Strengthening of L-shaped composite laminates using carbon nanotube reinforcement and thin ply non-crimp fabrics

Arca, Miray Aydan
The advances in manufacturing technologies have increased the use of composite materials in complex shapes such as curved beams. However, use of composites in complex geometries creates a weakness at the curvature and causes delamination failure. Major objective is to provide solution for this problem without degrading properties or increasing the weight of the structure. In this study, the effect of CNTs in the resin and the use of non-crimp fabric on the fracture toughness and curved beam strength of laminates are investigated experimentally. Curved beam composite laminates were subjected to four-point bending loading according to ASTM D6415. Double cantilever beam (DCB) tests and end notch flexure (ENF) tests were conducted to determine mode-I and mode-II fracture toughness, respectively. In the first part, mode-I and mode-II fracture toughness of 3% CNT added laminates are found to be 25% and 10% higher, respectively, compared to prepreg-fabric laminates. However, detrimental effect on the curved beam strength was found. In the second part, changing the material type from unidirectional to thin-ply non-crimp fabric material increased the mode I, mode II fracture toughness and curved beam strength of the laminates. It is observed that the manufacturing defects are the potential failure initiation sides.


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In wind energy and aerospace industries, new advances in composite manufacturing technology enable to produce primary load carrying elements as composite materials in wide variety of shapes large such as an L-shape. However, due to the geometry, Interlaminar Normal Stresses (ILNS) are induced once a moderately thick laminate takes highly curved shape. In the curved part of the L-shaped structure, the development of ILNS promotes mode-I type of delamination propagation which is the weakest fracture mode. Thi...
Experimental investigation of dynamic delamination in curved composite laminates
Uyar, İmren; Çöker, Demirkan; Department of Aerospace Engineering (2014)
In the aerospace industry, high demand for lightweight structures is fostering the use of composite laminates in a wide variety of shapes, as primary load carrying elements. However, once a composite laminate takes a highly curved shape, such as an L-shape, high interlaminar stresses induced in the curved region causes dynamic delamination formation. This thesis discusses the experimental investigation of delamination in L-shaped CFRP composite laminates under quasi-static shear loading. An experimental set...
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Al-TiB(2) master alloys have received much attention in recent years owing to their potential as efficient grain refiners for aluminum foundry alloys. In this study, the process of production of master alloys was investigated to develop a low cost method, namely, slag-metal reaction. This method can be used to fabricate Al-TiB2 master alloy in situ from the TiO(2)-H(3)BO(3)-Na(3)AlF(6) and Al system. Since the price of the raw materials is low and the technology is simple, the processing technique appears t...
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The purpose of this work is to present some numerical results on nonlinear, snap-through buckling of shallow spherical shells made of laminated composite materials under general static loading. Isotropic shells are covered as a special case of the general problem. A special-purpose finite-difference computer program has been developed. Moreover, the general-purpose computer program ANSYS has also been used. Effects of various material properties on the nonlinear behavior of the shells are investigated. One ...
Sonat, Emine Evren; Özerinç, Sezer; Department of Mechanical Engineering (2021-12-10)
Carbon fiber reinforced polymer (CFRP) composites are increasingly used in the aerospace industry due to their high specific strength compared to conventional metallic materials. However, a significant shortcoming of these composites is their increased susceptibility to damage. Structural repair is a common method to restore the load-carrying capacity of a damaged part when the damage size exceeds the pre-defined tolerances. Scarf and stepped bonded repair methods are the primary choice for cases that requi...
Citation Formats
M. A. Arca, “Strengthening of L-shaped composite laminates using carbon nanotube reinforcement and thin ply non-crimp fabrics,” M.S. - Master of Science, Middle East Technical University, 2014.