The Refined Model of the Elastic-Plastic Dynamic Behavior of Reinforced Curved Panels Sensitive to Strain Rate

The initial-boundary value problem of dynamic elastic-viscoplastic deformation of flexible curved panels (shallow shells) with plane -cross and spatial reinforcement structures is formulated. The inelastic behavior of the materials of the composition components is described by the constitutive equations of the theory of plastic flow with isotropic hardening, and their sensitivity to strain rate is taken into account. The geometric nonlinearity of the problem is taken into account in the Karman approximation. The used kinematic and dynamic two-dimensional relations and the corresponding boundary conditions make it possible to describe, with varying degrees of accuracy, the mechanical bending behavior of shallow composite shells. This takes into account the possible weak resistance of such reinforced panels to transverse shears. In the first approximation, the used two-dimensional equations, the initial and boundary conditions degenerate into the relations of the traditional non-classical Ambartsumyan theory. For the numerical integration of the formulated nonlinear dynamic problem, an algorithm of time steps is applied, based on the use of an explicit scheme of the cross type. The elastoplastic and elastic-viscoplastic behavior of the reinforced cylindrical shallow shells under transverse dynamic loads generated by an air blast wave is investigated. Metal-composite and fiberglass thin-walled constructions are considered. It is shown that the refusal to take into account the dependence of the plastic properties of the components of the composition on the rate of their deformation does not allow adequately describing the inelastic dynamic behavior of both metal-composite and fiberglass shallow shells. It is shown that in the calculations of even relatively thin reinforced cylindrical panels (with a relative thickness of 1/50), the use of the Ambartsumyan theory leads to completely unacceptable results in comparison with the refined bending theory. It has been demonstrated that even for relatively thin curved fiberglass panels, replacing the traditional flat -cross reinforcement structure with a spatial structure with obliquely laid fiber families can significantly reduce not only the intensity of deformations in the binder, but also the maximum deflection values in modulus. For metal-composite shallow shells with a weakly expressed anisotropy of the composition, the positive effect of the indicated replacement of reinforcement structures is practically not manifested.

Development of a 3D printing method for the textile hybrid structure

PurposeThe development of a 3D printing method for the textile hybrid structure that can both be a solution to the conventional drawbacks of 3D printing method and a step forward to a garment making industry.Design/methodology/approachA novel 3D printing method using the textile hybrid structure was developed to generate 3D object without support structures.Findings3D printing of curved panels without support structure was possible by using fabric tension and residual stress.Practical implicationsGarment panels can be 3D printed without support structures by utilizing the idea of textile hybrid structure. Garment panels are expected to be modelled and printed easily using the Garment Panel Printer (GPP) software developed in this study.Social implications3D printing method developed in the study is expected to reduce the time and material previously needed for support structures.Originality/valueComprehensive preparatory experiments were made to determine the design parameters. Various experiments were designed to test the feasibility and validity of proposed method.

EFFECT OF PROCESSING PARAMETERS ON THE WIDTHS AND THICKNESSES OF THERMOPLASTIC COMPOSITES MADE BY AUTOMATED FIBER PLACEMENT

The advent of Automated Fiber Placement (AFP) machine has expanded the capacities to manufacture engineering structures using thermoplastic composites. Structures of cylindrical shapes, flat and curved panels can be easily made using this technique. As more applications and more studies have been made on this technique for thermoplastic composites, many issues have come up. One issue of importance is the variation of the width and thickness of the tow as it is deposited. As the melted thermoplastic composite tow is being pressed under the compression force of the roller, the material flows. This changes the width and the thickness of the tow. The values of the width and thickness depend on many parameters such as the properties of the substrate, the temperature of the material, and the applied pressure. This variation in width and thickness of the individual tow being deposited has an influence on the development of laps and gaps between the deposited tows. This paper presents some of the results on an investigation on the above topic. Widths and thicknesses of carbon/PEEK tows processed using an Automated Fiber Placement machine with a hot gas torch were examined. Preliminary results show that there is significant variation in the width and thickness of the tows upon deposition.