Xu, Dun (2011) Mechanical characterisation of micro-stereolithographic materials. PhD thesis, University of Warwick.

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Abstract

Promising techniques such as micro-stereolithography (MSL) are opening up practical potential for exploiting new ideas for specialized polymer-based Micro-Electromechanical systems (MEMS) through small-batch production. As the field matures and grows, substantial research and commercial development demands better understanding of mechanical properties of MEMS materials to fully explore the potential of this technology. Bulk properties derived from conventional testing of large specimens (at 10 mm order) cannot be trusted. However, small-scale specimens (less than 1 mm) introduce major challenges, such as handling and mounting. The aim of this study was to contribute towards an improved understanding of the mechanical properties of the polymers (MSL materials) with a strong emphasis on developing new metrology. It proposed and described a special form of test-rig and compatible special MSL specimen design. A uniaxial tensile approach was chosen, partly because it offered simpler uncertainty models. The prototype used deadweight loading through a notch flexure, which acted both as a spring in parallel sharing the same displacement with the specimen and as a linear guideway. The specimen was integrally fabricated with large clamping regions and support bars released by cutting. Stiffly constrained mounting and loading surfaces were used to clamp MSL specimens to the flexure, protecting them against parasitic motions during the test in combination. Strain was measured through an elongation measurement by high-sensitivity capacitive micrometry, knowing the specimen dimensions. Verification tests on the clamping conditions showed no significant evidence of sudden slip or creep. MSL specimens were fabricated by a projection-based Envisiontec Perfactory system using a commercial acrylate-based R11 resin. Substantial shrinkage and curl distortion had been observed, which greatly reduced the fabrication accuracy of the MSL specimens. Specimens with different UV exposures and different sizes were fabricated and tested for better understanding of the MSL fabrication process. Typically, Young’s Modulus was a little smaller than expected and certainly dependent on both size and process parameters (in the region studied).

Item Type:	Thesis or Dissertation (PhD)
Subjects:	T Technology > TK Electrical engineering. Electronics Nuclear engineering
Library of Congress Subject Headings (LCSH):	Three-dimensional printing, Microelectromechanical systems -- Design and construction
Date:	December 2011
Institution:	University of Warwick
Theses Department:	School of Engineering
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Chetwynd, D. G. (Derek G.), 1948-
Extent:	xx, 245 leaves : ill., charts
Language:	eng
URI:	http://wrap.warwick.ac.uk/id/eprint/49843

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