Onur Çoban

Bio: Onur Çoban is an academic researcher from Kocaeli University. The author has contributed to research in topics: Adhesive & Dynamic mechanical analysis. The author has an hindex of 12, co-authored 38 publications receiving 994 citations.

Experimental investigation of single and repeated impacts for repaired honeycomb sandwich structures

Abstract: Single and repeated impact behaviors of repaired honeycomb sandwich structures which are used in cargo panels at A319/A320/A321 Airbus were examined. Firstly honeycomb sandwich composites with detected impact damages which are in the limits of Aircraft Maintenance Manual and Repair Manual were repaired according to these manuals. Preliminary single low-velocity impact loadings were performed for original and repaired samples in order to find the energy limits which were ranged from fully elastic energy level to perforation energy level. At low-velocity single impact loadings, impact properties and damage mechanisms which occurred at both surface and internal parts of the materials were discussed from force- deflection (F-D) curves. In the second part, low-velocity repeated impact tests were performed with the determined impact energy levels. Repeatedly impact loading properties were also discussed with F-D curves. Impact damages which occurred in front and rear faces of composite structures were determined with digital camera. According to experimental results it was determined that impact behavior of repaired honeycomb composites is sufficient to be used in aircrafts.

Effect of Fiber Orientation on Scratch Resistance in Unidirectional Carbon-Fiber-Reinforced Polymer Matrix Composites

Abstract: Polymer composites have been widely used in industrial applications because of their high-specific strength and modulus. During their maintenance and service life small scratches can be formed on the surface of the composite material. These small scratches can result in crack initiation causing material failure and also some esthetic defects. When we consider that polymer composites may have various fiber orientations, it is possible to develop a remarkable increase in their scratch resistance. For this reason it is necessary to investigate the effect of fiber orientation on scratch resistance for polymer composites. In this study, scratch resistance of continuous carbon-fiber- reinforced polyetherimide composites were investigated as a function of fiber orientations by means of CSM microscratch tester machine. During the experiments the relation between the scratch resistance and operational parameters are determined as a function of scratch hardness, penetration depth, and coefficient of friction.

Recent advances in novel metallic honeycomb structure

Abstract: Innovative honeycomb-based structures have been paid substantial attention in recent years due to their superb mechanical performances and specific functions. The presented study made acomprehensive overview on the development of the innovative honeycomb-based structures in the past two decades, including filled-type, embedded, tandem, hierarchical, auxetics with Negative Poisson's Ratio (NPR), etc. Mechanical performances of these structures were commented with advantages and disadvantages, related on their geometric configurations, mechanical performance and dynamic response, respectively. The challenges as well as future directions were also analyzed. The achievements provide significant guidelines in designing of new generation light-weight honeycomb-based structures.