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Textiles in Bridge Engineering

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Textiles in Bridge Engineering

You are part of a junior engineering team advising on repairs to a footbridge in the UK. Read the project brief, use the data, and justify your recommendations. Textile composites are engineered materials made by combining strong fibres with a matrix, often a resin. They are not ordinary cloth.

Project brief and material evidence

A concrete footbridge support has small cracks and the deck needs strengthening. The council wants a repair that adds little weight and resists corrosion from rain and road salt. Engineers are considering fibre-reinforced polymer (FRP): strong fibres held in a polymer matrix. Fibres carry much of the pulling load; the matrix holds them in place and transfers force between them. FRP can be light and corrosion-resistant, but its performance depends on fibre direction, bonding, fire protection, cost and inspection. It does not automatically replace steel in every bridge. A weave holds fibres in crossing directions; unidirectional layers place most fibres along one direction.

Sample

Failure load (N)

Mass (g)

Plain weave glass-fibre composite

520

Twill weave glass-fibre composite

610

Unidirectional carbon-fibre composite

900

Investigate, interpret and recommend

1.In this brief, what does tensile strength describe?

Resistance to being pulled apart
Resistance to being squashed
Ability to absorb water
Mass per unit area

2.Which statement best explains the different jobs of the fibres and the polymer matrix in an FRP composite?

3.Choose the best option for strengthening a bridge deck mainly along its length, where the main pulling forces run in one direction.

Unidirectional fibres aligned with the length
Fibres aligned only across the width
Loose cotton fabric
A resin layer with no reinforcing fibres

4.Calculate the failure load per gram for the twill glass-fibre sample. Show your working and give your answer to one decimal place in N/g.

5.Which sample had the greatest failure load, and which had the greatest failure load per gram? Use the data to support both answers.

6.The twill sample carried more load than the plain weave sample. Give one reasonable explanation, then identify one reason these results alone cannot prove that twill is always better.

7.The bridge support is exposed to rain and road salt. Name one potential advantage of FRP over steel in this situation and one issue engineers still need to consider.

8.A repair must add as little mass as possible while providing high tensile strength. Recommend one sample from the data and justify your choice using both its mass and failure load. State one limitation of your recommendation.

9.A repair strip may experience pulling forces both along and across its length. Would you choose a single layer of unidirectional fibres or a woven reinforcement? Explain how the force directions affect your choice.