Efeitos das condições de processamento nas propriedades viscoelásticas e na capacidade de absorção de energia de compósitos laminados

Abstract

Specific energy absorption capability (ES) of polymer matrix composite materials has been a topic of great interest due to their potential to be tailored to improve protection to passengers in vehicles and aircrafts in case of accidents. This property has been related to fiber and matrix properties, fiber orientation, volume fraction of constituent phases, laminae orientation, geometry of the samples, the presence of trigger mechanisms and loading speed. In this research, the effects of processing conditions (with or without vacuum) on the specific energy absorption capacity and on the viscoelastic properties of polymer composites were investigated. Tubes were fabricated using plain weave E-glass fabric (0/90) and three types of resin: epoxy, polyester and vinyl ester. Tubes were produced by mandrel wrapping and the influence of the application of vacuum during processing on the composite properties was investigated. Compression tests were carried out for the determination of the specific energy absorption capability. Dynamic mechanical analysis was also used to perform viscoelastic characterization of the composites. Test results indicated that vacuum processing produced an increment on storage modulus (E’), which was related to an increase in fiber volume fraction. The corresponding decrease in matrix volume fraction reduced the interlaminar strength and increased energy dissipation, thus increasing the loss modulus (E”). A relation between vacuum processing and a reduction in the intensity of the tan d peak was also verified. It was also observed that the reduction in interlaminar strength facilitated interlaminar crack growth, thus reducing ES. Changes in specific energy absorption capability associated with vacuum processing were related to alterations on the material viscoelastic parameters. Ultimately, this work assessed the feasibility of the use of dynamic mechanical analysis as a tool for the development and process related quality control of materials for crashworthiness applications.