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Mode-I fracture toughness of carbon fiber/epoxy composites interleaved by aramid nonwoven veils
Bertan Beylergil,Metin Tanoğlu,Engin Aktaş 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.31 No.2
In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with aramid nonwoven veils with an areal weight density of 8.5 g/m2 to improve their Mode-I fracture toughness. The control and aramid interleaved CF/EP composite laminates were manufactured by VARTM in a [0]4 configuration. Tensile, three-point bending, compression, interlaminar shear, Charpy impact and Mode-I (DCB) fracture toughness values were determined to evaluate the effects of aramid nonwoven fabrics on the mechanical performance of the CF/EP composites. Thermomechanical behavior of the specimens was investigated by Dynamic Mechanical Analysis (DMA). The results showed that the propagation Mode-I fracture toughness values of CF/EP composites can be significantly improved (by about 72%) using aramid nonwoven fabrics. It was found that the main extrinsic toughening mechanism is aramid microfiber bridging acting behind the crack-tip. The incorporation of these nonwovens also increased interlaminar shear and Charpy impact strength by 10 and 16.5%, respectively. Moreover, it was revealed that the damping ability of the composites increased with the incorporation of aramid nonwoven fabrics in the interlaminar region of composites. On the other hand, they caused a reduction in in-plane mechanical properties due to the reduced carbon fiber volume fraction, increased thickness and void formation in the composites.
Free vibration analysis of damaged composite beams
Yusuf Cunedioglu,Bertan Beylergil 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.1
In this study, free vibration analyses of symmetric laminated cantilever and simply supported damaged composite beams are investigated by using finite element method (FEM). Free vibration responses of damaged beams are examined using Euler Bernoulli beam and classical lamination theories. A computer code is developed by using MATLAB software to determine the natural frequencies of a damaged beam. The local damage zone is assumed to be on the surface lamina of the beam by broken fibers after impact. The damaged zone is modeled as a unidirectional discontinuous lamina with 0o orientations in this study. Fiber volume fraction (vf), fiber aspect ratio (Lf/df), damage length (LD) and its location (λ/L), fiber orientation and stacking sequence parameters effects on natural frequencies are investigated. These parameters are affected the natural frequency values significantly.
Free vibration analysis of laminated composite beam under room and high temperatures
Yusuf Cunedioglu,Bertan Beylergil 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.1
The aim of this study is to investigate the effects of the beam aspect ratio(L/h), hole diameter,hole location and stacking layer sequence ([0/45/-45/90]s, [45/0/-45/90]s and [90/45/-45/0]s) on naturalfrequencies of glass/epoxy perforated beams under room and high (40, 60, 80, and 100°C) temperatures forthe common clamped-free boundary conditions (cantilever beam). The first three out of plane bending freevibration of symmetric laminated beams is studied by Timoshenko’s first order shear deformation theory. For the numerical analyses, ANSYS 13.0 software package is utilized. The results show that the holediameter, stacking layer sequence and hole location have important effect especially on the second and thirdmode natural frequency values for the short beams and the high temperatures affects the natural frequencyvalues significantly. The results are presented in tabular and graphical form.
Free vibration analysis of laminated composite beam under room and high temperatures
Cunedioglu, Yusuf,Beylergil, Bertan Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.1
The aim of this study is to investigate the effects of the beam aspect ratio(L/h), hole diameter, hole location and stacking layer sequence ($[0/45/-45/90]_s$, $[45/0/-45/90]_s$ and $[90/45/-45/0]_s$) on natural frequencies of glass/epoxy perforated beams under room and high (40, 60, 80, and $100^{\circ}C$) temperatures for the common clamped-free boundary conditions (cantilever beam). The first three out of plane bending free vibration of symmetric laminated beams is studied by Timoshenko's first order shear deformation theory. For the numerical analyses, ANSYS 13.0 software package is utilized. The results show that the hole diameter, stacking layer sequence and hole location have important effect especially on the second and third mode natural frequency values for the short beams and the high temperatures affects the natural frequency values significantly. The results are presented in tabular and graphical form.