MUMBAI, India, May 29 -- Intellectual Property India has published a patent application (202641062215 A) filed by G Ashwin Prabhu; Mr. Sundharesan R; Mr. G. V. Maruthi; Mr. R. Karthikeyan; Dr. T. Albert; Mrs. D. Tharani; Dr. G. Jayanthi; Mr. C. Chelladurai; and Mr. R. Rajeshwaran, Chennai, Tamil Nadu, on May 16, for 'optimization of drilling parameters to minimize delamination in thermoplastic polymer matrix composites for aerospace applications.'
Inventor(s) include Mr. Sundharesan R; Mr. G. V. Maruthi; Mr. R. Karthikeyan; Dr. T. Albert; Mrs. D. Tharani; Dr. G. Jayanthi; Mr. C. Chelladurai; and Mr. R. Rajeshwaran.
The application for the patent was published on May 29, under issue no. 22/2026.
According to the abstract released by the Intellectual Property India: "Delamination is one of the most critical drilling-induced defects in thermoplastic polymer matrix composites used in aerospace structures, as it reduces bearing strength, fatigue life, and dimensional accuracy of fastener holes. This study focuses on the optimization of drilling parameters to minimize delamination in carbon-fiber-reinforced thermoplastic composites. Three major drilling parameters-spindle speed, feed rate, and drill point angle-were considered at practical aerospace machining ranges of 3000-9000 rpm, 0.03-0.12 mm/rev, and 90-135, respectively. Delamination was evaluated using the delamination factor, defined as the ratio of maximum damaged diameter to nominal hole diameter. Experimental trends indicated that feed rate had the strongest influence on delamination because higher feed increases thrust force and promotes interlaminar crack propagation. When feed rate increased from 0.03 mm/rev to 0.12 mm/rev, thrust force rose from approximately 48 N to 126 N, and the delamination factor increased from 1.08 to 1.34. Increasing spindle speed from 3000 rpm to 7000 rpm reduced delamination by nearly 14-18%, mainly due to improved cutting continuity and reduced chip load per revolution. However, speeds above 8000 rpm showed marginal improvement because excessive heat softened the thermoplastic matrix, causing fiber pull-out and hole wall smearing. The optimum drilling condition was found at 7000 rpm spindle speed, 0.04 mm/rev feed rate, and 118 drill point angle, producing a minimum delamination factor of 1.06 and an average thrust force of 52 N. Compared with the least favorable condition of 3000 rpm, 0.12 mm/rev, and 135, the optimized setting reduced delamination by approximately 24% and thrust force by 58%. These results justify the selection of moderate-to-high spindle speed and low feed rate for aerospace composite drilling, as they balance machining quality, thermal stability, and structural integrity of the drilled holes."
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