ABSTRACT
As matrix material in PMCs, thermoplastic polymers are used in much larger volumes than thermosetting polymers. However, most of the thermoplastic matrix composites used today are injection-molded short E-glass fiber-reinforced thermoplastics. They are used in numerous household, industrial, commercial, and automotive applications. Fibers in these composites are typically 1–3 mm in length, and they are randomly oriented. Injection-molded thermoplastic matrix composites with fiber lengths of up to 12 mm, known in the plastics industry as long fiber thermoplastics or LFTs, are also available and finding increasing number of applications in the automotive industry. Increased fiber length in LFT improves the modulus and strength, but they are still much lower than the modulus and strength of continuous fiber-reinforced thermoplastics. On the other hand, the processing of continuous fiber-reinforced thermoplastics is significantly more difficult and expensive than injection molding short or long fiber-reinforced thermoplastics due to the difficulty of incorporating continuous fibers in thermoplastic polymers. For this reason, even though continuous fiber-reinforced thermoplastics possess several advantages over continuous fiber-reinforced thermosets, such as lower processing time, higher fracture toughness, long shelf life, and recyclability, their applications are still very limited.
