A study was undertaken to investigate the tensile, bending, effect and delamination failing of boiled composites by strengthening chemical treated bananas and coir fibres into polylactic acid (NaOH solution treatment), as untreated (PLA). The composites were produced by using the fibres extracted through retting and manual processes. The composites are produced with 25, 30 and 35% fibres for both treated and untreated fibres. Banana-coir fibres have been treated at room temperature with 4 percent NaOH solution. After boiling and comparison with one another, these composites are tested for delamination and tensile, bending and impact strength. The drilling process was performed at different speed levels and feed rate as the response to its input parameter and delamination failure. In order to influence fibre contents and drilling parameters (chemical fibre, cutting speed, feed rate) on delamination, tensile, bending and impact strength for various fiber-reinforced composites, the Taguchi technique with L9 (34) Orthogonal array was chosen. The results show that the failure to delamine chemically treated banana coir fiber-PLA enhanced compounds during the boiling process is heavily influenced by the lower fibre, increased feed rate, and lower spindle rate. © 2023 Elsevier B.V., All rights reserved.