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| Author(s): |
Francisco Maciel Monticeli
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Guaratinguetá. 2017-08-22. |
| Institution: | Universidade Estadual Paulista (Unesp). Faculdade de Engenharia. Guaratinguetá |
| Defense date: | 2017-07-04 |
| Advisor: | Maria Odila Hilário Cioffi; Sérgio Roberto Montoro |
| Abstract | |
Hybrid composite arose with the aim of reducing high cost materials and, at the same time, maintaining mechanical properties suitable for use. In addition, using different reinforcements, a new material could be obtained which would evidence the advantages of the reinforcements and decrease the disadvantages simultaneously. An important factor, during the processing of polymeric composites for structural application, is the voids formation control, since they act as stress concentrators. The aim of this work was to produce hybrid composites using different stacking of glass and carbon fabrics without significant loss of mechanical properties. For the composite manuftacturing, the preform was initially characterized as the impregnation, for which a general analytical model was developed that determines the permeability parameter of the hybrid composites. In addition, the model was validated by conducting permeability test and the quality of several laminates (hybrid, and non-hybrid) was certified by processing them, and voids were quantified thereof. This project also proposed the improvement of voids analysis by the Hg porosimetry technique with the support of design of experimental. Therefore, it was possible to determine the volumetric fraction of open and closed voids, pore diameter distribution and the distance between voids, in an ensemble analysis with acid digestion and optical microscopy. Carbon preform presented high flow resistance; on the other hand, an opposite behavior was observed for the glass preform. The hybrid architecture presented a positive hybrid effect, which means a synergy that provided a higher permeability value. Therefore, optimization in injection time can be achieved, considering a combination of balanced glass and carbon fabrics. The analytical model was enabled to predict the flow front behavior by showing an overestimated value of 10%. The Hg porosimetry technique was validated for advanced composite voids analysis with similar results obtained by acid digestion techniques and optical microscopy. Based on the results obtained from pore diameter values, which were similar for all composites, it was concluded that this occurs as a function of the type of process and the resin. Although, the distance and the open pores fraction depend directly on the amount of pores along the laminate. Hybrid composites have proven to be a promising material in which it combines the excellent mechanical properties of carbon fiber with the viability of the fiberglass injection cycle. With that, hybrid 2 laminate is the ideal composite for a processing with voids fraction close to the aeronautical use requirement with reduction of high-cost material and processing time. (AU) | |
| FAPESP's process: | 15/19967-4 - Void volume fraction of hybrid composites processed by RTM: optimization of voids determination via mercury porosimetry |
| Grantee: | Francisco Maciel Monticeli |
| Support Opportunities: | Scholarships in Brazil - Master |