7 research outputs found

    Transient thermal conduction in rectangular fiber reinforced composite laminates

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    A finite element formulation based on the Fourier law of heat conduction is presented to analyze the transient temperature distribution in rectangular fiber-reinforced composite plates. Three-dimensional twenty-noded brick elements are used to discretize the spatial domain of the plate. A Crank-Nicolson time marching scheme is used to solve the resulting time-dependent ordinary differential equations. The finite element solution is tested for convergence of results with mesh refinement. Further, the FEM is validated comparing the qualitative nature of results obtained for a plate made of aluminium and steel laminae with that of Tanigawa et al. Results are presented for graphite/epoxy and graphite-kevlar/epoxy plates subjected to different thermal boundary conditions. Laminae with fiber orientations of 0amp;deg;, amp;plusmn45amp;deg;, and 90amp;deg; are considered for the analysis. The results indicate that the temperature variation in the plane of the plate (x-y plane) is very much dependent on the boundary conditions. When the faces of the plate through the thickness are insulated, the number of elements in the x-y plane is observed to have no effect on the accuracy of the result

    Best-fit stress performance of a higher-order beam element13;

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    It is known that finite elements try to capture stresses within each discretized local region in a 'best-fit' sense. In the paper we examine the performance of a beam element based on a higher-order shear deformation theory and show that the best-fit paradigm accounts for the manner in which through-the-thickness displacement and stresses are modelled. An a priori prediction derived from the paradigm is confirmed by a carefully chosen numerical experiment. This provides a measure of the quality of approximation as well as another 'falsification' of the best-fit paradigm

    Best Fit stress Performance of a High order beam element

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    It is known that finite elements try to capture stresses within each discretized local region in a 'best-fit' sense. In the paper we examine the performance of a beam element based on a higher-order shear deformation theory and show that the best-fit paradigm accounts for the manner in which through-thethickness displacement and stresses are modelled. An a priori prediction derived from the paradigm is confirmed by a carefully chosen numerical experiment. This provides a measure of the quality of approximation as well as another 'falsification' of the best-fit paradigm

    Beam elements based on a higher order theory-II - Boundary layer sensitivity and stress oscillations

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    The flexure of deep beams and thick plates and shear flexible (e.g. laminated composite) beams and plates is often approached through a finite element formulation based on the Lo-Christensen-Wu (LCW) theory. A systematic analytical evaluation of beam elements based on the LCW higher order theory was carried out recently. It turns out that the availability of a large number of degrees of freedom to prescribe end/boundary conditions leads to discontinuity effects that trigger off wiggles (sharp13; oscillations) in some of the higher order displacement terms. These wiggles propagate outward from the point of excitation and disturb the transverse normal stress predictions. This paper examines the origin of these oscillations and how these boundary layer effects can be contained by refined modeling within the boundary layer zone or region when beam elements based on this higher order theory are used. A similar difficulty should be present in plate elements based on the same theory

    Beam elements based on a higher order theory-I: Formulation and analysis of performance

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    The flexure of deep beams, thick plates and shear flexible (e.g. laminated composite) beams and plates is often approached through a finite element formulation, based on the Lo-Christensen-Wu (LCW) theory. This paper is a systematic analytical evaluation of the use of the LCW higher order theory for finite element formulation. The accuracy and other features of the computational model are evaluated by comparing finite element method (FEM) results with available closed form classical and elasticity solutions. Wherever possible, errors are predicted by an a priori analysis using these solutions and concepts from an understanding of what the finite element method does
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