Gower, M R L; Shaw, R M; Broughton, W R (2008) Thick Composites: Part I:Mechanical Test Review, Part II: Cure Optimisation. NPL Report. MAT 24

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Abstract

Recent developments have seen an expansion in the use of composite materials in structural applications involving thickness sections in excess of 20 mm, often complex in shape. The general perception has been to associate through-thickness properties with thick composites, whereas in fact an equally important issue relates to the measurement of in-plane properties and the effect of physical size of test specimens on measured data. Although extensive developmental work has been undertaken worldwide into test methods and design procedures for in-plane properties of thin laminates, there are no standard test methods available that provide guidance on testing of thick composite sections. The approach generally adopted has been to use existing standards, developed for testing small laboratory-scale specimens, with non-standard (i.e. larger) specimen geometries. A major concern relates to whether data generated from standards for relatively thin specimens are equivalent to or representative of thick section mechanical behaviour.
This report reviews key issues relating to mechanical testing of thick composite sections, highlighting issues that need to be resolved or better understood in order for these materials to fulfil their full market potential. The report covers tension, compression, shear, flexure and multi-axial loading conditions, environmental, impact and fatigue resistance, and issues relating to manufacture and inspection of thick laminates. Work undertaken to assess the effects of cure on thick laminate properties and to formulate an optimised cure cycle for a 20 mm thick carbon fibre-reinforced plastic (CFRP) material is detailed. Recommendations are provided as to future work required for test method development for thick composite laminates.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	MAT 24
Keywords:	composites, thick sections, cure, mechnical, thermal
Subjects:	Advanced Materials Advanced Materials > Composites
Last Modified:	02 Feb 2018 13:15
URI:	http://eprintspublications.npl.co.uk/id/eprint/4135

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