Experimental and homogenized orientation-dependent properties of hybrid long fiber-reinforced thermoplastics

This research presents a investigation of long fiber-reinforced thermoplastics (LFT) with mixed fiber types, combining experimental analysis with numerical modeling techniques. By accurately predicting the stiffness of mixed fiber composites, the design margin between mono fiber reinforced materials can be effectively exploited, facilitating the use of such materials. For this purpose in particular, a novel application of the Mori-Tanaka approach with two different inclusions guaranteeing symmetric stiffnesses is presented. This is a method that has never been used before in field studies. In addition, the study integrates fourth-order plate-averaged orientation tensors measured and subsequently interpolated to improve the accuracy of the modeling. Consistency with the established shear-lag modified Halpin-Tsai method is demonstrated, confirming the suitability of both approaches for predicting the tensile modulus of GF LFT and CF+GF LFT . However, discrepancies between predictions and experiments for CF LFT are attributed to the complex microstructure of the material caused by bundling and poor dispersion of the CF. Furthermore, the study reveals remarkable hybridization effects within the mixed fiber LFT, particularly evident in the 22% increase in elongation at break observed in CF+GF LFT compared to CF LFT . Overall, this research significantly advances the understanding and predictive capabilities regarding mixed fiber LFTs, which opens up a new design space of specific properties. This provides valuable insight for future research and industrial applications.