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Indentation analysis and mechanical modeling of multilayered composites


Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/9834

Indentation analysis and mechanical modeling of multilayered composites

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Title: Indentation analysis and mechanical modeling of multilayered composites
Author: Tang, Guanlin
Advisor(s): Shen, Yu-Lin
Committee Member(s): Shen, Yu-Lin
Al-Haik, Marwan
Khraishi, Tariq
Maji, Arup
Department: University of New Mexico. Dept. of Mechanical Engineering
Subject: nanocomposite
LC Subject(s): Nanocomposites (Materials)--Mechanical properties.
Nanocomposites (Materials)--Compression testing.
Ceramic-matrix composites--Mechanical properties.
Ceramic-matrix composites--Compression testing.
Layer structure (Solids)
Degree Level: Doctoral
Abstract: A numerical study was undertaken to investigate the mechanical properties of metal-ceramic nanolayered composites. The model system features alternating thin films of aluminum (Al) and silicon carbide (SiC). Finite element modeling was employed to analyze the nanoindentation and microcompression behavior. This modeling study treats the heterogeneous structure of the material explicitly, and seeks to correlate the overall material response with the intrinsic deformation characteristics. We first report on the nanoindentation behavior of the Al/SiC composites. Two material systems were considered: Al/SiC multilayers free of substrate and Al/SiC above the silicon (Si) substrate. The numerical model features a conical indenter within the axisymmetric simulation framework. For the Al/SiC multilayers free of substrate, a valid composite elastic response can be retrieved beyond a certain depth. The effective modulus was found to be representative of the out-of-plane modulus of the multilayer composite. For the Al/SiC multilayers above Si substrate, the effects of the substrate material and heterogeneity of the composite play an important role in the modulus and hardness determination. Significant tensile stresses can be generated locally along certain directions. The unloading process leads to an expansion of the tension-stressed area and continuation of plastic flow in parts of the Al layers. The unloading response is therefore much more complex than the conventional elastic recovery process as seen in homogeneous materials. Attention was then turned to the viscoplastic effects during indentation. Within the present modeling framework, we found that a hold time at the peak load can help to obtain a reliable hardness value, while elastic modulus does not seem to be affected by the hold. The multilayers display a less significant time-dependent behavior, compared to the case of a single-layer material. Finally we report on the composite pillar behavior under micro-compression tests. It was found that the base material connected to the pillar plays a significant role in the measured mechanical response. It is essential to take into account the base and indenter compliances to obtain a reliable stress-strain relationship. The multilayered pillar deforms in a non-uniform way under compression, especially when a tapered side wall included in the numerical model.
Graduation Date: July 2009
URI: http://hdl.handle.net/1928/9834

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