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- Drilling tool geometry evaluation for reinforced composite laminatesPublication . Durão, Luís M.; Gonçalves, Daniel J. S.; Tavares, João Manuel R. S.; Albuquerque, Victor Hugo C. de; Vieira, A. Aguiar; Marques, A. T.In this work, a comparative study on different drill point geometries and feed rate for composite laminates drilling is presented. For this goal, thrust force monitoring during drilling, hole wall roughness measurement and delamination extension assessment after drilling is accomplished. Delamination is evaluated using enhanced radiography combined with a dedicated computational platform that integrates algorithms of image processing and analysis. An experimental procedure was planned and consequences were evaluated. Results show that a cautious combination of the factors involved, like drill tip geometry or feed rate, can promote the reduction of delamination damage.
- Tool effects on hybrid laminates drillingPublication . Durão, Luís M.; Tavares, João Manuel R. S.; Albuquerque, Victor Hugo C. de; Marques, A. T.; Magalhães, A. G.; Vieira, A. AguiarFiber reinforced plastics are increasing their importance as one of the most interesting groups of material on account of their low weight, high strength, and stiffness. To obtain good quality holes, it is important to identify the type of material, ply stacking sequence, and fiber orientation. In this article, the drilling of quasi-isotropic hybrid carbon +glass/epoxy plates is analyzed. Two commercial drills and a special step drill are compared considering the thrust force and delamination extension. Results suggest that the proposed step drill can be a suitable option in laminate drilling.
- Damage analysis of carbon/epoxy plates after drillingPublication . Durão, Luís M.; Tavares, João Manuel R. S.; Magalhães, A. G.; Marques, A. T.; Baptista, A. P. M.Drilling of composites plates normally uses traditional techniques but damage risk is high. NDT use is important. Damage in a carbon/epoxy plate is evaluated by enhanced X-rays. Four different drills are used. The images are analysed using Computational Vision techniques. Surface roughness is compared. Results suggest strategies for delamination reduction.