Davies, A*; Foreman, A*; Shaw, R M; Sims, G D (2001) Fibre reinforced plastic composites - machining of composites and specimen preparation. Measurement Good Practice Guide. 38

Text (Measurement Good Practice Guide No. 38) mgpg38.pdf - Published Version Download (1MB)

Abstract

The confidence placed in design data obtained from testing composite materials can depend greatly on the quality of the specimen used. Although, in principle the use of rectangular blanks as the staring point in most cases suggests specimen preparation is straightforward, there are many aspects that affect the quality of the measured data. For example, for unidirectional material loaded in either tension or compression, it is necessary to transfer the load into the specimen via protective tabs as it is not possible to use threaded or pin connections; or to use high grip pressures, due to the low interlaminar and transverse strength. Hence end tabs must be used that are well bonded to the specimen to avoid premature failure. In addition, for compression testing of these relatively thin laminates, as well as the test machine loading axially, the tabbed specimen must be symmetrical.
The guide provides background information on all stages and aspects of machining and specimen preparation and reviews Good Practice in the preparation of specimens of composite materials, which in this context are polymeric matrices, both thermoset and thermoplastics, reinforced by fibres with a length greater than 7.5 mm in the starting material or compound. In recognition, of the wide range of materials involved and the range of machine equipment in use, the guide concentrates on good practice procedures and is not prescriptive on feed, speed etc. Included are experiences gained during the research programme covering machining trails and the results of industrial reviews of current practices with results given from Round-Robin participation. Also included, as an annex is a guide procedure that will be proposed as a future standard similar to ISO 1818 that deals with unreinforced or short and particulate reinforced polymers. Attention is also drawn to ISO 1268 for test plate preparation as the source of most test specimens.
The preparation procedures have been incorporated onto a laminated card, which can be used as a check-list using a non-permanent marker, or photocopied for completion as part of the specimen preparation QA records.

Item Type:	Report/Guide (Measurement Good Practice Guide)
Keywords:	composites, adhesives, test specimens, machining, bonding
Subjects:	Advanced Materials Advanced Materials > Composites
Last Modified:	02 Feb 2018 13:17
URI:	http://eprintspublications.npl.co.uk/id/eprint/2313

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