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Accelerated test methods for assessing environmental degradation of composite laminates.

Broughton, W R; Lodeiro, M J; Maudgal, S (2000) Accelerated test methods for assessing environmental degradation of composite laminates. NPL Report. CMMT(A)251

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This report provides an assessment of accelerated test methods evaluated within the “Composites Performance and Design (CPD2) Project - Life Assessment and Prediction”. The project is directed towards the development and validation of test methods and predictive methodologies that can be used for characterising the long-term properties and residual life/strength of polymer matrix composites. The report considers convenient methods for obtaining basic strength-time data for unconditioned and environmentally conditioned glass and carbon fibre-reinforced laminates. Environmental data from tensile and flexural tests conducted on unidirectional and cross-ply laminates are evaluated. The report examines methods for monitoring damage (i.e. transverse cracking) in cross-ply laminates and assesses elastic and strength property degradation as a function of degree of damage.
The report considers: (i) tensile testing of hot/wet conditioned unidirectional and cross-ply glass fibre-reinforced epoxy laminates (70 °C/85% RH for periods up to 12 weeks); (ii) tensile testing of chemically conditioned unidirectional glass fibre-reinforced epoxy laminates (sodium hydroxide and sulphuric acid solutions); (iii) static fatigue testing of unconditioned glass fibre-reinforced laminates; (iv) flexural properties of hot/wet conditioned unidirectional laminates at ambient and elevated temperatures (immersion in deionised water at 60 °C for periods up to 42 days); and (v) autoclave conditioning of flexural and tensile specimens manufactured from carbon and glass fibre-reinforced laminates (steam environment at 136 o C and 2.2 bar for periods up to 72 hours).
The principal conclusions that can be drawn from the results are: (i) standard test geometries in the international standards ISO 527-4 and ISO 527-5 are suitable for assessing the combined effects of environmental conditioning and/or static loads on tensile properties; (ii) transverse flexural properties are particularly sensitive to the combined effect of moisture and elevated temperature; (iii) autoclave conditioning can accelerate moisture absorption by a factor of 100 and is suitable for use with materials designed for hot/wet conditions; and (iv) classical laminate analysis combined with micromechanics can be used to predict elastic and strength properties of moisture conditioned materials. The report provides a summary of the results, including recommendations on preparation, testing and inspection of composite laminates.

Item Type: Report/Guide (NPL Report)
NPL Report No.: CMMT(A)251
Subjects: Advanced Materials
Advanced Materials > Composites
Last Modified: 02 Feb 2018 13:17
URI: http://eprintspublications.npl.co.uk/id/eprint/1791

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