Bending performance enhancement by nanoparticles for FFF 3D printed nylon and nylon/Kevlar composites

Abstract

Fused filament fabrication (FFF) has been a major 3D printing technique for making thermoplastic products for decades. However, FFF printing for thermoplastic composites with aligned continuous fibers has been reported with limited success for only several years. In this study, we introduce an enhanced FFF-based approach by incorporating nanoparticles to the thermoplastic composites with continuous fibers. Our investigation focuses on the bending properties of FFF-printed fiber reinforced composites with and without nanoparticles. With Nylon 6 (PA 6) being the matrix material, nanocomposite filaments are obtained by adding carbon nanotubes (CNTs), graphene nano platelets (GNPs), or amino (NH₂-) functionalized GNPs. Various PA 6 matrix nanocomposite filaments are prepared through mixing and filament extrusion process. The nanocomposite filaments are then 3D printed with or without continuous Kevlar fiber prepreg filaments. For 3D printed pure PA 6, the addition of 1 wt% GNP-NH₂ increases the flexural strength and bending modulus by 334% and 315%, respectively. For 3D printed PA 6/Kevlar composite, the addition of 1 wt% GNP-NH₂ increases the flexural strength and bending modulus by 195% and 35%, respectively. However, the addition of CNTs or GNPs (up to 1 wt%) is less effective as compared with GNP-NH₂. The underlying mechanisms are discussed based on the matrix/fiber interfacial analysis.