Multi-factorial analysis and optimization of delamination damage parameters in the drilling of woven ramie/epoxy resin composite

Abstract

The growing demand for lightweight and eco-friendly materials has accelerated the use of natural fiber composites in structural applications. However, drilling-induced delamination remains a significant challenge in machining. This study investigates the influence of drilling parameters on the delamination behavior of woven ramie/epoxy resin composites using a TPR 1100 drilling machine. TPR is the model designation of the pillar-drilling machine used in the experiments. The composite was fabricated from S-type 12/3 woven ramie fiber reinforced with epoxy resin and a polyaminoamide hardener (60:40 ratio). Delamination was quantified using 2400 DPI macrophotography and analyzed with Image-Pro Plus v4.5 software. Four process parameters, namely number of layers (3, 4, and 5), drill bit diameter (6, 8, and 10 mm), spindle speed (88, 455, and 1500 rpm), and feed rate (0.05, 0.09, and 0.15 mm/rev) were optimized using the Taguchi method, with analysis of variance used to assess parameter significance. The results showed that drill bit diameter was the dominant factor influencing delamination (entry: 70.1%; exit: 44.8%), followed by the number of layers and spindle speed, while feed rate had the least effect. The optimal parameter combination (3 layers, 6 mm drill, 88 rpm spindle speed, and 0.09 mm/rev feed) reduced delamination by 7.87% at the entry side and 10.42% at the exit side. These findings provide practical guidelines for minimizing structural degradation during machining, thereby extending the mechanical reliability of ramie/epoxy composites. The outcomes are directly applicable to the automotive, construction, and sustainable product manufacturing sectors, advancing eco-friendly machining standards and providing significant benefits for future industrial applications.

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