Issue 78

N. Nayak et alii, Fracture and Structural Integrity, 78 (2026) 378-392; DOI: 10.3221/IGF-ESIS.78.22

Study on multi-response optimization of mechanical, dielectric properties and fracture surface of alkali-treated sisal fibre reinforced polypropylene composites

Narayan Nayak, H. N. Reddappa, Nagaraja C. Reddy Department of Mechanical Engineering, Bangalore Institute of Technology, Bengaluru – 560004, Karnataka, India nayak.narayan0510@gmail.com; https://orcid.org/0009-0003-8394-4989 reddyhn@gmail.com; https://orcid.org/0000-0001-8127-9397 cnraaja@gmail.com; https://orcid.org/0000-0001-9240-9388 Ravikumar M* Department of Mechanical Engineering, B.M.S. College of Engineering, Bull Temple Road, Bengaluru -560019, KA, India ravikumarm.mech@bmsce.ac.in; https://orcid.org/0000-0002-4958-839X

Citation: Nayak, N., Reddappa, H.N., Reddy, N.C., Ravikumar. M.,Study on multi-response optimization of mechanical, dielectric properties and fracture surface of alkali treated sisal fibre reinforced polypropylene composites, Fracture and Structual Integrity, 78 (2026) 378-392.

A BSTRACT . This study investigates alkali-treated sisal fibre reinforced polypropylene composites produced by compression moulding, with particular attention to how fibre treatment, fibre length and fibre loading jointly influence mechanical and dielectric performance. A Central Composite Design under Response Surface Methodology was used to model tensile, flexural and impact responses and to identify a balanced processing window. Alkali treatment improved fibre–matrix adhesion by removing surface impurities and increasing fibre roughness, which strengthened stress transfer and reduced fibre pull-out. The results show that fibre loading and fibre length strongly affected the measured properties; however, excessive reinforcement or longer fibres reduced performance because of poor dispersion, void formation and local stress concentration. The regression models showed good agreement with the experimental data and were suitable for multi-response optimization within the selected design space. Dielectric measurements indicated acceptable insulating behaviour, particularly in composites with better fibre dispersion and fewer interfacial defects. SEM observations further supported these trends by revealing improved fibre embedding and reduced interfacial gaps in treated composites. Overall, the work shows that alkali treatment, combined with statistical optimization, is a practical route for developing lightweight sisal fibre reinforced polypropylene

Received: 14.07.2026 Accepted: 28.08.2026 Published: 15.09.2026 Issue: 10.2026

Copyright: © 2026 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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