Influence of Spindle Speed on Drilling‐Induced Delamination and Hole Quality in <scp>3D</scp> ‐Printed <scp>ONYX</scp> /Glass Fiber Composite Laminates: An Experimental and <scp>FEA</scp> Approach

ABSTRACT This Paper quantifies how spindle speed governs delamination and hole quality when drilling additively manufactured ONYX/glass‐fiber laminates—an area underexplored relative to conventionally made composites. Drilling tests at 500, 800, 1250, and 1850 rpm with a constant feed of 0.05 mm/rev assessed delamination factor, circularity, roundness error, and surface roughness. Increasing spindle speed systematically lowered thrust force and delamination, yielding smoother, more accurate holes. An orthotropic FEA model in ANSYS with Hashin failure criteria reproduced the stress fields and damage initiation observed experimentally, showing strong agreement ( R 2 = 0.962). Scale‐calibrated SEM quantified damage modes (fiber pull‐out, matrix cracking, and interlaminar separation) and confirmed the reduced damage at higher speeds. A curve‐fitted predictive relation between spindle speed and delamination factor was established, providing a practical process‐selection tool. These results demonstrate that spindle speed is inversely related to delamination in 3D‐printed ONYX/glass‐fiber laminates and offer validated guidelines to improve machinability and structural reliability of additively manufactured components for aerospace, drone, and automotive applications.