This paper reports an experimental investigation into the effect of laundering on seam tensile properties with the variation of stitch density, linear density of sewing threads and composition of base material. Tensile properties such as initial modulus, secant modulus, seam strength, strain at fracture and work up to fracture increase with stitch and linear density of sewing threads. The impact of coarser yarn is greater on seam properties of polyester-cotton fabric than cotton fabric. The tensile properties except seam strain are reduced due to laundering. Reduction in initial modulus and secant modulus due to laundering is higher for polyester-cotton fabric whereas decrease in seam strength, seam efficiency and strain at break is greater for coarser sewing thread.
In this paper a finite element computational procedure is presented for the determination of first-ply failure strengths of pretwisted rotating plates subjected to centre point transverse load. The finite element model is based on the tensor polynomial failure criterion that contains the maximum stress, maximum strain, Tsai-Hill, Tsai-Wu and Hoffman failure criteria as special cases. A nine-noded three-dimensional degenerated composite shell element is developed and used for the present finite element formulation. Effects of transverse shear deformation and rotary inertia are included. Lagrange's equation of motion is employed to derive the dynamic equilibrium equation considering moderate rotational speeds for which the Coriolis effect is negligible. Finally, the static equilibrium equation is formulated after discarding the time-dependent terms. Failure load computations for rotating cantilever plates with nonlinear pretwist are carried out to investigate the effects of angle of twist, rotational speed and laminate configuration.
Finite element procedure is employed to analyze the free vibration characteristics of rotating functionally graded carbon nanotubes reinforced composite conical shell with pretwist under the thermal environment. In this paper, four types of carbon nanotube grading are considered, wherein the distribution of carbon nanotubes are made through the thickness direction of the conical shell. An eight-noded isoparametric shell element is used in the present formulation to model the panel based on the first-order shear deformation theory. For moderate rotational speeds, the generalized dynamic equilibrium equation is derived from Lagrange’s equation of motion, neglecting the Coriolis effect. The finite element code is developed to investigate the effect of twist angle, temperature, aspect ratio, and rotational speed on natural frequencies. The mode shapes of a carbon nanotube reinforced functionally graded conical shell at different twist angles and rotational speeds are also presented.
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