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

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Makina Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2019

Öğrenci: ONUR ÇAKMAKÇI

Danışman: FEVZİ SUAT KADIOĞLU

Özet:

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