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Title: Fracture mechanics approach to compare laser sintered parts and injection mouldings of nylon-12
Authors: Hitt, D.J.
Haworth, Barry
Hopkinson, Neil
Keywords: Fracture toughness
Nylon-12
Laser sintered
Injection moulded
Issue Date: 2011
Publisher: Sage Publications on behalf of Institution of Mechanical Engineers / © The Authors
Citation: HITT, D.J., HAWORTH, B. and HOPKINSON, N., 2011. Fracture mechanics approach to compare laser sintered parts and injection mouldings of nylon-12. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 225 (B9), pp. 1663 - 1672.
Abstract: In comparison to equivalent parts made by injection moulding, components manufactured by laser sintering are often perceived to offer inferior mechanical properties, yet the evidence for this is rarely based upon systematic research studies. In this paper, attempts have been made to conduct a fundamental study of the fracture behaviour of both injection moulded and laser sintered parts, based upon a modification of a standard technique used to determine linear elastic fracture mechanics parameters. The influence of specimen thickness (in the range 2–10 mm) was also included in the experimental plan, which concentrated upon the testing of single-edge notch bending (SENB) beam specimens. Force-displacement characteristics demonstrated significant plastic deformation in nylon (PA12) specimens, so that the J-integral method was used to obtain quantitative fracture parameters, including the energy requirements for crack growth. Comparisons of this parameter showed thickness-dependent ‘geometry-sensitive’ data for each set of samples. For the injection moulded SENB specimens, energy absorption decreased with increasing thickness, a result attributed to the influence of plane-strain-dominated conditions. In contrast, laser sintered samples exhibited increased toughness as specimen thickness increased towards 10 mm; this could not be explained by density or particle melting data and may be interpreted by changes in molecular structure that occur during the additive manufacturing process.
Description: This article was published in Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture [Sage Publications on behalf of Institution of Mechanical Engineers / © The Authors]. The definitive version is available at: http://dx.doi.org/10.1177/0954405411402141.
Sponsor: This work was supported by an EPSRC grant [grant number EP/E002323/1] to the IMCRC at Loughborough (IMCRC project number 251).
Version: Accepted for publication
DOI: 10.1177/0954405411402141
URI: https://dspace.lboro.ac.uk/2134/17391
Publisher Link: http://dx.doi.org/10.1177/0954405411402141
ISSN: 0954-4054
Appears in Collections:Published Articles (Materials)

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