What is CFRP?
Carbon fibre reinforced polymer (CFRP) is a composite material consisting of carbon fibres and a polymer resin matrix. The carbon fibres provide the load bearing component of the material while the matrix is used to bind the fibres together into a set position and transfer the forces between the fibres. The matrix also prevents the fibres from buckling and protects them from environmental effects (Teng et al. 2002).
The carbon fibres are very stiff while the resin has a low density which leads to a light-weight material with a high strength to weight ratio. CFRP also boosts a number of additional favourable properties such as: |
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Applications of CFRP
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CFRP is currently being used in a number of industries. Initially its use was confined to the aerospace and automotive industries due to the high cost of the material. However as the technology developed the cost decreased which has allowed the material to be used in a wider range of applications.
The civil engineering industry also noticed the reducing costs of CFRP and began research examining the potential uses of it within the industry. Initially this largely focused on the strengthening of concrete structures. These strengthening techniques can be applied to beams, columns and slabs. Flexural and shear strengthening of beams (or both) is possible using CFRP (Teng et al. 2002). Flexural strengthening of a beam generally comprises of bonding a CFRP plate to the tension face of the beam. Shear strengthening can take one of three configurations:
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Each configuration comes with its own advantages and disadvantages and their suitability depends on the beam in question. The strengthening of columns involves enhancing the axial strength and ductility of concrete by lateral confinement. This is done by encasing the concrete with CFRP. The confinement can be carried out on site via wrapping or comprise of a prefabricated shell (Teng et al. 2002). The method of strengthening slabs with CFRP depends on the type of slab but generally involves bonding CFRP to the tension face.
As the level of research into the uses of CFRP within Civil Engineering has increased so has the number of potential application with CFRP being used as rebar in reinforced concrete structures as well as in strengthening schemes for masonry, timber and metallic structures. CFRP strengthening schemes for steel beams are similar to those used for concrete as they involve a plate being bonded to the steel structure. However, the difference in the modulus of elasticity between steel and CFRP leads to greater stresses in the bonding adhesive. This, coupled with the thermal effects that will be investigated in this project highlights the importance of being able to predict the behaviour of the adhesive joint. |