Microstructure-elastic property relationships in carbon fibers: A nanoindentation study. (1st November 2020)

• Record Type: Journal Article
• Authors: Shirasu, Keiichi; Goto, Kenta; Naito, Kimiyoshi
• Is Part Of: Composites. Number 200(2020)
• Publication Date: 2020-11-01
• Subjects: Carbon fiber -- Polymer-matrix composites (PMCs) -- Anisotropy -- Elastic constants; Composite materials -- Periodicals; Materials science -- Periodicals; Composite materials; Periodicals; Electronic journals; 620.118
• DOI: 10.1016/j.compositesb.2020.108342
• Languages: English
• ISSNs: 1359-8368

Abstract

Abstract: Carbon fibers with high axial stiffness and strength have been used to reinforce polymer-matrix materials in advanced composites. However, these fibers exhibit large anisotropies in the radial and axial directions. In addition, limited data has been reported on the elastic properties of fibers in other directions than longitudinal and transversal directions, and on the relationship between elastic properties and fiber structures. In this study, we prepared five epoxy composites each containing a different type of carbon fiber and used a nanoindentation method in combination with finite element analysis to investigate five elastic constants of the carbon fibers. The results demonstrate that the crystallite size and the orientation of its graphite-crystal inclusions affect the elastic constants c 11, c 12, c 13 and c 33, while the carbon fibers with well-aligned large-sized crystallite possess a large mechanical anisotropy. In contrast, the shear modulus ( c 44 ) is less affected by the alignment of the crystallite. Instead, the fibers with larger interlayer spacing of (002) basal planes and large crystallite size exhibit a smaller c 44 . Highlights: Five elastic constants were investigated for different carbon fibers through nanoindentation. Relationships between elastic constants and crystalline structures are discussed. Crystallite size and orientation affect the transverse and longitudinal elastic moduli. The shear modulus is influenced by the interlayer spacing and crystallite size.