Existence and uniqueness results for well-posed laminated composite shell models

Recently, several power plants from the rotation of turbine with tidal current have been tried. Since the density of seawater is 800 times as much as that of the air, the loading of water on a turbine strictly requires much more strength and stiffness of blade compared with the wind turbine. Neither wind turbine nor standard hydroelectric dam turbines can simply be submerged into an ocean current. There are some formidable technical challenges to be overcome compared with the wind turbine. Key issues are cost effectiveness, structural integrity and workability in access and installation. The metal blade has enough strength, but is too heavy to install and handle easily. The light weight and extreme strength are essential to the blade. The objective of this work is to determine the mechanical properties of the tidal turbine, and to examine the availability of the turbine blade of composite materials for an approach to eliminate the above problems. The study was conducted in the preliminary study of the demonstration plant, which will be settled in Oma Promontory, Aomori Prefecture in Japan, whose maximum power output is 300kW and turbine diameter is 11 meters. A number of materials were considered, i.e. comprised rolled steel, aluminum bronze, GFRP for blade. We made two models for structural study based on the propeller blade shape with thin section and the wind turbine blade shape with thick section. The FEM analysis were conducted as follows, Aluminum-Bronze solid model with propeller shape; the real model at the present moment in the Oma plant. Composite material solid model; same shape as propeller but applied with composite materials. Composite material shell model with wind turbine blade Shape; structured by monocoque construction with changing the thickness by 10mm from 10mm to 50mm. The properties of GFRP for the structural study were measured from the ISO-laminates, which were fabricated by VaRTM, of multi-axial non-crimp fabrics and epoxy. Furthermore, the vibratory cavitation erosion tests of Composite materials were conducted. In order to compare with the aluminum bronze and composite, each cavitations weight loss in fresh-water were measured and observed. As the result, the multi-axial GFRP for propeller type blade was insufficient in rigidity and strength of shear. It is necessary to use not GFRP but CFRP for the propeller type blade. In contrast, as for wind turbine type blade, it was led to the conclusion GFRP blade is workable. As for erosion, the durability of composite materials is remarkably inferior to metals.

A presentation is made of the numerical results obtained in a stress–strain analysis of thin and nonthin orthotropic shells with due regard for the physical nonlinearity and small and nonsmall shear stiffness of composites. A spherical shell with a circular hole is used as an example to analyze how the above-mentioned factors affect the distribution of stresses and strains depending on the shell thickness for adopted deformation models (the Kirchhoff–Love and Timoshenko hypotheses). Generalized conclusions are drawn from which it is possible to decide which of the composite properties and shell models should be given more priority.

The buckling behaviour of thin-walled composite cylindrical shells with different rib profiles under hydrostatic pressure is studied in this paper. Various models of composite shells with outer diameter of 324 mm, thickness of 8 mm, length of 800 mm, and 18 different rib profiles are designed. Ribs have same sectional area and the total height is no more than 18 mm. Finite element (FE) models are built and validated by published experimental and FE results. The results for above models are obtained and show that the critical buckling pressure of ring-stiffened composite shells can improve by 44% to 136% compared to that of unstiffened composite shells. The rib total height, web thickness, and rib profile type are three factors affecting the critical buckling pressure of ring-stiffened composite shells. The composite shell stiffened by groove shape can acquire maximum buckling-carrying capacity.

The present work investigates Multi – channel Active Vibration Control (AVC) of a composite research wing model and shell structure using modified Filtered × Least Mean Square (F×LMS) algorithm on Field Programmable Gate Arrays (FPGAs). AVC, using Digital Signal Processing (DSP) techniques are cost effective. But FPGAs, consuming small silicon area, have emerged as a dominant technology in embedded applications with potential features like high speed processing and low power consumption. Prominent features like high-speed parallel processing architecture along with hardware reconfigurability facilitates its usage to be wide spread in signal processing applications. An adaptive active vibration control system based on feed forward modified F×LMS algorithm implemented on FPGA hardware is presented here. The results from the Multi channel real time AV C studies are brought out in the paper.

A model for the numerical analysis of masonry subjected to out-of-plane loading is proposed. The proposed composite plasticity model is able to reproduce elastic and inelastic behavior in two orthogonal directions coinciding with the orientation of the bed and head joints of masonry. The implementation of the model is described, and a comparison with experimental data on masonry strength is provided. Good agreement is found for different masonry types. Further validation of the model with experimental results on masonry panels subjected to out-of-plane loading demonstrates the accuracy of the proposed approach and the possibilities offered by numerical analysis for the understanding of the complex nonlinear phenomena involved in the failure of masonry plates and shells. In particular, this paper addresses issues such as the adequacy of yield-line analysis for the design of masonry structures subjected to out-of-plane loading, the influence of the aspect ratio of the panels, and the influence of in-plane normal pressure.

Active control of doubly curved laminated composite shells using elliptical smart constrained layer damping treatment

In this study, a laminated composite shell with uniformly applied hydrostatic pressure on its external surface is investigated numerically and experimentally. A numerical buckling analysis is carried out on a laminated composite shell with various nonlinearities including geometrical nonlinearity, material nonlinearity and geometric imperfection to obtain the critical buckling pressure using the commercially available software ANSYSⓇ. The eigen mode shape imperfection in the geometry is considered for the nonlinear buckling analysis of composite shell. The force-induced inward dimple (FID) and eigen affine imperfections are also considered for the numerical analysis. The nonlinear governing differential equations of the buckling performance of the shell are solved using the arc-length method coupled with nonlinear finite element analysis. The developed nonlinear finite element modeling of the composite shell is validated by comparing the critical buckling pressures available in the literature obtained for the composite cylinder and prolate and oblate composite domes. Further, the effectiveness of the developed numerical modeling and analysis is demonstrated by performing an experimental investigation on a prototype shell made up of GFRP composites and subjected to external hydrostatic pressure. Various parametric studies are also performed to study the effect of aspect ratio of the shell and ply configuration of the composite shell. It was shown that the buckling pressure of the composite shell is decreased if the FIDs are located at the apex of the shell and eigen affine imperfection amplitude of the shell is increased. However, a substantial effect in the critical pressure of the composite shell could not be observed, if the position of FIDs is located towards the bottom of the shell. It is also found that the composite shell with all 90° ply orientation having aspect ratio of 0.5 yields higher critical buckling pressure.

A dynamic micromechanical model based on the asymptotic homogenization pertaining to smart composite and reinforced shells with piezoelectric and piezomagnetic constituents is developed in this paper. Central to the work is the recovery of the so‐called unit cell problems which allow the calculation of the effective coefficients. In turn, these are substituted into the governing equations to obtain a set of basic macroscopic variables which eventually yield asymptotic expansions of all field variables (mechanical stress, electric and magnetic displacement, heat flux etc.). Highlights of the presented dynamic model include the following: (1) the effective properties of the homogenized structure depend strongly on the curvature of the middle surface of the shell; (2) the effective properties are also temporal functions and not merely spatial ones as predicted by other models; (3) the effective properties reflect the influence of all involved constituent material parameters; and (4) the model captures not only the common product properties (magnetoelectricity, pyroelectricity, pyromagnetism) but also other ones relating current density to mechanical displacement, magnetic field, and temperature. These features essentially mean that the homogenized shell is characterized by inhomogeneity or quasi‐homogeneity after the homogenization process and also exhibits memory effect reminiscent of viscoelastic structures. If electrical conductivity is ignored and the effective properties are averaged over the entire time spectrum the results of the model converge to those of previously published quasi‐static models. If, as well, the electrical and magnetic effects are also suppressed the results of the model converge to those of the classical composite shell model.

Amplitude non-linearity of the electrically evoked compound action potential (eCAP) of the auditory nerve

Parametric instability of delaminated composite curved panels subjected to moist environment

This article investigates the influence of finite element model features on Fiber Reinforced Polymer (FRP) crushing simulation results. The study focuses on two composite material tube models using single shell modeling approach. The chosen material model is MAT58 (*MAT_LAMINATED_COMPOSITE_FABRIC) from the commercial finite element analysis software LS-Dyna. The baseline models geometry and material parameters come from a model calibration conducted for lightweight vehicle investigation. Five parameters are investigated. The mesh size and the number of integration point (NIP) are generic and ERODS, TSIZE and SOFT are the non-physical parameters of MAT58. This analysis aims at discuss the influence of these parameters on the simulation results focusing on the initial force peak and the average crush load, regarding results realism and instabilities such as large elements deformation and abnormal peak values. Also, the impact of the number of CPUs involved in the simulation calculation is presented. Recommendations are given to set the mesh size and the NIP. TSIZE value should be selected regarding the simulation time step. On the other hand, ERODS has to be adjusted manually. Both are determinant for simulation robustness. Further studies are proposed to find out the reasons of large element deformation.

In this paper free linear vibration of lattice composite conical shells will be investigated. Lattice composite conical shell consists of composite helical ribs and thin outer skin. A smeared method is employed to obtain the variable coefficients of stiffness of conical shell. The ribs are modeled as a beam and in addition to the axial loads, endure shear loads and bending moments. Therefore, theoretical formulations are based on first-order shear deformation theory of shell. For verification of the obtained results, comparison is made with those available in open literature. Also, using FEM software the 3D finite element model of composite lattice conical shell is built and analyzed. Comparing results of analytical and numerical analyses show a good agreement between them. Some special cases as variation of geometric parameters of lattice part, effect of the boundary conditions and influence of the circumferential wave numbers on the natural frequencies of the conical shell are studied. It is concluded, when mass and the geometrical ratio of the composite lattice conical shell do not change, increment the semi vertex angle of cone leads to increase the natural frequencies. Moreover for shell thicknesses greater than a specific value, the presence of the lattice structure has not significant effect on the natural frequencies. The obtained results have novelty and can be used for further and future researches.

Magneto-electro-elastic semi-analytical models for free vibration and transient dynamic responses of composite cylindrical shell structures

Pipelines for deep-water application should be designed to be extremely flexible to ease the installation procedures. Such flexibility will improve the bending instabilities of reeled pipelines during spooling of initially straight or laying of initially bent pipe. Also during construction, pipeline flexibility could be exploited to connect pipelines and risers to floaters, manifolds, wellheads, buoys, and platforms. Therefore, the proposed flexible pipe is designed to be positionable and bendable enough to fit the above requirements. The pipe is comprises a series of interconnected ball-and-socket sections forming a liner and a fluid-tight cover, one or more helical wounding layers applied to the internal liner for absorbing tension loads, and one or more additional helical wounding layers applied for absorbing bending loads. In order to form a liner, the ball-and-socket segment will passes through a die, while a thread guide applies a plurality of reinforcing threads in a particular pattern to the exterior surface thereof to keep the segments to be snappingly engageable and maintain the pipe flexibility without significantly increasing in the thickness of the pipe wall or weight. The ball and socket segments are assumed manufactured from a lightweight composite material consisting of epoxied matrix reinforced by long continuous fibers. The socket segment was assumed a stiffer ring. Therefore, this paper will emphases on the design parameters of the ball joint that form the pipe by modeling it as laminated composite barrel shell and examining its elastic deformations capacity under pure bending conditions (e.g., typical reeling installation condition). To this aim, a straightforward treatment of the problem is presented via using Hamilton's principle and based on the first order shear deformation theories. The solution of the laminated composite barrel shell was formulated to follow exactly a simply supported boundary condition. Finally, the in-plane stresses and inter-laminar stresses were evaluated for wide range of loading conditions. Introduction The so called; a flexible ball socket joint, thread flexible round, or ball joint pipe is anticipated to be used in particular, although not exclusive, as utility in offshore or onshore for the transportation of petroleum oil and gas or other fluids. Such pipes are made up of a number of substantially rigid composite ball and socket segments, each segment combine the low weight and high strength properties. Thereby the pipe becomes extremely bendable and sufficiently flexible to spool onto reel for the purpose of reeling installation. Although flexible pipes are well known in the art and are for example they described in the standards; ANSI/API 17 B; Recommended Practice for Flexible Pipe, and ANSI/API 17J; Specification for Unbonded Flexible Pipe, the ball joint pipes haven't modeled yet. In this paper the proposed flexible ball socket joint pipe was invented to fulfill a number of requirements:First of all the pipe was designed to have a very high mechanical strength to withstand the forces it will be subjected to during transportation, deploying and in operation.The ball segments was designed to withstand the internal pressure that are usually considered very high and may vary considerably along the length of the pipe, in particular when applied at varying water depths. Therefore, the ball segments will be stiffer enough to resist the different in pressure, result in preventing the pipeline damage such as burst and collapse.The flexible pipe was designed from specific composite materials to be highly non-corrosive and chemical resistance.The proposed ball joint pipe was designed to keep the weight of the pipe relatively low, both in order to reduce transportation cost and deployment cost but also in order to reduce risk of damaging the pipe during deployment.

A closed-form 3D shell solution for multilayered structures subjected to different load combinations