Deformable Bowtie Antenna Realized by 4D Printing

4D printing is utilized to fabricate of thermo-deformable bow-tie antenna to fulfill some special applications with limited space or changing antenna property. In this paper, 4D printing is used to manufacture nylon and carbon fiber laminated composite material. The bow-tie antenna is installed on the surface of the composite material, and the carbon fiber is energized and heated, which causes thermal deformation of the substrate to reconfigure the antenna feature. The deformation mechanism of the composite material is explained, the characteristics of the thermally deformed bow-tie antenna with power applied to carbon fiber are analyzed. The results show that the energized carbon fiber heats up, causing the structure to stretch to a flat, with a maximum gain of 2.37 dBi and the −10 dB bandwidth being 4.28–4.64 GHz and 5.16–5.52 GHz, and the half-power beamwidth is greater than 60°. The structure bends at a 30° angle with a maximum gain of 3.58 dBi in the absence of external power, delivering a −10 dB bandwidth range of 4.12–5.6 GHz and a half-power beamwidth close to 45°. The customization of antenna radiation patterns and antenna gain can be readily tuned with power control.

Investigation of damage accumulation and delamination propagation in polymer composite materials based on two-level fracture models

The work is devoted to the study of deformation and fracture processes occurring in layered composites under combined loading modes. The aim of the work is numerical analysis of different modes of fracture, which are simultaneously realized in the samples of laminated composite material. Models of laminated composite material with imitation of technological defects in the form of material debonding are constructed. The delamination process is implemented using the virtual crack closure technique. The processes of damage accumulation and fracture of laminated composites are set on the basis of the models for reduction of stiffness properties using the Hashin criterion and Matzemiller model. The models are based on the laws corresponding to brittle and plastic fracture. Several models of fracture and degradation of elastic properties have been compared. A multiscale approach was used to solve the difficulties related to the precise description of the composite's internal structure. The essence of the approach is that the analysis of a laminated composite can be performed on three different scales: macro level, meso level and micro level. At the macro level, an equivalent material is used for which the effective properties are determined by homogenization methods, in particular by the mean field method. The multiscale finite element modeling is implemented, in the course of which macroscopic parameters of material sample at each step depend on characteristics and properties of components at the micro-level. The behavior of two samples of laminated polymer composite material was studied with different configuration of embedded defects under the load of two types: uniaxial compression and torsion, and only uniaxial compression. The influence of internal defects on the processes of damage accumulation and material delamination has been established.

Fatigue Characteristics and Numerical Modelling Prosthetic for Chopart Amputation

This research is looking for three laminated composite material groups. These three groups were utilized in experimental investigation to find their mechanical properties. These properties have been used to design and manufacture a socket for a partial foot prosthesis using an ANSYS model. This socket was manufactured with a vacuum pressure device to improve its properties. The socket composite material was tested for tensile and fatigue properties; then, its results were used in the ANSYS model. The composite material matrix was laminated in an 80 : 20 ratio, and there were three types of reinforcement lamination material (Perlon, glass fiber, and carbon fiber). The mechanical property results of these tests were found as follows: using only-Perlon reinforcement, the properties are σ y = 33.6 MPa , σ ult = 35.6 MPa , and modulus of elasticity = 1.03 GPa ; using (3Perlon +2carbon fiber +3perlon) layers, the properties were σ y = 65.5 MPa , σ ult = 92.5 MPa , and modulus of elasticity = 1.99 GPa ; and using (3Perlon + 2 glass fiber + 3perlon) layers, the results were σ y = 40 MPa , σ ult = 46.6 MPa , and modulus of elasticity = 1.4 GPa . The ANSYS model used the boundary condition from the measured contact pressure between the socket and the patient’s stump. The MatScan (F-socket) pressure sensor utilized these interface pressure measurements. The maximum values for the pressure were found as follows: 190 kPa and 164 kPa, which are recorded in the posterior and lateral locations, respectively. The calculated factor of safety for the prosthesis that has been made from a selected composite material with the following layers (3 Perlon+2 carbon fiber+3 Perlon) is 1.037 which is safe for design prosthetic applications. From this study, more prosthetic designs can be modelled and manufactured using this approach. Prosthetics and orthotics are usually custom-made for each patient according to its specific requirements. So, it will be very helpful to find a procedure to analyze the prosthetics before manufacturing it.

Phenomenological Methodology for Designing Optimal Styling in the Design of Panels of Aircraft Structures Made of Laminated Composite Material

The article solves the problem of rapid design of optimal stacking of a polymer laminated composite material of the traditional scheme. The existing engineering technique for laying design is based on constructive-force decomposition. However, this approach does not take into account the joint work of the layers. A solution is proposed that is based on the search for phenomenological dependencies for designing optimal styling parameters. The problem is solved by calculating the carrying capacity of a large number of styling options, searching among them for optimal solutions.

Numerical and experimental investigation on nonlinear dynamic behavior of satellite antenna reflector mechanism considering geometrical nonlinear effect and laminated composite material

A nonlinear dynamic modeling method for a satellite antenna system composed of laminated composite shell reflector undergoing large rotation considering its geometrically nonlinear effect and material nonlinearity effect is proposed in this paper. The present model treats flexible appendages of a spacecraft mechanism as laminated composite material and takes into account the coupling relations between nonlinear constitutive relation of laminated material characteristics and large-angle maneuver. Then, the corresponding efficient formulations for laminated paraboloidal reflector based on higher order shear deformation theory and Hamilton's principle are developed to capture the correct dynamic response. Furthermore, the experiment for evaluating the dynamic behavior of laminated composite reflector is conducted; the vibration of the laminated composite material is smaller than that of isotropic material. Numerical results are in good agreement with those obtained from experiment to validate the correctness of the present modeling formulation. Finally, numerical simulations demonstrate that nonlinear stiffness terms and elastic force resulting from with different curvature and different laying angle have significant effect on the dynamic characteristics. The larger curvature of the reflector and the larger laying angle of the laminated composite material will induce the larger deformation of the reflector. The conclusion has important theoretical value and practical significance for the study of controlling the pointing behavior of satellite antennas.

Justification of producing quality heat-resistant composite material using metals of platinum group by method of magnetic spray

In the work the technological scheme of manufacturing of a laminated composite material (SCM) by the method of magnetron sputtering is shown. This scheme consists of several successive steps: applying a protective coating to the mandrel, depositing the composite material to the required thickness, removing the mandrel. To implement this scheme, an experimental setup was made. Cathodes made of heat-resistant materials are made. A sample of the Ir - W - Nb system was obtained. His microstructure was studied. The conceptual model of the system of quantitative indicators of the quality of composite material production is developed. The system of indicators allows to obtain mathematical dependences of the product quality indicators on the indicators of technological operations at all production stages, and therefore to justify the optimal parameters of these modes.