No longer is product design constrained to the property limits and performance characteristics of unmodified grades of resins. The performance gain of these composites usually more than compensates for their higher cost.
Processing usually involves the same methods used for unreinforced resins.
Practically all thermoplastic resins are available in glass-reinforced compounds. Those used in largest volumes are nylon, polypropylene, polystyrene, ABS, and SAN, probably because most experience with reinforced thermoplastics has been based on these resins. Glass-fiber reinforcement improves most mechanical properties of plastics by a factor of two or more. Reinforced polyester has double the tensile and impact strength and four times the flexural modulus of the unreinforced resin. Also improved in reinforced compounds are tensile modulus, dimensional stability, hydrolytic stability, and fatigue endurance.