Fibre Reinforced Polymer (FRP) composite is a type of material wherein a polymer is reinforced with fibers, falling into the category of composite materials. These materials are formed by dispersing particles of one or more materials within another material, creating a continuous network around them.
Distinguishing itself from traditional construction materials like Steel and Aluminum, FRP composites exhibit anisotropic properties, while Steel and Aluminum are isotropic. This anisotropy signifies that their properties vary depending on the direction of the fibers, with the highest mechanical properties aligning with the direction of fiber placement.
FRP composites boast a high strength-to-density ratio, exceptional corrosion resistance, and advantageous electrical, magnetic, and thermal properties. However, they are susceptible to brittleness, and their mechanical properties may be influenced by factors such as loading rate, temperature fluctuations, and environmental conditions.
The primary function of fiber reinforcement is to bear the load along the length of the fiber and provide strength and stiffness in a particular direction, often replacing metallic materials in structural applications that prioritize load-carrying capacity.
The utilization of FRP in engineering applications has led to significant advancements in construction functionality, safety, and economy, primarily due to their exceptional mechanical properties.
Components of Composite Materials
Fibers
The choice of fiber plays a crucial role in determining the properties of composite materials. Major types of fibers used in construction include Carbon, Glass, and Aramid. Composites are often named based on the reinforcing fiber, such as CFRP for Carbon Fiber Reinforced Polymer. Key properties that differentiate fiber types include stiffness and tensile strain.
Matrices
The matrix serves to transfer forces between the fibers and safeguard them from detrimental effects. Thermosetting resins (thermosets) are predominantly used, with epoxy and vinylester being the most common matrices. Although epoxy is favored over vinylester for its superior properties, it comes at a higher cost. Epoxy exhibits good strength, bond, creep resistance, and chemical resistance.
Types of Fibre Reinforced Polymer (FRP)
Glass Fibre Reinforced Polymer (GFRP)
Glass fibers are typically produced by mixing silica sand, limestone, folic acid, and other minor ingredients, which are then heated until they melt at approximately 1260°C. The molten glass is drawn through fine holes in a platinum plate, cooled, gathered, and wound. These fibers, woven into various forms, offer high electrical insulating properties, low susceptibility to moisture, and significant mechanical properties. Despite being impact-resistant, glass fibers are heavier compared to carbon or aramid.
Carbon Fibre Reinforced Polymer (CFRP)
Carbon fibers boast a high modulus of elasticity ranging from 200 to 800 GPa, with ultimate elongation between 0.3% and 2.5%. They do not absorb water, resist various chemical solutions, excel in fatigue resistance, and exhibit no corrosion or creep.
Aramid Fibre Reinforced Polymer (AFRP)
Aramid, short for aromatic polyamide, includes well-known trademarks such as Kevlar, along with other brands like Twaron, Technora, and SVM. Aramid fibers offer moduli ranging from 70 to 200 GPa and ultimate elongation between 1.5% and 5%, depending on quality. While they possess high fracture energy, aramid fibers are sensitive to elevated temperatures, moisture, and ultraviolet radiation, limiting their use in civil engineering applications.
Applications of FRP
- Carbon FRPs find applications in prestressed concrete, underwater piping, structural parts of offshore platforms, and areas where resistance to corrosion and electromagnetic transparency are paramount.
- CFRP composites are utilized for underwater pipes due to their increased buoyancy compared to steel, as well as in stairways, walkways, high-performance hybrid structures, and seismic retrofitting.
- FRP bars, sheets, and strips are employed for strengthening various structures made from concrete, masonry, timber, and steel.
- AFRP composites, with their high energy absorption, are suitable for strengthening engineering structures subjected to dynamic and impact loading, such as helmets and bullet-proof garments.
By incorporating these elements and refining the language for clarity and professionalism, the article provides a comprehensive overview of Fibre Reinforced Polymer composites and their diverse applications in construction and engineering.