Search

The objective of this research work was to gain a better understanding of the mechanical properties of epoxy resin composites reinforced with carbon fiber. For this purpose, the effects of fiber orientations, resin types, and number of laminates on mechanical properties of laminated composites have been investigated. In the sample preparation, composites were manufactured by hand lay-up process, using a fiber-to-resin ratio of 40:60 (w:w). To investigate the effect of fiber orientation, angles of 0°, 35°, 45°, and 90° were selected. Results show that the mechanical properties, in terms of tensile, flexural and impact strengths, were mainly dependent on the fiber orientations followed by the number of laminates. At a similar fiber orientation, the composites made with EM500 epoxy resin showed the highest mechanical properties (such as tensile and flexural and impact strengths) compared to other evaluated composites. However, the differences were not highly significant. The results indicated that the mechanical properties of composites made with five-ply were generally slightly greater than three-ply composites. It may be due to the bondline defects, which adversely influence the mechanical properties. Scanning micrographs of the composites showed that the epoxy matrix material was fully adhered to the fibers, indicating a strong interface. It can be concluded that the order of increment parameters in the mechanical properties of the composites is fiber orientation > number of laminates > resin type. In addition, the tensile and flexural properties were superior in case of ±35° fiber orientations. [ABSTRACT FROM PUBLISHER]

Based on the super twisting concept, this article develops an integral sliding mode controller with nonlinear disturbance observer for position control and extending the traveling range of an initially curved micro-beam. The nonlinear damped model of the curved micro-beam is modeled based on the non-classical continuum theory. The single-mode assumption is used to transform the nonlinear governing PDE of the system into a nonlinear state-space form. The robust controller is designed to overcome the position control problem in the presence of non-parametric uncertainties and unknown non-symmetric input saturation due to the existing constraints in the electrostatic actuation. The effects of the uncertainties are considered as a compound disturbance term which can be estimated in finite time. Furthermore, due to the estimation properties of the observer, knowledge about the bounds of the uncertainties is not required. Extensive simulation results clearly verified the effectiveness of the controller in position tracking and extending the traveling range of the initially curved micro-beam to the unstable zones under smooth control effort. [ABSTRACT FROM AUTHOR]