A New Experimental Framework for Unsupported Drilling of Thin Woven GFRP Laminates

High-quality drilled holes are critical in thin fabric-reinforced composites used in many industrial applications; however, the influence of woven architecture on drilling performance without a backup plate remains insufficiently defined. This paper introduces the first comprehensive experimental and statistical framework for evaluating unsupported drilling of thin woven glass fiber-reinforced polymer (GFRP) laminates. The framework integrates the effect of support opening width, fiber weight fraction (wf), feed per tooth, and fabric architecture to quantify their combined effects on delamination, cutting forces, and surface roughness. The samples consisted of vacuum mold-pressed GFRP laminates. Drilling tests were conducted on plain and twill-woven plates, and hole quality was evaluated using thrust force, delamination factor, and surface roughness (Sa). A statistical DOE and multifactorial ANOVA were applied to quantify the effects of the main parameters. For plain-woven GFRP, the best results were obtained with a 65 mm support opening width, 45% fiber wf, and 0.04 mm/tooth feed. Plain-woven laminates exhibited lower average surface roughness (Sa ≈ 5.0–6.5 µm) than twill-woven laminates (Sa ≈ 6.0–7.0 µm). The study demonstrates how fabric architecture and drilling parameters jointly influence hole quality in thin GFRP composites, providing practical guidance for manufacturing applications.