Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 23Citation - Scopus: 26Experimental and Statistical Analysis of Carbon Fiber/Epoxy Composites Interleaved With Nylon 6,6 Nonwoven Fabric Interlayers(SAGE Publications Inc., 2020) Beylergil, Bertan; Tanoğlu, Metin; Aktaş, EnginThermoplastic interleaving is a promising technique to improve delamination resistance of laminated composites. In this study, plain-weave carbon fiber/epoxy composites were interleaved with nylon 6,6 nonwoven fabrics with an areal weight density of 17 gsm. The carbon fiber/epoxy composite laminates with/without nylon 6,6 nonwoven fabric interlayers were manufactured by VARTM technique. Double cantilever beam fracture toughness tests were carried out on the prepared composite test specimens in accordance with ASTM 5528 standard. The experimental test data were statistically analyzed by two-parameter Weibull distribution. The results showed that the initiation and propagation fracture toughness Mode-I fracture toughness of carbon fiber/epoxy composites could be improved by about 34 and 156% (corresponding to a reliability level of 0.50) with the incorporation of nylon 6,6 interlayers in the interlaminar region, respectively. The results also revealed that the percent increase in the propagation fracture toughness value was 67 and 41% at reliability levels of 0.90 and 0.95, respectively.Conference Object Citation - WoS: 11Citation - Scopus: 14Quantitative Detection of Low Energy Impact Damage in a Sandwich Composite Wing(SAGE Publications Inc., 2010) Seaver, Mark; Aktaş, Engin; Trickey, Stephen T.This work describes damage detection in a foam core composite wing (1320 mm × 152.4 mm × 13.4 mm) following a series of low energy impacts. Thirteen impacts (6-8 J deposited energy) were applied at adjacent locations approximately 1/4 of the way out from the wing center. Following every one or two impacts, the wing was tested using static tip deflection and dynamic vibrational excitation. Static and dynamic strains were measured using eight fiber Bragg grating sensors. Dynamic acceleration was also monitored using three conventional accelerometers. The estimated bicoherence was used to detect the presence of damage-induced non-linearity in time-series data recorded from each sensor. Receiver operating characteristic (ROC) curves were constructed for each sensor based on 15 or more dynamic measurements made for each damage case. The ROC curves provide a quantitative, statistical approach to evaluating the damage detection capabilities of the various sensors.Article Citation - WoS: 2Citation - Scopus: 5The Influence of Low Energy Impacts on the Static and Dynamic Response of a Foam Core Composite Wing(SAGE Publications Inc., 2009) Aktaş, Engin; Seaver, Mark; Nichols, Jonathan M.; Trickey, Stephen T.; Davis, W. R.This work describes damage detection efforts on a composite wing subject to a series of low-energy (ĝ̂1/47 J) impacts. Two airfoils with fundamentally different damage scenarios were considered. The first damage scenario produced no visible signs of damage on the wing surface following eight impacts. A duplicate wing, subjected to a similar series of impacts, was investigated using flash thermography and subsequently autopsied. The flash thermography showed small, localized damage in the skin, but gave no information about core damage. The autopsy showed core/skin disbonding at both interfaces that varied with the number of impacts, core crushing, and a through the core shear crack. No clear changes to the static or dynamic wing response were observed for this scenario. The second damage scenario involved cracking of the wing skin. While damage quantification was not undertaken for this scenario, both static and dynamic changes in wing response were observed. An analytical model of the wing is presented which helps explain the observed behaviors of the two damage scenarios.