Carbon fiber is composed of carbon atoms bonded together to form a long chain. The fibers are extremely stiff, strong, and light, and are used in many processes to create excellent building materials. Carbon fiber material comes in a variety of "raw" building-blocks, including yarns, uni-directional, weaves, braids, and several others, which are in turn used to create composite parts.
THe strength of a material is the force per unit area at failure, divided by its density. Any material that is strong and light has a favorable Strength/weight ratio.
Rigidity or stiffness of a material is measured by its Young Modulus and measures how much a material deflects under stress. Carbon fiber reinforced plastic is over 4 times stiffer than Glass reinforced plastic, almost 20 times more than pine, 2.5 times greater than aluminum.
Although carbon fiber themselves do not deteriorate, Epoxy is sensitive to sunlight and needs to be protected.
Resistance to Fatigue in Carbon Fiber Composites is good. However when carbon fiber fails it usually fails catastrophically without much to announce its imminent break. Damage in tensile fatigue is seen as reduction in stiffness with larger numbers of stress cycles, (unless the temperature is high)
Tensile strength or ultimate strength is the maximum stress that a material can withstand while being stretched or pulled before necking, or fail. Brittle materials such as carbon fiber do not always fail at the same stress level because of internal flaws. They fail at small strains. (In other words, there is not a lot of bending or stretching before catastrophic failure)
Depending upon the manufacturing process and the precursor material, carbon fiber can be quite soft and can be made into or more often integrated into protective clothing for firefighting.
Carbon fiber reinforced composites have several highly desirable traits that can be exploited in the design of advanced materials and systems. The two most common uses for carbon fiber are in applications where high strength to weight and high stiffness to weight are desirable. High toughness can be accomplished when combined with other materials. Finally, in addition to the basic mechanical properties, carbon fiber creates a unique and beautiful surface finish.
Although carbon fiber has many significant benefits over other materials, there are also tradeoffs one must weigh against. First, solid carbon fiber will not yield. Under load carbon fiber bends but will not remain permanently deformed. Instead, once the ultimate strength of the material is exceeded, carbon fiber will fail suddenly and catastrophically.
In the design process, it is critical that the engineer understands and account for this behavior, particularly in terms of design safety factors. Carbon fiber composites are also significantly more expensive than traditional materials. Working with carbon fiber requires a high skill level and many intricate processes to produce high-quality building materials (for example, solid carbon sheets, carbon fiber sandwich laminates, carbon tubes, etc). Very high skill level and specialized tooling and machinery are required to create custom-fabricated, highly optimized parts and assemblies.
When designing composite parts, one cannot simply compare properties of carbon fiber versus steel, aluminum, or plastic, since these materials are in general homogeneous (properties are the same at all points in the part), and have isotropic properties throughout (properties are the same along all axes). By comparison, in a carbon fiber part, the strength resides along the axis of the fibers, and thus fiber properties and orientation greatly impact mechanical properties. Carbon fiber parts are in general neither homogeneous nor isotropic.
The properties of a carbon fiber part are close to that of steel and the weight is close to that of plastic. Thus the strength to weight ratio (as well as stiffness to weight ratio) of a carbon fiber part is much higher than either steel or plastic. The specific details depend on the matter of construction of the part and the application.
Several structural engineering applications utilize carbon fiber reinforced polymer because of its potential construction benefits and cost effectiveness. The usual applications include strengthening structures made with concrete, steel, timber, masonry, and cast iron; Retrofitting to increasing the load capacity of old structures like bridges; to enhance shear strength and for flexure in reinforced concrete structures. Other applications include the replacement for steel, prestressing materials and strengthening cast-iron beams.
Carbon fibers are mostly used for repair purposes of the old structural element against shear and flexure failure, the material is known as CFRP.
AAKAAR aims at creating a platform to compete, learn and promote Civil Engineering amongst the education fraternity through Competitions, Events and ICES, IIT Bombay (research paper conference) and also to make a festival of all and for all the Civil Engineering students.