Fiber Glass Reinforced Plastic

a composite material consisting of glass fibers embedded in a synthetic polymer resin. The fibers usually take the form of strands, rovings, fabrics, mats, and chopped strands. The resins are polyesters, phenol-formaldehydes, epoxies, silicones, polyimides, aliphatic polyamides, and polycarbonates.

Fiber glass reinforced plastics possess a desirable combination of properties. They have high strength and good dielectrical properties, relatively low density, low thermal conductivity, and high resistance to the effects of the atmosphere, water, and chemicals. The mechanical properties of the plastics are for the most part determined by the characteristics of the fiber and the strength of the bond between the fiber and resin; the temperatures at which the plastic is processed and used depend on the resin. Fiber glass reinforced plastics containing continuous fibers arranged in a particular fashion have the highest strength and rigidity (see Table 1). The arrangement can be parallel or can be one in which the fibers form angles with one another, angles that are constant or that vary throughout the material. By changing the arrangement of the fibers, the mechanical properties of the plastics can be varied within wide ranges. Fiber glass reinforced plastics in which the strands are distributed at random exhibit high isotropy of mechanical properties; included here are laminates made with granular and felted molding compounds, mat-base laminates, and laminates made with chopped strands that are sprayed onto the mold simultaneously with the resin.

Fiber glass reinforced plastics can be used at temperatures up to 60°-150°C when made with polyester resins, 80°-200°C with epoxy resins, 150°-250°C with phenol-formaldehyde resins, and 200°–400°C with polyimide resins. The dielectric constant of fiber glass reinforced plastics varies from 4 to 14, and the tangent of the dielectric loss angle varies from 0.01 to 0.05. Upon heating to 350°–400°C, these properties are more stable for plastics made with silicone and polyimide resins.

Plastics reinforced with fibers that follow a particular arrangement are manufactured by winding, by contact molding, or by laying up the laminae in an autoclave, vacuum bag, or pressure bag. Plastics consisting of molding compounds are manufactured by pressing and casting.

Fiber glass reinforced plastics are used as structural thermal insulating material in the bodies of boats, launches, ships, rocket engines, automobile bodies, cisterns, mobile refrigerator units,

Table 1. Typical properties of certain plastics reinforced with fibers of aluminoborosilicate glass
Property	Ordered arrangement of continuous fibers in the form of strands and rovings			Random distribution of short fibers
Property	Unidirectional	Crossed (at an angle of 0° and 90°)	Glass-fabric laminates	Molding compounds (l = 5–30 mm)**	Premixes (l = 5–25 mm)	Materials made by spraying chopped strands (l = 30–60 mm)	Mat-base (l = 20–70 mm)
*kgf = kilogram-force
**/ = fiber length
Density ...............	1.9–2.0	1.8–1.9	1.7–1.8	1.6–1.9	1.7–2.0	1.4–1.6	1.4–1.6
Tensile strength
In meganewtons/m² ...............	1,300–1,700	500–700	400–600	50–150	40–70	90–200	40–150
In kgf*/mm² ...............	130–170	50–70	40–60	5–15	4–7	9–20	4–15
Static bending strength
In meganewtons/m² ...............	800–1,200	700–900	600–700	140–300	80- -120	100–250	50–200
In kgf/mm² ...............	80–120	70–90	60–70	14–30	8–12	10–25	5–20
Modulus of elasticity
In giganewtons/mm² ...............	45–50	30–35	25–30	10–15	7–10	6–10	5–10
In kgf/mm² ...............	4 500–5 000	3,000–3,500	2,500–3,000	1 ,000–1 ,500	700–1 ,000	600–1 ,000	500–1 ,000

radio-transparent shields, helicopter blades, exhaust pipes, parts of machines and instruments, corrosion-resistant equipment and pipelines, small buildings, and swimming pools. The plastics also find use as electrical insulating material in electrical engineering and radio engineering.

REFERENCE

Plastiki konstruktsionnogo naznacheniia. Moscow, 1974.

V. N. TIUKAEV