Session: 16-01-07: Polymers and Composites II

Paper Number: 166652

3D Printing of Continuous Hemp Fiber Reinforced Thermoset Composites 

The fabrication and use of natural fiber-reinforced composites enhances environmental friendliness and sustainability of composites. As awareness of environmental impacts grows, the application of these materials is increasing. Natural fibers are inexhaustive resources. They are agricultural and forestry by-products. They offer several advantages, including diverse sources, large reserves, low cost, and high bio-degradability. When used as reinforcement, natural fibers enable polymeric composites to achieve promising mechanical properties while reducing environmental impact.

3D printing has introduced a novel approach to advancing natural fiber-based composites. In particular, continuous fiber-reinforced composites are known for their superior mechanical properties. Numerous studies have been conducted on 3D printing of polymer matrix composites using continuous synthetic fibers. However, only a few studies have focused on 3D printing of continuous natural fiber-reinforced thermoplastic composites. Moreover, there is a significant lack of research on 3D printing of continuous natural fiber-reinforced thermoset composites.

This research aims to investigate the 3D printing of continuous hemp fiber-reinforced thermoset composites and evaluate their mechanical behavior. Hemp fibers are specifically known for toughness. The linear mass and density of the commercially purchased continuous hemp fiber was 459 tex and 1.35 g/c, respectively.

This study 3D printed continuous hemp fiber reinforced composites using a liquid photocurable thermoset resin. The density and room-temperature viscosity of the resin were 1.19 g/c and 2.7 Pa.s, respectively. An in-nozzle impregnation process was used to infuse the liquid thermoset resin into the hemp fiber. Ultraviolet (UV) light was used to solidify the resin on the print bed. A rectangular specimen was 3D-printed using a back-and-forth motion of the print nozzle to characterize its mechanical properties. The density of the printed specimen was measured using Archimedes’ principle, and was found to be 1.22 g/c. The fiber volume fraction of the printed specimen was measured using an analytical approach, and was found to be 15 %.

The quality of the printed composite lay-up was analyzed using a Keyence surface profilometer. The printed composite exhibited regular loops in one side and overlapping loops on the other. The layer height was approximately 1.7 mm. Surface was assessed by drawing a transverse line on the specimen, and measured line roughness ( was 210 μm.    

Tensile and flexural testing were performed on two-layer 3D printed unidirectional specimens. The average tensile strength and modulus were 21 MPa and 4.3 GPa, respectively. Scanning electron microscopy (SEM) was conducted on the fracture surface of the failed specimen under tensile loading. SEM images showed evidence of good impregnation of the thermoset resin within the fiber tow. Moreover, the flexural test was performed on the 3D printed unidirectional specimens with a span-to-thickness ratio of 32:1. The average flexural strength and modulus were found to be 68.3 MPa and 3.15 GPa, respectively. The strain before failure was 3.3%, indicating the high flexibility of the printed specimens.

Thus, this study highlights the potential for fabricating and utilizing natural fiber-reinforced thermoset composites with improved biodegradability and renewability.

Presenting Author: Swetha Manoharan North Dakota State University

Presenting Author Biography: Swetha Manoharan is PhD student at North Dakota State University. He doing research on 3D printing of natural fiber.

Authors:

Swetha Manoharan North Dakota State University
Gavin Kahn North Dakota State University
Md Zahirul Islam North Dakota State University
Prashant Lakhemaru North Dakota State University
Luke Gibbon North Dakota State University
Chad Ulven North Dakota State University