Development and Processing of Continuous Flax and Carbon Fiber-Reinforced Thermoplastic Composites by a Modified Material Extrusion Process

Abstract

Additive manufacturing, especially material extrusion (MEX), has received a lot of attention recently. The reasons for this are the numerous advantages compared to conventional manufacturing processes, which result in various new possibilities for product development and -design. By applying material layer by layer, parts with complex, load-path optimized geometries can be manufactured at neutral costs. To expand the application fields of MEX, high-strength and simultaneously lightweight materials are required which fulfill the requirements of highly resilient technical parts. For instance, the embedding of continuous carbon and flax fibers in a polymer matrix offers great potential for this. To achieve the highest possible variability with regard to the material combinations while ensuring simple and economical production, the fiber–matrix bonding should be carried out in one process step together with the actual parts manufacture. This paper deals with the adaptation and improvement of the 3D printer on the one hand and the characterization of 3D printed test specimens based on carbon and flax fibers on the other hand. For this purpose, the print head development for in-situ processing of contin uous fiber-reinforced parts with improved mechanical properties is described. It was determined that compared to neat polylactic acid (PLA), the continuous fiber-reinforced test specimens achieve up to 430% higher tensile strength and 890% higher tensile modulus for the carbon fiber reinforcement and an increase of up to 325% in tensile strength and 570% in tensile modulus for the flax fibers. Similar improvements in performance were achieved in the bending tests.

A comprehensive review on natural fillers reinforced polymer composites using fused deposition modeling

“…The stiffness and maximum curved bending force load of the 3D‐printed CFFRP specimens both increased by 39% and 115%, respectively. Kuschmitz et al [ 159 ] studied the tensile and flexural characteristics of continuous flax, carbon fiber, and PLA composites. The authors used the in‐situ approach to create composites, which they compared to neat PLA.…”

“…Due to high mechanical strength, continuous fibers have recently gained attention from researchers. Kuschmitz et al [ 159 ] improved the tensile performance by 325% compared to pristine PLA. Similarly, Hinchcliffe et al [ 76 ] enhanced the tensile and flexural strength by 116% and 16%, respectively.…”

Stress-adapted fiber orientation along the principal stress directions for continuous fiber-reinforced material extrusion

“…1a). This approach has already been studied and demonstrated in various research papers [13][14][15][16][17][18]. Another concept involves fiber impregnation prior to the process.…”

“…The use of continuous fiber reinforcements leads to a significant increase in the strength of the parts. The mechanical properties of continuous fiber reinforced parts fabricated using different approaches and materials have been described in detail in numerous studies [14][15][16][17][20][21][22][23][24]. The mechanical properties obtained depend on a number of factors.…”

Mechanical Properties of Polylactide Admixed with Carbon Nanotubes or Graphene Nanopowder

“…The results showed that the relative fiber content has a significant influence on the mechanical properties and the ratio of carbon fibers in composites. The authors of paper [17] dealt with the adaptation and improvement of the three-dimensional printer, and the characterization of printed specimens based on carbon and flax fibers. Paper [18] concerns the analysis of a biocompatible graft copolymer (3,4-ethylenedioxythiophene) manufactured by a 3D-printing melt extrusion method.…”