Winistoerfer, Andreas Urs (1999) Development of non-laminated advanced composite straps for civil engineering applications. PhD thesis, University of Warwick.

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Abstract

The focus of this thesis has been the feasibility of a novel load transfer concept for a carbon fibre reinforced plastic (CFRP) tendon system using non-laminated pin-loaded straps. The principle of these straps is that, as the tensile load increases, the relative slip between the layers produces a more uniform strain distribution in the layers leading to a higher load carrying capacity than when the laminate is fully consolidated (i.e. a laminated strap). This principle has been shown to occur by observing relative displacement between individual layers and strain measurements.

Such components could be used for post strengthening purposes of existing structures. They have the potential to alleviate the current problems associated with the corrosion of externally applied steel reinforcement. Furthermore, the low density of CFRP’s in combination with appropriate design procedures can provide a cost competitive solution. This advantage of choosing a non-metallic material is strengthened when whole life cycle costs are considered since composites are expected to outlive the conventional repair materials.

One objective of the project was to develop a tape material with continuous parallel fibres at low cost. At the start of the project no material available was suitable in terms of cost or quality. To drive the cost of the material down, thin lamina tapes with a thermoplastic matrix were considered. The various manufacturing processes for thermoplastic prepreg tape were reviewed and the powder impregnation process was found to meet the project's specifications. This method can produce high quality prepreg at a higher production rate compared to pultrusion with a thermosetting matrix. Sulzer Innotec Ltd. had an existing aqueous powder impregnation facility for research and development purposes. The author collaborated with the company to make specific modifications to the facility with the objective of improving material quality. This was achieved towards the end of the project, and in the thesis this material is referred to as Tape IV.

Preliminary development work was carried out throughout the duration of the project to characterise five thermoplastic materials. Two practical connection methods where developed to anchor the final outer layer in the non-laminated strap option. It was found that the clamping method was superior to the fusion bonding method; both methods will, however, find applications. A new manufacturing process for laminated pin-loaded straps was developed and is reported.

The author used MARC K6.2, a commercial finite element software, to predict the stress concentrations in the region where the strap makes contact with the steel pin. The difficulties associated with the advanced numerical modelling included contact and friction. The required results from MARC K6.2 were highly dependent on a sliding velocity parameter for which no accurate value was known. Because of the lack of rigor in the formulation of the finite element model, the stress concentrations predicted could not be used to optimise strap detailing. For completeness the MARC K6.2 modelling is described and the results reported.

To exploit the technology, research and development work will be needed, and the thesis shows where there are gaps in our knowledge and understanding.

Item Type:	Thesis (PhD)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Library of Congress Subject Headings (LCSH):	Civil engineering, Buildings -- Maintenance and repair, Buildings -- Retrofitting, Carbon fiber-reinforced plastics, Concrete construction -- Maintenance and repair, Shear (Mechanics), Thermoplastics
Official Date:	20 May 1999
Dates:	Date Event 20 May 1999 Submitted
Institution:	University of Warwick
Theses Department:	Department of Engineering
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Meier, Urs, 1943- ; Mottram, J. Toby (James Toby), 1958-
Format of File:	pdf
Extent:	xvii, 170 leaves : illustrations, charts
Language:	eng

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