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The influence of hygrothermal ageing on polymeric composite sandwich materials and structures

The influence of hygrothermal ageing on polymeric composite sandwich materials and structures
The influence of hygrothermal ageing on polymeric composite sandwich materials and structures

The moisture absorption characteristics of closed cell PVC foam core materials and hybrid fibre reinforced epoxy skins have been monitored over a 2 ½ year duration. The laminates exhibited pseudo-Fickian characteristics, while the foams showed evidence of a multi-stage uptake mechanism. The long-term foam absorption data could not be modelled adequately by existing analytical models and a hypothesis is given. The effects of hygrothermal ageing on material properties has been analysed using DMTA. Room temperature modulus degradation and improved glass transition temperatures were observed. A hypothesis is proposed to explain the seemingly contradictory results, based on plasticisation, postcure and property recovery upon drying. The results from the foam material are believed to be the most comprehensive to date.

To evaluate these effects in a structural context, sandwich construction tee joints were analysed, which represent the bulkhead to hull connections in marine craft and typically suffer from slamming loads in service. The stress distribution was analysed in six joint geometries under compression loading using thermoelastic stress analysis (TSA) and finite element analysis (FEA). The results highlighted areas for significant improvement in the design. An important contribution of this work is the application of TSA to determining the effects of hygrothermal ageing on the stress distribution in the tee joints. This shows excellent potential and the data obtained would be impossible to collect by any other means. The information obtained about the ageing of the individual sandwich materials used in conjunction with FEA has also shown significant promise in the prediction of mechanical behaviour in the structural context. The quantitative development of this combined approach will be invaluable in the future analysis of the hygrothermal ageing of foam cored composite sandwich construction.

University of Southampton
Earl, Jacqueline Sonia
8f84b528-a099-4a08-9927-f0bc5a2b294a
Earl, Jacqueline Sonia
8f84b528-a099-4a08-9927-f0bc5a2b294a

Earl, Jacqueline Sonia (2001) The influence of hygrothermal ageing on polymeric composite sandwich materials and structures. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The moisture absorption characteristics of closed cell PVC foam core materials and hybrid fibre reinforced epoxy skins have been monitored over a 2 ½ year duration. The laminates exhibited pseudo-Fickian characteristics, while the foams showed evidence of a multi-stage uptake mechanism. The long-term foam absorption data could not be modelled adequately by existing analytical models and a hypothesis is given. The effects of hygrothermal ageing on material properties has been analysed using DMTA. Room temperature modulus degradation and improved glass transition temperatures were observed. A hypothesis is proposed to explain the seemingly contradictory results, based on plasticisation, postcure and property recovery upon drying. The results from the foam material are believed to be the most comprehensive to date.

To evaluate these effects in a structural context, sandwich construction tee joints were analysed, which represent the bulkhead to hull connections in marine craft and typically suffer from slamming loads in service. The stress distribution was analysed in six joint geometries under compression loading using thermoelastic stress analysis (TSA) and finite element analysis (FEA). The results highlighted areas for significant improvement in the design. An important contribution of this work is the application of TSA to determining the effects of hygrothermal ageing on the stress distribution in the tee joints. This shows excellent potential and the data obtained would be impossible to collect by any other means. The information obtained about the ageing of the individual sandwich materials used in conjunction with FEA has also shown significant promise in the prediction of mechanical behaviour in the structural context. The quantitative development of this combined approach will be invaluable in the future analysis of the hygrothermal ageing of foam cored composite sandwich construction.

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Published date: 2001

Identifiers

Local EPrints ID: 464382
URI: http://eprints.soton.ac.uk/id/eprint/464382
PURE UUID: ed0f4887-43c5-4e36-8cc1-9cad16071eff

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Date deposited: 04 Jul 2022 22:22
Last modified: 23 Jul 2022 02:07

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Contributors

Author: Jacqueline Sonia Earl

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