Carbon
fiber reinforced polymer (CFRP) is a type of composite materials consist of
carbon fiber and polymer. The carbon fiber provides the strength and stiffness
while the polymer acts as cohesive matrix to protect and held the fibers
together. CFRP are manufactured as a strips, bars, and sheets using different
production technique like filament winding, pultrusion, and hand lay-up
processes.
CFRP
materials possess good rigidity, high strength, low density, corrosion
resistance, vibration resistance, high ultimate strain, high fatigue
resistance, and low thermal conductivity. They are bad conductors of
electricity and are non-magnetic.
The
CFRP provide remedies for many problems associated with the deterioration and
strengthening of infrastructure such as bridges and buildings. Using CFRP
reinforcing bars in new concrete can eliminate potential corrosion problems and
substantially increase a member’s structural strength.
Effective
use of carbon fiber reinforced polymer could significantly increase the life of
structures, minimizing the maintenance requirements. Carbon fibers have also
been used as reinforcement for ablative plastics and for reinforcements for
lightweight, high strength and high stiffness structures.
Properties
of CFRP
- Alkali resistant.
- Corrosion resistance that is why it is used for corrosion control and rehabilitation of reinforced concrete structures.
- It has low thermal conductivity.
- CFRP has high strength to weight ratio and hence it eliminates requirements of heavy construction equipment and supporting structures.
- It needs short curing time. Therefore, the application takes a shorter time. This reduces the project duration and down time of the structure to a great extent.
- CFRP possess high ultimate strain
- High fatigue resistance. So, they do not degrade, which easily alleviates the requirement of frequent maintenance.
- CFRP is bad conductor of electricity and is non-magnetic.
- Due to its lightweight, prefabricated components in CFRP can be easily transported. This thus encourage prefabricated construction, reduce site erection labor cost and capital investment requirements.
Applications of CFRP in Concrete Structures
1. CFRP Strips
There are many techniques that use CFRP
strips, laminates for strengthening concrete structures such as Externally bonded
CFRP sheets and Near Surface Mounted FRP. The performance of the strengthening methods
depends on the strength of the adhesive used to bond CFRP to the concrete
surface and the degree of stress at the interface of the concrete and CFRP.
CFRP is used to strengthen steel
road bridges more easily and cheaply. The CFRP strips are only 20% of the
weight of the strips of similar products made from high-strength steel but are
at least four times as strong. Their high-strength-to- weight ratio makes the
CFRP strips easily to handle and reduces installation costs. Strips of CFRP
measuring just 8 mm in thickness have been used to strengthen a road bridge in
Rochdale, UK.
2. CFRP Wraps
CFRP wrapping is used for
rehabilitation of masonry columns. CFRP wraps are used for corrosion control
and rehabilitation of reinforced concrete columns. They are also used for
construction of earthquake resistant structures.
The addition of CFRP sheets greatly
increases the ultimate flexural moment capacity of the retrofitted shear wall.
However, in order for the FRP sheet to carry the high axial loads resulting
from the bending moment imposed on the shear wall, the CFRP sheets must be
adequately anchored at the base of the wall.
3. CFRP Laminates
Low Thermal Expansion CFRP Laminates
are used for strengthening of structural members such as beams in buildings and
girders in bridges. CFRP is used to strengthen steel road bridges more quickly,
cheaply and easily.
4. CFRP Bars
CFRP bars have been in the construction
of new buildings and strengthening reinforced concrete structures using Near Surface
mounted CFRP Reinforcement technique.
Manufacturing
Methods for CFRP
- Continuous reinforcement process
- Filament winding
- Pultrusion
- Hand lay-up processes
- Moulding processes
- Matched-die moulding
- Autoclave moulding
- Vacuum bagging
- Resin injection processes
- Resin transfer moulding
- Reaction injection moulding