TECHNICAL ARTICLE Influence of Conventionally Drilled and Additively Fabricated Hole on Tensile Properties of 3D-Printed ONYX/CGF Composites Gorrepotu Surya Rao, Ritam Paul, Samarjit Singh , and Kishore Debnath Submitted: 19 July 2022 / Revised: 27 September 2022 / Accepted: 1 October 2022 The need for fast fabrication of customized composite parts having complex designs and intricate geometries has grown significantly. These products are in prodigious demand in a variety of research and development laboratories as well as industrial and medical sectors. Additive manufacturing (AM) has emerged as a cost-effective solution to the rising demand of complex intricate composite products with reduced production time compared to the conventional approaches. The present paper focuses on the exploration of tensile characteristics of conventionally drilled and 3D-printed hole of ONYX/CGF-based 3D composite dog bone specimens printed by Fused Deposition Modelling (FDM) technique. The 3D printing of dog bone-shaped tensile specimens was carried out using ONYX as the matrix and continuous glass fibre (CGF) as the reinforcement. In the present investigation, important 3D printing experimental parameters such as infill density (30, 40 and 50%), glass fibre orientation (0°,0°-90° and 0°-45°-90°-135°) and infill geometry (triangular, hexagonal and rectangular pattern) were considered. A total of 18 tensile specimens were 3D printed using Mark Forge 3D printer. Among the 3D-printed specimens, 9 samples were 3D printed with a predefined hole of 4 mm, whereas the other 9 samples were 3D printed without the holes. Later, the samples were conventionally drilled with a 4-mm drill bit. Statistical analysis of the experimental results was also carried out using the L 9 orthogonal array considered for experimentation. The comparative study showed that the tensile strength of conventionally drilled composite exhibited better results than the 3D-printed hole counterpart. The optimal conditions for attaining maximum tensile strength of 3D-printed hole composite of ONYX/CGF were triangular infill geometry, 50% infill density and fibre orientation as 0°. Moreover, the optimal parameters for conventionally drilled composites were observed as rectangular infill geometry, infill density of 50% and 0°-90° fibre orientation. Keywords 3D printing, fibre orientation, infill geometry, infill density, tensile properties 1. Introduction In todayÕs consumer-dominated industrial era, the demand for faster manufacturing of parts with complex designs required for product specific applications is on the rise. The ever- increasing consumer demand for product-oriented specific parts with complex design and faster production of the final product has paved the path for Additive Manufacturing (AM). Nowa- days, a rapid revolution has been noticed in the medical applications through additive manufacturing. Corral et al. (Ref 1) investigated that steel-filled PLA composite scaffold exhib- ited better result than bronze-filled PLA and copper-filled PLA composite scaffold in the formation of stem cell without protein coating. Otero et al. (Ref 2) studied that AM technologies can be used for better understanding of internal organs and structures obtained from CT scan and MRI images that can be further converted to DICOM and .stl format for printing. In this regard, it gives a clear idea about the medical procedure and better understanding to the surgeon. 3D printing has been synonymous with next-generation manufacturing process in the manufacturing domain. 3D printing gives the ability to develop application-oriented parts with intricate designs, light weight along with good mechanical strength which cannot be achieved with the existing traditional machining processes Ref (3-5). Moreover, unlike traditional manufacturing processes, 3D printing involves low investment costs and reduced production time from design to final production (Ref 6). Various AM techniques which are widely in use are Fused Deposition Modelling (FDM) process, MultiJet 3D Printing (MJP) process, Stereolithography (SLA) printing process, etc. in which the materials are laid in layer-wise manner (Ref 7-9). Different materials such as thermo-plastics, resins, ceramics, metals and different fibres like carbon fibre, glass fibre, Kevlar are used to prototype a part using 3D printing (Ref 10-14). Among various materials, long carbon fibre (CF)-based composites have found extensive application in demanding areas of automobile and aerospace industry owing to its excellent corrosion resistance, high stiffness-to-weight ratio and good fatigue characteristic (Ref 15). However, it is a costly affair as compared to glass fibres (GFs) which are relatively less expensive. GFs also portray fairly good mechanical properties and are appropriate for parts that are less stringent on weight and strength (e.g. Gorrepotu Surya Rao, Ritam Paul, Samarjit Singh, and Kishore Debnath, Department of Mechanical Engineering, National Institute of Technology Meghalaya, Shillong, Meghalaya 793003, India. Contact e-mail: samarjitsingh05@gmail.com. JMEPEG ÓASM International https://doi.org/10.1007/s11665-022-07529-2 1059-9495/$19.00 Journal of Materials Engineering and Performance