Browsing by Author "Chi, Yang-Kai"

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Effect of fiber array on damping behaviors of fiber composites
(2008-10-01)
Tsai, Jia-Lin
;
Chi, Yang-Kai
;
機械工程學系
;
Department of Mechanical Engineering
This study aims to investigate the fiber array effect on modal damping behaviors of fiber composites. Three different fiber arrays, i.e., square edge packing (SEP), square diagonal packing (SDP), and hexagonal packing (HP), were considered to represent the microstructures of the unidirectional composites. Repeating unit cells (RUCs) suitable for describing the characteristics of the microstructure were adopted in the generalized method of cell (GMC) micromechanical analysis. The energy dissipation concept was then employed to calculate the specific damping capacities of composites in the material principal directions. The specific damping capacities obtained from micromechanical analysis were regarded as the equivalent damping properties homogenizing in the composites. In conjunction with the modal shapes of the composite structures determined from the finite element analysis, the specific damping capacity was extended to characterize the corresponding modal damping of the composite rods and plates. Both free-free and clamped-free boundary conditions were taken into account in the composite structures. Results indicated that the structures constructed from the composites with SDP fibers exhibit better damping behaviors than the other two cases. (c) 2008 Elsevier Ltd. All rights reserved.
Investigating thermal residual stress effect on mechanical behaviors of fiber composites with different fiber arrays
(2008)
Tsai, Jia-Lin
;
Chi, Yang-Kai
;
機械工程學系
;
Department of Mechanical Engineering
This study aims to investigate the thermal residual stress effect on the constitutive behaviors of fiber composites with three different fiber arrays, i.e., square edge packing, square diagonal packing, and hexagonal packing. The repeating unit cell (RUC) containing fiber and matrix phase was employed to describe the mechanical behaviors of fiber composites. For the fiber phase, it was assumed to be linear elastic, whereas the matrix was a nonlinear material. The generalized method of cell (GMC) micromechanical model originally proposed by Paley and Aboudi [Paley M, Aboudi J. Micromechanical analysis of composites by the generalized cells model. Mech Mater 1992; 14(2):127-39] was extended to include the thermal-mechanical behavior, from which the thermal residual stress within the fiber and matrix phases was calculated. Through numerical iteration, the constitutive relations of the composites in the presence of residual stress were established. Results show that for the composites with square edge packing, the mechanical behaviors are affected appreciably by the thermal residual stress. On the other hand, the composites with hexagonal packing and square diagonal packing are relatively less sensitive to the thermal residual stress. (C) 2007 Elsevier Ltd. All rights reserved.