Fiber Reinforced Polymer for Process Industry

Fiber reinforced composite materials have many advantages over traditional construction materials. The use of Fiber Reinforced Polymer (FRP) composite structures is growing very rapidly around the world. The need of light weight structural elements with high stiffness for industrial applications increase the demand for construction technology made of composite materials. Fiber Reinforced Polymers (FRP) is system comprising of

carbon, glass and aramid fibres in an epoxy matrix. The system is currently gaining popularity in application for structural strengthening, which includes seismic retrofit, pipe rehabilitation, blast mitigation and environmental protection.

INTRODUCTION

A civil composite material is defined as the composition of two or more different kinds of the material constituents combined together to obtain the desired properties. Fiber reinforced composite is composed of fibers embedded in a matrix. The fibers may be short or long, continuous or discontinuous and may be in one or multiple directions. Fiber reinforced composites offer many advantages over conventional isotropic materials such as steel, aluminum and other metals.

Most of the civil composites are unidirectional. The mechanical properties are superior in the longitudinal (fiber) direction, and are poor in the transverse direction where the polymer matrix controls the behavior. The excellent properties of the composites are achieved by the favorable characteristics of the two major constituents namely the fiber and the matrix. In low performance composites, the reinforcements, usually in the form of short or chopped fibers (particles), provide some stiffening but very little strengthening; the load is mainly carried by the matrix. In high performance composites, continuous fibers provide the desirable stiffness and strength, whereas the matrix provides protection and support for the fibers, and, importantly helps redistribute the load from broken to adjacent intact fibers.

The arrangement of the fibers in the structure is governed by the structural requirements and by the process used to fabricate the part. Frequently, though not always, composite structures are made of thin layers called laminate or plies. Within each lamina the fibers may be aligned in the same direction or in different directions. The mechanical and thermal behavior of a structure depends on the properties of the fibers and the matrix and the orientation of the fibers.

Selecting proper matrix and reinforcement is important to the composite properties, but more important is the way in which these constituent materials are arranged. The methods of combining these constituents have developed rapidly from predominantly manual placement, and other processes, resulting in great advances in precision, quality control and reproducibility. There are many methods for the composite arrangements and their lay up. Hand lay-up, Spray-up, structure RTM/RRTM, bulk molding compound, sheet molding compound, Injection molding FGRTP, filament winding and pultrusion. These all process are concerned with vacuum pressure bag molding, cold pressure molding, stamping, centrifugal casting, continuous laminating, pressure and roll bonding, plasma spraying techniques, powder metallurgy, controlled solidification and pneumatic impaction. Among all those process and techniques three process methods are of particular interest to the civil engineering; these are hand –lay up, filament winding and pultrusion, out of which hand lay up and pultrusion are described in concerned paragraphs.

Figure: Laminate, Fiber and Matrix

ADVANTAGES

In the past decades, lightweight bridge deck systems are made from Fiber reinforced Polymer (FRP). Composites have been developed and experimentally implemented in bridge structures. Israelis made the first pedestrian FRP composite bridge in 1975.Since then composite sandwich construction is playing an increasingly important role in the design of structures because of its exceptionally high flexural stiffness to weight ratio. FRP is made of non-corrosive and nonmetallic materials, which means that it is not subject to the corrosion issues that are common to steel. In addition, it has been shown to possess high tensile strength, and the newer generation of FRP bars can provide adequate ductility, which makes them suitable for structural uses. In addition, performing pieces for on-site construction can save time and energy and enable structures to be erected very quickly, cutting down on labor costs. According to the Construction Industry Institute, glass FRP bar may be a suitable alternative for steel reinforcing in architectural concrete, concrete exposed to de-icing salts, exposed to marine salts, or used near electromagnetic equipment. FRP can be used both for repair or freestanding structural purposes. Unlike other materials that may be used for repair and maintenance, FRP may be put in place permanently, without concern of replacement necessitated by corroded materials. In addition, it does not require significant amounts of demolition be done before repairs can be made. FRP “fabric” or sheets can be wrapped around concrete columns or beams to increase stiffness and durability. The sheets are glued to the structural elements using powerful adhesive, requiring less time and effort for installation than steel plates. FRP rebar is being considered for use in place of steel rebar, as it has been shown to possess high tensile strength and toughness that would make it a structurally sound replacement.

Major advantages of fiber-reinforced composites on traditional structural/construction materials can be listed as:

Lightweight (reduce the wt of conventional bridge by 70-80%)
High directional strength
High corrosion resistance
High weather resistance
High dimensional stability
Non-magnetic
Radar Transparency
High dielectric strength
Low maintenance
Long term durability
High impact strength
Ease in construction and can be put into the service in relatively short time.

USE IN PROCESS INDUSTRY

When metals are severe for chemical resistance, maintenance FRP composite can replace the need for different pressure vessels and tanks in process industry. Inspite of accurate calculation for overturning in severe wind, the use of FRP composites decrease the foundation weight which can take into consideration for the soil with less bearing capacity. Any size and shape of pipe, duct, fittings or other accessories in process industry can be made through FRP.

The followings are the specific major advantages for using FRP tanks and process vessels:

Highly resistance to most of the chemicals used today.
Will not crack, chip peel, rust, rot or decay.
Have a greater strength by weight than steel.
Resistant to ultra-violet light and plant corrosive environments
When insulated and/or heat traced they provide excellent thermal insulation with low heat loss.
Resistant to galvanic and stray electrical currents, a feature not available in many other materials

TECHNICAL AND BUSSINESS SCOPE

In spite of the manifold advantages of FRP composites, the cost factor always resists the enhancement of its applications. The key advantages of fiber-reinforced composites, such as free-form and tailored design characteristics, strength/weight and stiffness/weight ratios which significantly exceed those of conventional civil engineering materials, high fatigue resistance, and a high degree of inertness to chemical and environmental factors, are often overridden by high materials and manufacturing costs, particularly in direct comparison with conventional structural materials such as steel and concrete. However, the recent downturn in defense spending and the resulting need for new markets has spurred renewed efforts in reducing the costs of both raw materials and manufacturing processes, making composites more competitive to use in process civil structures applications. In addition, the anticipated availability of low-cost carbon fiber will allow composite composites to be competitively applied to a much larger class of civil infrastructure and offshore applications. These materials are easily applied to a variety of civil infrastructure, industrial facilities.

Similarly, although composite technology applied to the oil industry has much in common with aerospace, infrastructure and automotive, it also is driven by unique requirements, both technical and economic. Some applications will benefit significantly from technology transfer while other applications or issues require unique new developments to succeed. In addition, technology transfer can propagate in two directions. Research conducted in support of oil industry applications has generated several advanced capabilities, which could be helpful to other industries. Examples of frontier areas of research conducted for the oil industry include understanding of the mechanics of hybrid structures, design of ultra high strain components, and design of thick-walled tubular. In addition, very advanced failure prediction analytical methods have been developed in support of composite production riser and spoolable tubing projects. There are several areas in which more research is needed to advance the state of understanding to support the design of future oil industry applications. More work is still needed on hybrid structures. Most of the advanced applications will rely on combinations of carbon and glass to meet high performance requirements at minimum cost. The availability of low cost carbon will move toward greater carbon utilization.

Another interesting area which has surfaced in the development of certain applications is the requirement to resist ultra high impact loads.. Sensor technology is rapidly advancing in drilling and logging operations. It is not only possible to integrate fiber optics into the wall of composite tubes as transmission lines, but to better use the sensors themselves for structural integrity monitoring. The area of damage tolerance and repair are important as well as inspection and nondestructive test methods. The use of new materials and combinations of materials means that design allowable are not well established and safety factors have not been well defined. In addition, much work remains to be done to develop and translate advanced analytical methods into more automated design procedures.

Low-cost manufacturing will continue to play an important role in the successful economical development of new composite applications as will creative structural engineering to take advantage of the design flexibility offered by composite.

The technology developed will encourage and enable a broad range of new applications for composite technology in civil infrastructure, industrial facilities, and offshore oil and gas operations. Some of these potential new applications include creative concepts for long-life, low-cost, large structures/joining technology for bridge construction; growing design/manufacturing/construction with new materials/shapes/manufacturing technologies with safer, corrosion-free, and more cost-effective for industrial facilities; and a whole new series of products for the oil industry to enable the cost-effective development of ultra deepwater petroleum resources.

CONCLUSION

Although composites have been extensively developed and used in the aerospace industry, they need to be developed further in specific directions for use in civil infrastructure and process industries.

In fact, the extent of these applications will depend on (1) the resolution of outstanding issues such as repair ability, fire, durability and environmental concerns, (2) the extent to which automation in the manufacturing process can reduce cost, (3) the development of composite material based design concepts that optimize the use of the material,

(4) the availability of validated codes, standards, and guidelines which can be used as design references and tools by the civil engineering community, and (5) the degree of quality control and quality assurance which can be developed and provided during the manufacturing/installation phase utilizing unskilled general construction labor. There are several areas in which more research is needed to advance the state of understanding to support the application of fiber reinforced composites in future oil industry.

REFERENCES

• Kim, D.H(1995). Composite Structures for civil and Architectural Engineering.

• Hayer, Micheal W (1998). Stress Analysis of Fiber Reinforced Composite material.

• Paudel, Subash; “Development of FRP Composites and its application”, Masters Thesis.