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Study of Damping Capacity in Amorphous Carbon Fiber Reinforced Superhard Aluminum Matrix Composite

Author: WangHongMei
Tutor: LiAiBin
School: Harbin Institute of Technology
Course: Materials Science
Keywords: C_f/Al composites damping capacity solution and aging treatment finite element method.simulation
CLC: TB331
Type: Master's thesis
Year: 2008
Downloads: 69
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Abstract

On the purpose to research and develop structural-functional high damping composites, mechanical properties and damping capacities of superhard Meso-10 aluminum alloy and composites reinforced by amorphous carbon fibers XN-05C were investigated in the paper. The XN-05C/Meso-10Al composites and aluminum alloy were fabricated by powder metallurgy, followed by hot extrusion. The distribution of the fiber in composites and the tensile fracture were observed by Optical Micrograph (OM) and Scanner Electron Microscope (SEM).The microstructure of the reinforcement/matrix interface and the configuration of dislocations in the composites were investigated by Transmission Electron Microscope (TEM). The mechanical properties were examined by tensile and hardness tests. The strain dependent and temperature dependent low frequency damping capacities of these composites and alloys were studied by dynamic mechanical thermal analyzer (DMA-Q800). The process of solution and aging was maded and the influences on mechanical properties and damping capacities were studied after solutiont and aging treatment. The room damping capacity was simulated by FEM and damping mechanism was fully analyzed for low modul amorphous carbon fiber reinforced superhard aluminum composites. This paper revealed the low frequency damping behaviors and their influence factors of Meso-10Al alloys and composites, established a good foundation to develop high damping aluminum matrix composites.The results showed that carbon fibers were uniformly distributed in the Meso-10Al matrix. Meanwhile, no apparent reaction is found at interface between fiber and matrix, fiber and matrix were linked by weak interface. As the volume fraction increases, the mechanical property of composites decreases, but because matrix alloy was superhard aluminum alloy, so the mechanical properties of 10% and 15% composites were fulfilled for engineer application.The investigation of the curve of damping-strain amplitude at room temperatrue indicated that the curve showed strain amplitude dependent and independent regions, the curves were well interpreted by G-L dislocation model, and frequency has slight influence on the damping capacity. Compare with matrix alloy 10% and 15% composites had the better damping capacity, otherwise 25% composite had worse damping capacity. The investigation of the temperature dependent damping capacity showed that the damping capacity increased when the temperature increased or the frequency decreased. The damping peaks induced by interface slippage around 250℃were found in composites.The mechanical property and damping capacity of material were tested after solution and aging treatment, and found mechanical property and damping capacity improved best when material aging at 140oC.The mechanical property improved 30% and the damping value was two times of extruded material when material aging at 140℃Two damping peaks at 150℃and 250℃were found in composites after solution and aging treatment. It is thought that the first peak was formed by the dislocation movement dragging the point defects, and the second peak was formed by slippage of interface, and the two peaks were heat-activate.The damping capacity of multi-fiber reinforced superhard aluminum composites XN-05C/Meso-10Al was simulated dynamically by finite element method. The room damping capacity was induced by the plastic deform of matrix under cyclic outside force, and it is in good accordance with G-L theory of dislocation intemal friction, and the simulation results were in good accordance with the experiments. Through examination and simulation the damping mechanism analysis was carried out, and found that at low temperature the dominant damping mechanisms are dislocation damping and internal damping of carbon fiber, at high temperature the dominant damping mechanisms are internal damping of superhard aluminum alloy and interface sliding

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