Experimental Investigation on Optimized Ultrasonic Welding of Sisal Natural Fiber‐Reinforced <scp>HDPE</scp> Polymer Composites

ABSTRACT Materials play a pivotal role in technological advancements, and the development of sustainable materials is a key focus for researchers seeking to promote environmental sustainability and optimal resource utilization. Natural fiber‐reinforced composites represent a promising class of materials with significant potential for engineering applications, including automotive, construction, and household goods. In this study, woven mat sisal fiber‐reinforced high‐density polyethylene (HDPE) composites were fabricated using compression molding. Joining these composites is essential for creating complex product designs and ultrasonic welding (USW) a solid‐state fusion bonding technique was employed due to its efficiency in welding thermoplastics. USW utilizes high‐frequency ultrasonic vibrations combined with applied force to generate frictional heat at the mating surfaces, facilitating bonding. This experimental investigation examines the USW behavior of sisal/HDPE composites, focusing on process optimization to determine the optimal welding parameters for superior joint strength and weld quality. The mechanical performance of the welded joints was evaluated through failure load and tensile strength measurements. Postfailure analysis included thermal behavior assessment, crystallinity degree evaluation, and scanning electron microscopy (SEM) to elucidate the fracture mechanisms under tensile loading. The findings contribute to a deeper understanding of USW for natural fiber‐reinforced thermoplastic composites, supporting their broader industrial adoption.