Applications Of Micro-Raman Spectroscopy In Mechanical Measurements Of Micro-Structures And Materials

With the rise of the micro/nanotechnology, how to accurately measure and evaluate the mechanical behaviors of micro-structures and materials has become the focus of multidisciplinary fields. It is an imp ortant a nd urgent issue t o de velop ne w experimental m echanical t esting an d ch aracterization t echniques t hat can b e effectively used at microscale. Micro-Raman spectroscopy is a potential experimental mechanical means which has been rapidly developed and applied in micromechanics recently. A s a n opt ical t esting t echnique, i t ha s m any advantages s uch a s non-destructive, non-contact, real time measurement, high spatial resolution, and high sensitivity to the material deformation. In this thesis, the micro-Raman technique i s applied to mechanical measurements of micro-structures and materials.First, the multiscale synergetic measurement system combined with macro tensile testing, m icro R aman m easurement, an d m eso el ectron m icroscopy analysis w as developed t o a nalyse t he m echanical pr operties of c arbon na notube (CNT) fibers prepared from chemical vapor deposition process, which are featured by multi-level structures. T he m ultiscale de formation c haracterizations of t he fiber unde r tensile loading were experimentally measured. Based on van der Waals interaction analysis, a two-level i nterfacial m echanical m odel was p resented t o an alyze t he i nterfacial bonding s trengths of m esoscopic bundl es a nd m icroscopic na notubes. F urther, t he mechanical be havior of m ulti-level i nterfaces during t he f iber de formation w as investigated. The strengthening and toughening mechanisms of the CNT fiber as well as i ts cr itical f actors were d iscussed o n t he b asis o f ex perimental r esults an d theoretical analysis.Second, a s applications in microscale m echanical measurement, mic ro-Raman spectroscopy was used to analyse the residual stress of multilayer film Si-substrate structure and t he s train di stributions a11he c rack t ip of carbon f iber reinforced composites. In the former measurement, the di stribution of residual stress along the cross section of Si substrate was experimentally evaluated and the stress in the film was calculated according to the mechanical balance of the structure. In the latter case, the distribution characteristics of normal strain and shear strain fields at the crack tip which pr opagates a long t he a xial di rection of t he c arbon fiber i n c omposites w as experimentally studied based on the Raman strain rosette technique.Overall, not onl y were the quantitative m echanical m easurement and analysis of micro-structures and materials achieved b y mic ro-Raman s pectroscopy, but it also demonstrated that the multiscale synergetic testing based on m icro-Raman technique is an effective method for microscale experimental mechanics.