Pultrusion of glass fiber reinforced polypropylene bidirectional composites and their mechanical performance

Despite the advantages of thermoplastic resin, pultrusion process has struggled to create bidirectional laminates, resulting in weaknesses in joint connections and transverse properties. To tackle this issue, the study focuses on developing a methodology for pultruding bidirectional laminates. Initially, two types of sheet thermoplastic prepreg of glass fiber and polypropylene were produced: one with transverse (90°) orientation of fibers and another with longitudinal (0°) orientation of fibers. These sheets are then integrated into a single pack where fibers are oriented both transversely and longitudinally, and fed into the pultrusion machine. The resulting strip profiles (75 × 3.5 mm) demonstrate threefold increase in pin-bearing strength and transverse properties, showing a considerable promise for applications that demand robust joint connections and dimensional stability. The addition of transversely reinforced plies makes it possible for the pultruded profile to meet the EN 13706-3 requirements to mechanical performance. The bidirectional thermoplastic profiles produced in this study demonstrated high mechanical properties and are suitable for use in composite structures with bolted joints.