FRP, fiberglass reinforced plastic, is a composite made from fiberglass reinforcement in a plastic (polymer) matrix. By reinforcing the plastic matrix, a wide variety of physical strengths and properties can be designed into the FRP composite. Additionally, the type and configuration of the reinforcement can be selected, along with the type of plastic and additives within the matrix. These variations allow an incredible range of strength and physical properties to be obtained. FRP composites can be developed specifically for the performance required versus traditional materials: wood, metal, ceramics, etc.
Engineers can design the FRP composite to provide the needed characteristics, and avoid cost penalties of an over-engineered product.
Fiberglass fibers are made from molten glass extruded at a specified diameter.
The fibers are gathered into bundles and the bundles combined create a roving.
Rovings are a continuous rope, similar to twine, and are wound on a mandrel to form a ball called a doff. Reinforcements for FRP are made from rovings that are either chopped into short strands or woven into a cloth.
There are many factors that affect the reinforcement characteristics of fiberglass:
- Fiber and bundle diameter and type of glass
- Direction of the fiberglass reinforcement
- The amount of fiberglass reinforcement
- The physical contact (wetout) of the fiber with the polymer
All of these factors must be taken into account when designing a FRP composite so that the required physical property strengths are met.
There are two basic types of plastics/polymers: thermoplastic and thermoset. In general, FRP composites utilize a thermoset plastic.A plastic in which the polymer molecules are not crosslinked (not chemically bonded to other polymer molecules) is a thermoplastic. Since the molecules are not connected by crosslink’s, it allows the molecules to spread farther apart when the plastic is heated. This is the basic characteristic of a thermoplastic; the plastic will soften, melt, or flow when heat is applied. Melting the plastic and allowing it to cool within a mould will form the finished product. Typical thermoplastics are: polyethylene (PE)– used in making garbage bags; polyvinyl chloride (PVC)– used for house siding; and polypropylene (PP)– used as carpet fibers, packaging, and diapers.
A plastic in which the polymer molecules are crosslinked (chemically bonded) with another set of molecules to form a “net like” or “ladder-like” structure is a thermoset. Once crosslinking has occurred, a thermoset plastic does not soften, melt, or flow when heated. However, if the crosslinking occurs within a mould, the shape of the mould will be formed. Typical thermoset plastics are: unsaturated polyester (UP)– used for bowling balls and boats; epoxy– used for adhesives and coatings; and polyurethanes (PURs)– used in foams and coatings.
In addition to these basic characteristics, polymers provide the FRP composite designer with a myriad of characteristics that can be selected, depending on the application. Combined with reinforcement of the polymer matrix, a vast range of characteristics are available for FRP composites.
The properties of FRP composites are measured the same way that traditional materials are measured so that comparisons can be made for evaluation. Typical measurements include:
Describes how much of a load a material can take before it is crushed or fractured
A number associated with the flexibility or stiffness of a material. It indicates how far a material will bend when a certain load is applied to it. The lower the modulus, the more flexible the material.
Measures how much of a load a material can take before it fractures or breaks when it is in the process of being bent.
There are two primary impact tests; one is called IZOD impact and the other is called Gardner impact. IZOD impact measures the energy required to fracture or break a material when it is struck on its edge. Gardner impact measures the energy required to damage or puncture a material when it is struck on its front surface.
Rockwell or Barcol Hardness
Measures the surface hardness of a material. The higher the hardness value, the more resistant a material is to scratching, abrasion, and denting.
A number associated with pulling or stretching a material (tension) and how much it elongates when a certain load is applied to it. The lower the modulus, the more the material will elongate or stretch.
Measures how much of a load a material can take before it fractures or breaks when it is in the process of being stretched.
FRP products are extremely durable versus many traditional products. The thermosetting resin properties provide chemical, moisture, and temperature resistance, while the fiberglass reinforcement increases strength and provides good performance over a wide temperature range (the properties of thermoplastics are greatly affected by temperature).
FRP finishes can be either smooth or embossed. Testing has shown that either finish performs (cleans) as well as a#3 finish on stainless steel. Tests for bacteria and mould growth indicate that FRP does not support the growth of either.
An embossed finish has the added benefit of providing a more scuff resistant surface than smooth.
FRP can be modified with additives to meet the code requirements of the particular application, either building construction or use in OEM equipment.
Like other organic building materials (e.g., wood), products made of FRP resins will burn. When ignited, FRP may produce dense smoke very rapidly. All smoke is toxic. Fire safety requires proper design of facilities and fire suppression systems, as well as precautions during construction and occupancy. Local codes, insurance companies and any special needs of the product user will determine the correct fire-rated interior finish and fire suppression system necessary for a specific installation.
A composite is a solid material, made out of two or more constituent, different and distinct substances that retain their physical characteristics, while contributing desirable properties to the whole.
Composites and composite fabricating is not new. Actually, it is one of man’s oldest engineering methods. Composites, like straw reinforced mud, were used for construction in prehistoric times. Today, composites are everywhere around us. For example, most buildings are composites, made out of newer materials like steel reinforced concrete or various kinds of panels. Likewise, glass fiber reinforced polyester is used extensively for the construction of many products like boats and yachts, tanks or piping.
Composite materials are the constituent materials that are used to fabricate composite products. Three types of materials are mostly used, or overwhelm the industry today: The matrix is a form of glue that surrounds, supports and keeps together in position the reinforcement.
The reinforcement is usually some type fiber material in the form of fabric that exhibits some special physical characteristics (like mechanical or electrical).
The core is usually some type of solid lightweight material used in-between the layers of fiber reinforced matrix forming a type of sandwich structure.
When matrix and reinforcement are combined in a laminate to form a new material, the imparting special characteristics of each are combined and enhanced by synergism (=working together.) Moreover, core can be utilized to improve the stiffness and strength of the product even further, resembling the effect of steel ‘I’ beam at a very low weight.
Growing demand for better performance on products and materials has led to continuous developments on the field of composites. Advanced, special fibers (like carbon or aramid) or resins (like epoxy) and cores (like PVC foam or honeycomb), and new fabricating methods were developed and utilized to construct other materials or products that have outstanding mechanical properties thought to be “exotic” a few decades ago. Those advanced composites are used in many industries like aerospace, automotive, energy, important sports/recreation and just about everywhere low weight and other special properties are needed.
Year by year, more and more designers and engineers recognize the values of composites over other traditional materials like metal alloys, plastics etc. This is because composite material systems result in performance unattainable by their individual constituents. Fiber reinforced (FRP) products are more reliable, more durable, easy and safe to use, more economic to produce, and individually solve many problems and offer many benefits. As a result, manufacturers are abandoning old materials and fabricating methods and turn to composites. Composites are no longer just the privilege of aerospace, defense and high priced products. They are rapidly becoming a way of achieving high structural performance at a low cost. They are found in most of the cars we drive, in all busses and trains, boats, and recreation and sports equipment such as skis or canoes we use on the weekends.
Composites offer many advantages:
- Higher mechanical properties like strength and stiffness
- Lighter weight, higher performance
- Energy savings
- Durability, fatigue resistance and longer service life
- Impact resistance
- Dimensional stability
- Anisotropic properties
- Good chemical properties, corrosion resistance
- Fire retardance
- High temperature service
- Sevier environment outdoor service
- Low maintenance requirements
- Low thermal conductivity
- Low or custom thermal expansion
- Tailored energy conductivity, (e.g. can be used to amplify or dump vibration)
- Tailored transparency to radio frequency (reflection or dumping properties)
- Tailored electric properties (insulation or conduction capability)
- Tailored electromagnetic transparency
- Tailored properties make composite products irreplaceable for both telecommunication and stealth technologies
- Flexible, tailor design, part consolidation and freedom of shape
- Combination of many materials and inserts
- Lower capital investment for FRP manufacturing facilities
- FRP products are simpler, having fewer and larger parts
- Relatively low energy consumption to produce raw materials