Impact Behavior and Failure of 3D Printed Reinforced Composites
Authors: Liu Xiaofang , Saigal Anil , Zimmerman Michael 
Published: February 2024

Abstract
Additive manufacturing technologies have developed in leaps and bounds over the past few decades. Various additive manufacturing techniques have contributed to the development of new advanced materials and advanced structures. With the high strength and stiffness, lightweight structures, high temperature resistance, and corrosion resistance, composite materials have particularly facilitated the development of aerospace, railway transportation, automotive, marine, and robotics industries. In conjunction with additive manufacturing techniques, 3D printed carbon fiber reinforced composites as well as structures have prospective applications and research value in the study of new advanced materials.
Onyx is a composite material used in 3D printing that consists of nylon and chopped carbon fibers. This unique combination of materials yields a strong, durable material with many applications in the aerospace, automotive, and medical device industries. It can be used individually or as a matrix material mixed with other fibers to generate new advanced materials through fused deposition modeling (FDM) method. However, impact events are commonly possible in the aerospace and automotive industries, and there is a scarcity of knowledge regarding the puncture impact behavior of this material. Thus, in this study, the Onyx material was examined by employing the multi-axial impact test, following the procedures specified in the standard ASTM D3763-2018.
The purpose of this paper is to investigate the ability of the Onyx material to resist impact loading and the toughness of this material at different impact velocities, infill patterns, and infill densities. The test specimens were all printed using a Markforged Onyx One 3D printer based on the standard ASTM D3763-2018 and multiple puncture resistant tests were conducted on an Instron Dynatup 9250. Experimental results indicated that the energy absorption capacity of this material exhibited an upward trend with the increasing impact velocities for the given hexagonal infill pattern test specimens (with the infill density of 27%). With the highest impact velocity of 6.67 m/s, the maximum absorbed energy obtained was 2.64J, which was a 37% rise compared to the energy obtained by the test specimen with an impact velocity of 1.67 m/s. The energy absorption of test specimens with different internal structures (triangular, hexagonal, and rectangular) also behaved differently at a given impact velocity (3.33 m/s). It was found that the triangular infill pattern test specimen has the best energy absorption capacity, followed by the hexagonal infill pattern and finally the rectangular infill pattern, at 4.90J, 3.66J and 2.73J, respectively. For the given infill pattern test specimens at the same impact velocity of 3.33m/s, the absorbed energy increases as the infill density rises. As the infill density of the hexagonal test specimen increased by 10%, the energy absorption increased by 43%, while the rectangular test specimen showed an increase of 63% in energy absorption with a 13% rise in infill density.
The failures of the Onyx material under these circumstances were also specifically analyzed based on the standard ASTM D3763-2018. It can be concluded that impact velocity, internal structure, and infill density have a substantial influence on the impact performance of the Onyx material. This paper can provide an important reference for the design of new materials and structures incorporating this material, contributing to the development of new advanced materials and structures with better puncture impact resistance.