulation of fracture and fragmentation. Because the appearance of discontinuities in the target structure is difficult to account using a continuum approach, the application of discrete models was developed as an appealing alternative. A version of the discrete model in which nodal masses are linked by an array of uniaxial elements, herein called discrete element method, is used in this study. This method was implemented in the system Abaqus to take advantage of its numerical and post-processing capabilities. A reinforced concrete rectangular plate subjected to impact of a projectile is examined in detail. Comparisons between experimental and numerical results are shown with the aim of validating the proposed method. [ABSTRACT FROM AUTHOR]

Certain points should be raised on the analysis done by Amir Mirmiran and Mohsen Shahawy regarding the behavior of concrete-filled fiber reinforced polymer composite tubes. The axisymmetric model is true only for circular columns with axial loads. The condition of axisymmetry may be violated if the wrapping angle of the fiber is selected indiscriminately. This model may be of little value in studying these concrete structures but the fiber wrapping technique can be an important tool in repairing damaged compression members.

Two refined higher order theories, one that neglects and the other that takes into account the effect of transverse normal deformation, are used to develop two discrete finite element models for the thermal buckling analysis of composite laminates and sandwiches. The two models, one with nine degrees of freedom per node and the other with eleven degrees of freedom, are based on a nine-node Lagrangian isoparametric element. The geometric stiffness matrices are developed by taking into consideration the effects of the higher order terms on the initial in-plane and transverse shear stresses. The accuracy of the present formulations is first evaluated by analyzing sample problems for which analytical three-dimensional solutions exist in the literature. Numerical results are presented for the first time for sandwich plates, demonstrating the importance and accuracy of the higher order theory in comparison to first-order theory. Some new results are also given for sandwich plates with angle-ply composite face sheets, showing the effects of various boundary conditions and of variations in geometric and lamina tion parameters on critical temperature. [ABSTRACT FROM AUTHOR]

A C° continuous finite element formulation of a higher order displacement theory is presented for predicting linear and non-linear transient responses of composite and sandwich plates. The geometric non-linearity is accounted for in the sense of von Kar man assumptions and the material behaviour is assumed as elasto-perfectly plastic. The elasto-perfectly plastic material behaviour is incorporated using the flow theory of plastic ity. In particular, the modified version of Hill's initial yield criterion with amsotropic pa rameters of plasticity is used. The layered approach is adopted to account for the plasticity through the thickness of the plate. The displacement model accounts for non-linear cubic variation of tangential displacement components through the thickness of the laminate and the theory requires no shear correction coefficients. In the time domain, the explicit cen tral difference integrator is used in conjunction with the special mass matrix diagonaliza tion scheme which conserves the total mass of the element and includes effects due to rotary inertia terms. The parametric effects of the time step, finite element mesh, lamina tion scheme and orthotropy on the linear and non-linear responses are investigated. Nu merical results are presented for composite and sandwich plates under various boundary conditions and loadings and these are compared with the results from other sources. Some new results are also presented for future reference. [ABSTRACT FROM PUBLISHER]

An isoparametric C° finite element formulation based on a higher order displacement model for linear and geometrically non-linear analysis (that accounts for large displacements in the sense of von Karman) of doubly curved laminated composite and sandwich shells under transverse loads is presented. The displacement model ac counts for cubic and constant variation of tangential and transverse displacement compo nents respectively through the shell thickness. The assumed displacement model elimi nates the use of shear correction coefficients. The discrete element chosen is a nine-noded quadrilateral element with nine degrees of freedom per node. The accuracy of the for mulation is then established by comparing the present results with the available analytical closed-form solutions, three-dimensional elasticity solutions and other finite element solu tions. [ABSTRACT FROM PUBLISHER]

An unified approach is presented for the pseudo-transient (static) linear, geometric, material and combined geometric and material non-linear analyses of lami nated composite shells. A nine-noded isoparametric quadrilateral finite element belonging to the Lagrangian family is used in space discretization. An explicit time marching scheme is employed for time integration of the resulting discrete ordinary differential equations with the special forms of diagonal fictitious mass and/or damping matrices. The elasto plastic material behaviour is incorporated using a flow theory of plasticity. In particular, the modified version of Hill's initial yield criterion is used in which anisotropy parameters of plasticity are introduced. The shear deformation is accounted for using an extension of Sander's shell theory, and the geometric non-linearity is considered in the sense of von Karman strains. The layered element approach is adopted for the treatment of elasto plastic behaviour through the thickness. A wide range of numerical examples are pre sented to demonstrate the validity and efficiency of the present approach. The results for combined non-linearity are also presented. The variety of results presented here is based on realistic material properties of more commonly used advanced composite materials. The results of the combined non-linear analysis should serve as reference for future in vestigations. [ABSTRACT FROM PUBLISHER]

A set of simple but efficient and accurate higher-order displacement models are used to evaluate the multiaxial stress behavior in symmetric and unsymmetric composite and sandwich laminates. These theories incorporate a more realistic non-linear variation of displacements through the beam thickness, thus eliminating the use of shear correction coefficient(s). Constitutive relations are used to evaluate inplane stresses. The computer program developed incorporates the realistic prediction of transverse stresses from equilibrium equations. The integration of the equilibrium equations is attempted through direct integration method, forward and central direct finite difference technique and a new approach called an exact curve fitting method. The versatility of the present higher-order theories is demonstrated by comparing the results with the available elasticity and other closed-form solutions for cross-ply and sandwich laminates. The results show that the exact curve fitting method gives good estimates of multiaxial stresses compared to finite difference and direct integration methods. [ABSTRACT FROM PUBLISHER]

C° finite elements based on a set of higher-order theones are projected to provide reliable predictions for interlaminar stresses in layered composite and sandwich laminates. These theoretical-cum-computational models incorporate laminate deforma tions which account for the effects of transverse shear deformation, transverse normal strain/stress and a nonlinear variation of inplane displacements with respect to the thick ness coordinate, thus eliminating the need for shear correction coefficients. The inplane stresses are evaluated via constitutive relations, while the interlaminar stresses are evalu ated by using the equilibrium equations. 16 and 9 noded Lagrangian selectively integrated isoparametric elements are used in this study. The present results, when compared with available elasticity and closed-form laminate solutions, show good agreement. New results for sandwich laminates are also presented which may serve as a benchmark for future investigations. [ABSTRACT FROM PUBLISHER]

The application of a higher-order shear deformable theory, which assumes a realistic cross-sectional deformation pattern and eliminates the use of a shear correction coefficient, is presented to evaluate the buckling loads of a symmetric, three-layered, simply supported, sandwich column when subjected to compressive edge loads. A closed form solution of the equilibrium equations is obtained by employing Von Karman strain displacement relations in the variational statement of the total potential energy and ne glecting any stretching of the middle line. The results, when compared with those obtained from Euler-Bernoulli and Timoshenko theories, show that the high shear deformability of the core significantly reduces the buckling load, highlighting the efficacy of a higher order theory. [ABSTRACT FROM PUBLISHER]

193 schoolchildren 15 years of age were grouped as non worker and smokers on the basis of their smoking habits. In all cases an X-ray examination was made of the lower incisors, and a record was made of plaque and gingival index. The resulting values were compared between non-smokers and smokers. The following conclusion could be drawn. Oral hygiene and gingival inflammation are directly correlated. Oral hygiene is worse in smokers than in non-smokers. The gingival status is worse in smokers than in non-smokers. When investigating gingival status on the same level of oral hygiene no significant difference is found between the groups. [ABSTRACT FROM AUTHOR]

A refined and an efficient protocol for in vitro clonal propagation of Commiphora wightii, a red-listed desert plant of medicinal importance, has been developed from nodal segment of mature plant. Nodal segments from new branches having 6-7 nodes were excised after discarding the initial 5-6 cm terminal portion and were surface sterilized with 2.5% NaOCl (sodium hypochlorite), (v/v). MS medium [MURASHIGE & SKOOG, 1962] with different concentrations of BAP (6-benzylaminopurine) was used alone and in combinations with IAA (indole-3-acetic acid), NAA (α-naphthalene acetic acid), Kn (kinetin) and other additives for shoot induction. Best bud break response (84.5%) was obtained on MS medium supplemented with 8.88 µM BAP, 0.57 µM IAA and additives (50 mg l-1 ascorbic acid, 25 mg l-1 citric acid and 25 mg l-1 adenine sulphate) within 2 weeks of inoculation. The micro-shoots were subcultured and maintained for further elongation on the same medium for 4 weeks. Best shoot multiplication was obtained on same medium as used for shoot initiation. Best rooting was obtained when the shoots were initially given a 24 h pulse treatment in liquid MS medium supplemented with 4.92 µM IBA (indole-3-butyric acid) and 5.71 µM IAA under dark condition, followed by transfer to semi-solid half-strength hormone-free MS medium supplemented with 2% (w/v) sucrose and 0.5% (w/v) activated charcoal. High (86.7%) percent rooting was achieved after 4-5 weeks with 3-4 multiple adventitious roots of 5-6 cm length. These in vitro raised well rooted plantlets were acclimatized in a two step manner. During in vitro hardening step, the survival was 61.5% and during ex vitro hardening step it was 100%. Hardened plants (10-12 cm in height) were transferred to polythene-bags filled with mixture of soil and FYM in the ratio of 2:1 (v/v) and were kept in 75% agro-net shade for one month, where they gained height up to 60 cm. Five month old hardened plants were planted in open field condition for evaluation of these tissue cultured raised plants. There is cent percent survival of these field grown plants over period of two years with no visible morphological abnormalities. Genetic fidelity test was carried out for these in vitro raised plants by using RAPD primers (OPA and OPN). Uniform banding pattern was observed in all plants without any polymorphism.

Presents an innovative idea of tailoring the manufacturing-introduced thermal residual stresses in order to enhance the buckling strength of laminated composite plates. Effects of the tailored thermal residual stresses; How buckling loads of reinforced plates are normalized; Thickness effect on the buckling load in the presence of thermal residual stresses.