Experimental and numerical investigation of mechanical effect of externally weak layers in thick hybrid composites

Gul, Saher (2019) Experimental and numerical investigation of mechanical effect of externally weak layers in thick hybrid composites. [Thesis]

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There is a growing interest in the use of thick hybrid composite laminates in the structural elements of aerospace and hydrospace structures. As amount of composite materials used in aircraft structures has now exceeded 50% by weight, it is more crucial than ever to study their mechanical properties and failure behaviors. In the present work, the influence of weak external layers of carbon and glass fibers on the flexural behavior of thick carbon/glass fiber reinforced hybrid composite laminates was examined to monitor their failure mechanisms. In the first part, four types of symmetric laminate structures were designed by tailoring the stacking sequence of glass (G) and carbon (C) fiber reinforced prepregs. Hot Press Curing (HPC) technique was utilized for manufacturing of the laminates. In each composite structure, 48 prepreg plies were used; and their configurations were adjusted to (C8/G8/G8)s, (G8/C8/G8)s, (G8/G8/C8)s, and (C8/G8/C8)s. Flexural tests showed that the highest flexural strength (1260 MPa) was exhibited by the laminate with the configuration of (G8/C8/G8)s, and the highest flexural modulus (79.64 GPa) was shown by the laminate with configuration of (C8/G8/C8). In addition, Digital Image Correlation (DIC) technique was used for the full-field in-plane strain and displacement registration, and for the study of failure mode development during the bending tests. The results indicated that the type of fiber placed along the horizontal midplane of the laminate controlled the failure mode, and the type of fiber available on the faces governed the behavior of stress strain curve. The fracture surface characterization performed by optical and scanning electron microscopy techniques indicated that the compressive failures in the form of kink band formation and shear-driven interlaminar delamination were the two most prevalent forms of failure in thick hybrid laminates. In parallel to the experimental study, numerical study was carried out by Finite Element Method (FEM) to investigate the displacement values in the direction parallel and transverse to the loading axis, and for obtaining the longitudinal and shear strain values. Both experimental and numerical studies emphasized the importance of using stacking sequence of a thick hybrid laminate as a practical approach in controlling the flexural properties of the composites. To conclude, this work provides a new insight into the design and fabrication of thick-section hybrid laminates by the adjustment of their stacking sequence
Item Type: Thesis
Uncontrolled Keywords: Thick hybrid laminate composites. -- Digital image correlation. -- Finite element method. -- Flexural property. -- Kalın hibrit laminant kompozitler. -- Dijital görüntü korelasyonu. -- Sonlu elemanlar metodu. -- Eğme özelliği.
Subjects: T Technology > TS Manufactures > TS0155-194 Production management. Operations management
Divisions: Faculty of Engineering and Natural Sciences > Academic programs > Manufacturing Systems Eng.
Faculty of Engineering and Natural Sciences
Depositing User: IC-Cataloging
Date Deposited: 14 Feb 2020 09:56
Last Modified: 26 Apr 2022 10:32
URI: https://research.sabanciuniv.edu/id/eprint/39651

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