Characterization and testing of over-molded hybrid composites comprised of discontinuous and continuous glass fiber polypropylene composites

The interest in fiber-reinforced thermoplastic composites for automotive, aerospace, and other structural applications has significantly grown because of the need for high-performance, lightweight, and recyclable materials. Over-molded thermoplastic composites combine the benefits of discontinuous and continuous fiber reinforced thermoplastic composites, such as great design flexibility and improved mechanical properties. This research focuses on the characterization and testing of hybrid thermoplastic composites made of long fiber reinforced thermoplastic (LFT) composite and unidirectional (UD) glass fiber thermoplastic composite by compression over-molding. The aim is to assess the mechanical properties of these hybrid composites with both quasi-static testing such as three-point bend and dynamic testing such as the impulse excitation technique (IET). Moreover, micro-CT complemented by burn-off tests was utilized to analyze the extent of variability concerning fiber orientation, fiber length, and fiber content across different regions of the molded panels. Results suggest important relationships between mechanical performance and fiber orientation. The IET results coincided with those from the three-point bend testing, indicating its potential as a suitable nondestructive technique for testing hybrid composites comprised of discontinuous fiber and continuous fiber thermoplastic composites. This study offers detailed information about the interrelationships among the processing, microstructure, and mechanical properties of hybrid glass fiber polypropylene composites while demonstrating the potential of using the impulse excitation technique for testing the hybrid composite.