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Fiber Reinforced Composites
Tensile Strength v. Strain

As a result of its light weight, high strength, extreme durability, stability under UV exposure, and chemical resistance, FRP (fiber reinforced polyester) has become established as a material of major importance in an ever-increasing number of applications. FRP can be molded into an infinite number of forms and surface finishes and is capable of meeting stringent design standards while at the same time providing major cost benefits.

Fiber reinforced composites typically contain one or more reinforcing fiber materials embedded in plastic resin. In many applications core materials are used to increase the section modulus.

Fiber reinforcements contribute the bulk of strength and stiffness to a composite. There are a number of such materials, including glass fiber, carbon fiber, Aramid fiber, Kevlar® and others, all of which come in a variety of different grades and types. The most widely used reinforcement in the FRP composites industry is glass fiber.

Cores are used to enhance the rigidity and strength of FRP composites. Cored products can have one smooth surface or both surfaces smooth with the core sandwiched in. Typical coring materials are detailed below.

The bulk component of FRP laminates, the plastic resin, serves two purposes: First, it holds the fiber reinforcements in place, and second, under applied force, it deforms and distributes stress amongst these fibers.

The most common type of plastic resin is unsaturated polyester. Other types of resin include epoxies, vinyl esters, phenolics, etc.

Below is a table detailing the characteristics and limitations of the most common types of thermosetting resins.

BFG, over the last twenty-five years, have developed a vast database of raw materials for the composites industry which is updated automatically through BFG's interactive vendor communication procedures, continuous in-house research & development programs and associations with leading international suppliers, research organizations and universities working in the field of composites.

BFG's wealth of knowledge in the composites field is infused into design concepts, the development of new products, and the re-engineering of existing products.  Our design and engineering capabilities enable us to offer and advise our clients on the best solution to fulfill their particular requirements.

Common Glass Fiber forms:
CHOPPED STRAND MAT (CSM) Supplied in roll form. This is a mat of randomly chopped strands held together by a light binder. It provides uniform strength in all directions.

WOVEN ROVING (WR) Is used in conjunction with chopped strand mat to provide bulk and directional strength to FRP laminates. Glass fibers are arranged at right angles to each other or in other positions so that their orientation provides balanced strength.

CONTINUOUS FILAMENT MAT (CFM) Properties similar to CSM. Used for RTM and VARI processes.

WOVEN GLASS CLOTH Produced by conventional textile weaving methods in virtually any variation. Thinner cloths make laminates of very high tensile strength and modulus.

GLASS FLAKES Used in resin-based coatings to reduce the permeability of moisture, vapors and solvents.

Industry Standard Core Types

BALSA WOOD Scored balsa wood core gives excellent compressive strength and stiffness in addition to good sound and heat insulation and positive flotation.

PVC FOAM Excellent elastic properties and resilience.

PU FOAM Economical and light weight core for non-dynamic product applications.

HONEYCOMBS Used for strong, lightweight structures. There are aluminum, Aramid and plastic honeycombs.

NON-WOVEN CORE MATS Provide stiffness improvement and weight reduction.

Characteristics and Limitations of
Thermosetting Resins

Resin Type Characteristics Limitations
Polyester Wide choice of resins
Cure at room temperature
Very good mechanical properties
Good chemical resistance
Good electrical properties
Some shrinkage on curing
Vinyl Ester Excellent mechanical properties
Excellent chemical resistance
Good fatigue resistance
Good toughness
Low water absorption
High cost
Some shrinkage on curing
Epoxy Excellent mechanical properties
Very good chemical resistance
Good thermal properties
Very good electrical properties
Low shrinkage on curing
High cost
Long cure cycles
Limited cosmetic properties


Mechanical & Thermal Properties of FRP Laminates
Compared with other Structural Materials

Material Specific
Modulus MPa
Strength MPa
Compressive Strength
Max. Working
Temp ºC
Conductivity W/mK
Coefficient xl0/ ºC
Aluminum 2.7 69 417 200 200 23
Concrete 2.4 15-35 3 40
Mild Steel 7.8 207 240 400 50 12
Stainless Steel 7.92 193 241 450 55 I5
FRP 1.5-2.2 7-53 80-900 130-520 170-250 0.2-0.3 10-30
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