Nonlinear behaviour and stress concentrations in natural fiber composites under transverse loading

Download
2019
Çakmakçı, Onur
Natural fiber reinforced polymer composite materials attracted attention of the researchers recently. Some of them, especially flax fiber composites, do have quite favorable mechanical properties compared to synthetic fibers like E-glass. In this study, micromechanical model of flax fiber reinforced composite under transverse loading is investigated and compared with conventional synthetic fibers. The study includes variety of strains and response of the material under large deformations. Finite element models employing representative volume elements like single fiber, hexagon and random are utilized. Fiber volume fractions of 40% and 60% are applied for the multiple fiber packaging types. According to the results, increasing fiber volume ratio affected the magnitude of the stress concentrations proportionally. Stress concentrations spread more uniformly with increasing strain inputs. The presence of neighboring fibers affected the stress concentrations of each other. Results of the comparison case studies revealed that stiffness contrast between fiber and the matrix significantly contributes to the high stress concentrations. The most uniform transverse stress concentration state observed was the flax fiber’s for all comparison cases with conventional fibers

Suggestions

Analytical modeling of fiber reinforced composite deep beams
Yağmur, Eren; Burak Bakır, Burcu; Department of Civil Engineering (2018)
Discrete fibers are often used as reinforcement to increase the tensile and shear strengths of concrete. For many years, the behavior of fiber reinforced composite members has been investigated both experimentally and analytically. The influence of fibers on the behavior of shear critical members is quite significant, therefore, it is inevitable to develop a method, which estimates the shear strength of fiber reinforced composite deep beams realistically. This is why one of the main objectives of this study...
Delamination of compressively stressed orthotopic functionally graded material coatings under thermal loading
YILDIRIM, BORA; Yilmaz, Suphi; Kadıoğlu, Fevzi Suat (ASME International, 2008-09-01)
The objective of this study is to investigate a particular type of crack problem in a layered structure consisting of a substrate, a bond coat, and an orthotropic functionally graded material coating. There is an internal crack in the orthotropic coating layer. It is parallel to the coating bond-coat interface and perpendicular to the material gradation of the coating. The position of the crack inside the coating is kept as a variable. Hence, the case of interface crack is also addressed. The top and bottom...
Diffusion and reaction in catalyst pellets with bidisperse pore size distribution
Doğu, Timur (1998-06-01)
Catalysts with bidisperse pore structures are extensively used in chemical industries. In such catalysts, diffusion and reaction in the microporous particles are preceded by diffusion in the macropores. The relative significance of macro-and micropore diffusion resistances on the observed reaction rates with Linear and nonlinear rate forms, heat effects, catalyst deactivation and selectivity problems in bidisperse catalysts are investigated in number of published works. In this article, a review of the mode...
Wearable supercapacitors based on nickel tungstate decorated commercial cotton fabrics
Hekmat, Farzaneh; Tutel, Yusuf; Ünalan, Hüsnü Emrah (2020-07-01)
Symmetric supercapacitors (SSCs) with remarkable energy storing capability, high specific power as well as long-term cyclic stability were fabricated from nickel tungstate (NiWO4) @ nickel oxide (NiOx) decorated commercial cotton fabrics (CCFs). A commercial cotton-based textile was first made conductive by the state of the art ultrasonic spray coating method. This was followed by chemical and electrochemical processes to decorate activated CCFs with NiO(x)and NiWO4, respectively. The assembled SSCs had the...
Stress redistribution around fiber breaks in unidirectional steel fiber composites considering the nonlinear material behavior
SABUNCUOĞLU, BARIŞ; Mutlu, Çağlar; Kadıoğlu, Fevzi Suat; Swolfs, Yentl (Elsevier BV, 2020-05-01)
The use of steel fibers as reinforcement in polymer composites is recently increasing thanks to their ductility, high stiffness and wide range of diameters. Unlike carbon and glass fibers, steel fibers often end up with a non-circular cross-section due to their manufacturing technology. This may influence the stress redistribution around fiber breaks, which is important in longitudinal tensile failure of unidirectional composites. A parametric study was performed by using 3D finite element models with rando...
Citation Formats
O. Çakmakçı, “Nonlinear behaviour and stress concentrations in natural fiber composites under transverse loading,” M.S. - Master of Science, Middle East Technical University, 2019.