RESEARCH ARTICLE Epoxy composites integrated with functionalized wet-milled graphitic nanoparticles: Featuring enhanced mechanical performance and in-plane fracture resistance Lakshi Nandan Borah | Sudipta Halder | Pannalal Choudhury Department of Mechanical Engineering, National Institute of Technology Silchar, Silchar, Assam, India Correspondence Sudipta Halder, Department of Mechanical Engineering, National Institute of Technology Silchar, Silchar, Assam, India. Email: shalder@mech.nits.ac.in Funding information Science and Engineering Research Board, Grant/Award Number: EEQ/2018/001101; Department of Science and Technology, India, Grant/Award Number: SR/FST/ ETI-373/2014 Abstract Composites made of epoxy-based systems are popular in many engineering applications because of their enhanced mechanical performance, fatigue prop- erties, and other physical and thermal properties, but their low fracture tough- ness can limit their usefulness in high-performance structural applications. This study aims to enhance the fracture properties of epoxy-based composites by adding cost-effective ball-milled graphitic nanoparticles. Herein, dry ball milling for 15 and 48 h is done to produce ball-milled graphite (BMG) nano- particles. A significant reduction in particle size is achieved after 15 h of dry milling. Interestingly, a similar reduction in particle size is achieved for BMG (258 nm) when wet ball milling for 3 h is performed. These BMGs were sila- nized (SBMG@3) and incorporated into the epoxy network. We found even at a higher loading level of SBMG@3, the resulting nanocomposites exhibited a significant improvement in fracture toughness (2.47 MPa m 1/2 ) and energy (1.55 kJ/m 2 ). This improvement was attributed to the upliftment of the in- plane crack propagation resistance of the nanocomposites primarily offered by SBMG@3 due to coagulated interfacial interaction with the epoxy network that effectively hindered the propagation of the crack by providing numerous sites for energy dissipation, leading to improved fracture toughness. Our results demonstrate that SBMG@3 has great potential for improving the frac- ture toughness and energy of epoxy-based composites, making them suitable for various industrial applications. Highlights • Synthesized cost-effective 2D carbon nanofillers via high-energy ball milling. • To overcome the re-agglomeration effect wet ball milling is performed. • Transformation of natural graphite to BMG with sizes of 258 nm. • K IC and G IC improve to 2.47 MPa m 1/2 and 1.55 kJ/m 2 , respectively, for ECSB1. • FS and FM of the epoxy nanocomposites enhanced by 43.69% and 51.64%. KEYWORDS fracture, mechanical properties, nanocomposites, nanoparticles, particle size distribution Received: 22 May 2023 Revised: 31 July 2023 Accepted: 7 August 2023 DOI: 10.1002/pc.27681 Polymer Composites. 2023;44:7985–7996. wileyonlinelibrary.com/journal/pc © 2023 Society of Plastics Engineers. 7985