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- Drilling damage in composite materialPublication . Durão, Luís M.; Tavares, João Manuel R. S.; Albuquerque, Victor Hugo C. de; Marques, Jorge Filipe Simões; Andrade, Óscar Nicolau GomesThe characteristics of carbon fibre reinforced laminates have widened their use from aerospace to domestic appliances, and new possibilities for their usage emerge almost daily. In many of the possible applications, the laminates need to be drilled for assembly purposes. It is known that a drilling process that reduces the drill thrust force can decrease the risk of delamination. In this work, damage assessment methods based on data extracted from radiographic images are compared and correlated with mechanical test results—bearing test and delamination onset test—and analytical models. The results demonstrate the importance of an adequate selection of drilling tools and machining parameters to extend the life cycle of these laminates as a consequence of enhanced reliability.
- 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.