Thermoelastic Problems of Multilayered Cylinders

Thermoelastic problems of long multilayered cylinders manufactured from isotropic materials are considered. The steady-state thermal field corresponding to a constant difference between temperature outside and inside the assembly is used in the analysis. Both the case of a hollow cylinder and that of a solid multilayered assembly are discussed. A closed-form exact solution is shown for an arbitrary number of layers if the properties of constituent materials remain unaffected by temperature. Various strategies leading to an analytical solution are proposed for the case where material properties depend on temperature. The stresses in a dual-coated optical fiber subject to a uniform temperature are determined as a particular cas

Thermoelastic Problems of Multilayered Cylinders

Thermoelastic problems of long multilayered cylinders manufactured from isotropic materials are considered. The steady-state thermal field corresponding to a constant difference between temperature outside and inside the assembly is used in the analysis. Both the case of a hollow cylinder and that of a solid multilayered assembly are discussed. A closed-form exact solution is shown for an arbitrary number of layers if the properties of constituent materials remain unaffected by temperature. Various strategies leading to an analytical solution are proposed for the case where material properties depend on temperature. The stresses in a dual-coated optical fiber subject to a uniform temperature are determined as a particular cas

Extension Of Vlasov’s Semi-membrane Theory To Reinforced Composite Shells

Governing equations for the statics and dynamics of reinforced composite shells are developed based on Vlasov\u27s semi-membrane shell theory. These equations have closed-form solutions illustrated for buckling and free vibration problems. The buckling solution converges to the known result for unstiffened isotropic shells. © 1992 by ASME

Thermal Dynamic Problems Of Reinforced Composite Cylinders

Thermal dynamic problems of circular cylindrical composite shells reinforced in the axial and circumferential directions and subject to variations of temperature are considered. Nonlinear governing equations are formulated based on the extension of Donnell shell theory. These equations are used to determine the response of geometrically nonlinear and linear shells to a thermal loading represented by the Heaviside step function (thermal shock). The solution of the nonlinear problem obtained by the assumption that displacements are single-term functions of coordinates is discussed. The analysis of the linear problem illustrates different types of response to thermal shock. The condition of thermally induced buckling of shells is formulated. Numerical analysis results in conclusions regarding the behavior of shells subject to thermal shock if the temperature is uniformly distributed throughout the shell and stiffeners. © 1990 by ASME

Wrinkling of Composite-facing Sandwich Panels Under Biaxial Loading

The problem of face wrinkling in sandwich structures was identified as an important failure mode and first analyzed in 1940 by Gough et al. [1], who used a Winkler-type elastic foundation to model the core. This work was followed by experiments and further analysis by many others. Until 1966 all of the research was devoted to uniaxial compression loading. However, in many applications, such as naval and aircraft structures, panels are subjected to biaxial loading. Such loadings were first analyzed by Plantema in 1966 [2] for the case of sandwich constructed of isotropic materials. Sullins et al. [3] suggested an interaction equation that can be used as a criterion of wrinkling under compression in the principal directions. This equation is formulated in terms of the ratios of the principal compressive stresses to the corresponding wrinkling stresses. More recently Fagerberg [4, 5] and Vonach and Rammerstorfer [6] considered the case of sandwich with orthotropic facings.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

Micromechanics of composites with shape memory alloy fibers in uniform thermal fields

Analytical procedures are developed for a composite system consisting of shape memory alloy fibers within an elastic matrix subject to uniform temperature fluctuations. Micromechanics for the calculation of the equivalent properties of the composite are presented by extending the multi-cell model to incorporate shape memory alloy fibers. A three phase concentric cylinder model is developed for the analysis of local stresses which includes the fiber, the matrix, and the surrounding homogenized composite. The solution addresses the complexities induced by the nonlinear dependence of the in-situ martensite fraction of the fibers to the local stresses and temperature, and the local stresses developed from interactions between the fibers and matrix during the martensitic and reverse phase transformations. Results are presented for a nitinol/epoxy composite. The applications illustrate the response of the composite in isothermal longitudinal loading and unloading, and in temperature induced actuation. The local stresses developed in the composite under various stages of the martensitic and reverse phase transformation are also shown

Multiphase elastic homogenization, and the mechanics of tendon-to-bone attachment

Estimates of the effective stiffness of a composite containing multiple types of inclusions are needed for the design and study of functionally graded systems in engineering and biologic materials. One important stiffening mechanism in biologic systems is the accumulation of a high volume fraction of mineral inclusions within and upon collagen fibers. Modeling of this mechanism is critical for understanding how stresses are transmitted from tendon to bone and for designing improvements to surgical procedures for reattaching tendon to bone. The latter is a critical need because failure rates following surgical reattachment are as high as 94% in some populations. Modeling of such material remains difficult Because of a number of physiological and mathematical challenges. A range of methods have been described in the literature for estimating the effective elastic properties of composites containing low volume fractions of different inclusion types. Here, we provide an estimate of the effective elastic responses of composites containing high volume fractions of different, ellipsoidal and anisotropic inclusion types. The homogenization estimate compared well against numerical simulation and available experimental data. The method out-performed all methods of which we are aware for modeling of numerical simulations of the mechanical response of the graded attachment of tendon to bone. The method is a good candidate for the characterization of composites with multiple types of anisotropic inclusions, even if these inclusions have moderate volume fractions and a variety of aspect ratios

Detection of Delaminations in Composite Beams Using Piezoelectric Sensors

This paper investigates the feasibility of a proposed technique for detecting delamination using piezoelectric layers or patches embedded or bonded to a composite structure. Variations in the voltage generated in the piezoelectric layers indicates the presence and location of delamination, when the structure is excited either externally or via actuators. The theoretical foundations of a method for predicting the dynamic response of delaminated composite beams with piezoelectric layers are described. The governing equations are presented for the case of external vibroacoustic excitation, as well as, for the case of locally induced vibrations by some of the embedded piezoelectric elements. An exact solution is developed within the limits of linear laminate theory. Applications illustrate the feasibility of delamination detection in cantilever beams. The results illustrate that the proposed technique may provide accurate detection of the presence, size, and location of a delamination

Functionally Graded Stitched Laminates: Illustration on the Example of a Double Cantilever Beam

Abstract: Although stitched laminates have been shown effective in preventing delamination failure, the presence of stitches results in a degraded in-plane strength and stiffness in such structures. The solution suggested in the paper is based on using stitches only in a part of the structure where they serve as arrestors of delamination cracks, while the part subject to considerable in-plane loading could remain unstitched. This approach, that could be called "functionally graded stitching," is considered on the example of a double cantilever beam ͑DCB͒ with a preexisting delamination crack that has penetrated into the stitched region of the beam. As is shown in the paper, the distribution of stitches in a functionally graded DCB ͑and in any other laminated structure͒ should be chosen to prevent three major failure modes. These modes include the failure of the stitches, bending failure of the unstitched delaminated section of the structure, and continuous crack propagation through the stitched region. The results obtained in the paper for the static problem clearly illustrate the feasibility of using functionally graded stitched laminates retaining in-plane strength and stiffness, while providing barriers to delamination cracks in less loaded regions of the structure. Additionally, the approach to the solution of the dynamic problem presented in the paper may be applied to the analysis of fatigue delamination cracks in partially stitched structures