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Experimental analysis of stresses in bonded, pultruded composite structures

Experimental analysis of stresses in bonded, pultruded composite structures
Experimental analysis of stresses in bonded, pultruded composite structures
Pultruded composites are usually manufactured by pulling fibres that have been immersed in resin through a heated die. The material is layered, usually with the main component being a thick layer of unidirectional material (UD). This is often sandwiched between outer layers of a randomly orientated material. In the current work the outer layers comprise a chopped strand mat (CSM) material stitched on a woven roving mat, known as complex mat (CM). For protection purposes, a thin layer of material, known as a ‘surface veil’, that consists of thermoplastic fibres wetted with polyester resin is deposited on the surface. Investigations into bonded pultruded butt strap joints have been carried out by the authors showing that the joint efficiency was poor. This was attributed to damage initiating in the UD/CSM material interface, as a result of poor interlaminar mechanical properties, exacerbated by the large stress discontinuities at the adhesive/surface veil/CM and CM/UD interfaces. The failure essentially results in a detachment of the surface of the pultruded material. To identify a means of increasing the joint efficiency it is necessary to establish the stress distribution in the joint particularly at the interfacial layers in the pultruded material to define how the load is carried and transferred to each layer. To do this an experimental technique known as thermoelastic stress analysis (TSA) is used. TSA is a non-contact technique that provides a full field map of the stresses on the surface of a component. The application of TSA to composite materials is described in the paper. To obtain quantitative stress data from TSA it is necessary to ‘calibrate’ the materials; the calibration approach is also described in the paper. The TSA data provides a layer-by-layer map of the stresses from the joint interface on the surface through the complex mat layer into the UD. This approach has provided a new insight into pultruded joint behaviour and enabled improved validation of Finite Element Analysis (FEA).
Dulieu-Barton, J.
9e35bebb-2185-4d16-a1bc-bb8f20e06632
Gheradi, A.
ce412e71-da26-402d-840c-c3325bf7022a
Boyd, S.
bcbdefe0-5acf-4d6a-8a16-f4abf7c78b10
Thomsen, O.T.
f3e60b22-a09f-4d58-90da-d58e37d68047
Dulieu-Barton, J.
9e35bebb-2185-4d16-a1bc-bb8f20e06632
Gheradi, A.
ce412e71-da26-402d-840c-c3325bf7022a
Boyd, S.
bcbdefe0-5acf-4d6a-8a16-f4abf7c78b10
Thomsen, O.T.
f3e60b22-a09f-4d58-90da-d58e37d68047

Dulieu-Barton, J., Gheradi, A., Boyd, S. and Thomsen, O.T. (2007) Experimental analysis of stresses in bonded, pultruded composite structures. Novel Applications of Surface Modification (NASM 2007), Southampton, UK. 17 - 19 Sep 2007. 1 pp .

Record type: Conference or Workshop Item (Paper)

Abstract

Pultruded composites are usually manufactured by pulling fibres that have been immersed in resin through a heated die. The material is layered, usually with the main component being a thick layer of unidirectional material (UD). This is often sandwiched between outer layers of a randomly orientated material. In the current work the outer layers comprise a chopped strand mat (CSM) material stitched on a woven roving mat, known as complex mat (CM). For protection purposes, a thin layer of material, known as a ‘surface veil’, that consists of thermoplastic fibres wetted with polyester resin is deposited on the surface. Investigations into bonded pultruded butt strap joints have been carried out by the authors showing that the joint efficiency was poor. This was attributed to damage initiating in the UD/CSM material interface, as a result of poor interlaminar mechanical properties, exacerbated by the large stress discontinuities at the adhesive/surface veil/CM and CM/UD interfaces. The failure essentially results in a detachment of the surface of the pultruded material. To identify a means of increasing the joint efficiency it is necessary to establish the stress distribution in the joint particularly at the interfacial layers in the pultruded material to define how the load is carried and transferred to each layer. To do this an experimental technique known as thermoelastic stress analysis (TSA) is used. TSA is a non-contact technique that provides a full field map of the stresses on the surface of a component. The application of TSA to composite materials is described in the paper. To obtain quantitative stress data from TSA it is necessary to ‘calibrate’ the materials; the calibration approach is also described in the paper. The TSA data provides a layer-by-layer map of the stresses from the joint interface on the surface through the complex mat layer into the UD. This approach has provided a new insight into pultruded joint behaviour and enabled improved validation of Finite Element Analysis (FEA).

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More information

Published date: 18 September 2007
Venue - Dates: Novel Applications of Surface Modification (NASM 2007), Southampton, UK, 2007-09-17 - 2007-09-19
Organisations: Fluid Structure Interactions Group

Identifiers

Local EPrints ID: 49150
URI: http://eprints.soton.ac.uk/id/eprint/49150
PURE UUID: a0bf6803-9d94-4081-abf6-be71e642f02e

Catalogue record

Date deposited: 26 Oct 2007
Last modified: 11 Dec 2021 16:53

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Contributors

Author: A. Gheradi
Author: S. Boyd
Author: O.T. Thomsen

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