Hayri Baytan Özmen

By Huseyin Ersen Balcioglu and Hayri Baytan Ozmen

Due to the high synergistic effects of the components, hybrid composite materials are more advantageous than nonhybrid composite materials for advanced engineering applications. Additionally, knitted fabrics may have a different behavior than woven ones. Although the nonhybrid composites have only one reinforcing fiber type, the hybrid composites have multiple reinforcing fibers. In this chapter, fracture characterizations of laminated composites reinforced with intraply pure and hybrid knitted fabrics are experimentally and numerically investigated under different loading conditions. For this purpose, pure (100%) and hybrid fabrics (50–50%), which have 1 × 1 rib-knitted structure, were knitted by using glass and carbon fibers. Also, hybrid fabrics were knitted in three different widths in order to investigate the effect of knitting pattern width on the fracture toughness. Fracture toughness and energy strain release rates of pure and hybrid Arcan test specimens were determined under mode I (0o), mixed-mode I/II (30o, 45o, and 60o), and mode II (90o) loading conditions. Also, the J-integral method was used to determine the fracture toughness. Experimental and numerical results were found to be consistent. When the results obtained from pure and hybrid fabrics are compared, it is seen that hybridization had positive effects on the fracture strength of composite material compared to pure glass/epoxy material. Additionally, as the width of the pattern decreased, the fracture strength of the hybrid composites increased. In this respect, the hybridization processing should be done in the narrowest pattern width for higher resistance to fracture.

Part of the book: Fracture Mechanics Applications

By Emre Kemer, Hasan Başak and Hayri Baytan Özmen

In this work, a switching linear quadratic integral (LQI) controller based on fuzzy logic is designed for the load-factor tracking problem of high-performance aircraft referred to as the Aero-Data Model in Research Environment (ADMIRE). ADMIRE is a new generation aircraft and has a wide flight operation envelope in terms of altitude and speed. Hence, it is difficult to design a flight controller to achieve a high tracking performance. First, the LQI controller is selected due to good tracking performance and robustness in the model dynamics. Combining switching LQI controller and fuzzy logic improves the transient performance of the closed-loop switched system. The results obtained with the fuzzy switching controller have been compared with the conventional LQI and the switching LQI in terms of robust demand tracking. The simulation results have demonstrated that the fuzzy switching controller is superior to the conventional LQI and switching LQI controllers due to better transient performance and robust stability.

Part of the book: Advances in Fuzzy Logic Systems