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This work aims to evaluate the performance of glass/sisal hybrid composites focusing on mechanical (flexural and impact) and dynamic mechanical analyses (DMTA). Hybrid composites with different fiber loadings and different volume ratios between glass and sisal were studied. The effect of the fiber length has also been investigated. The densities of the composites were compared with the theoretical values, showing agreement with the rule of mixtures. The results obtained in the flexural and impact analysis revealed that, in general, the properties were always higher for higher overall reinforcement content. By DMTA, an increase in the storage and loss modulus was found, as well as a shift to higher values for higher glass loading and overall fiber volume. It was also noticed an increase in the efficiency of the filler and the calculated activation energy for the relaxation process in the glass transition region. The fiber length did not significantly change the results observed in all analyses carried out in this work. The calculated adhesion factor increased for higher glass loadings, meaning the equation may not be applied for the system studied and there are other factors, besides adhesion influencing energy dissipation of the composites.

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In this context, the goal of this work is to study the effect of acetone solvent on the curing process as well as on the properties of epoxy matrices. Thus, acetone/epoxy solutions of different acetone concentrations, namely 0.0, 7.0, 10.0 or 13.0 wt.%, were prepared and then subjected to a mild processing route to remove acetone. Viscosimetric, thermogravimetric, tensile and morphological tests were performed in order to evaluate possible changes in the samples. In addition, Fourier transform infrared spectroscopy (FTIR) analyses were also employed in the search for changes in their molecular structure. Experimental MaterialsThe epoxy resin and the hardener used were araldite GY 251 (diglycidylether of bisphenol A, DGEBA, Huntsmann) and aradur HY 956 (Huntsmann), respectively. Acetone (Quimidrol, 99.5% purity) was the chosen solvent. MethodologyA certain amount of acetone (7.0, 10.0, or 13.0% of the resin weight) was added to the resin and the mixture was simultaneously sonicated in a Sonics Vibration (500 W) and magnetically stirred for an hour. The mixture was then subjected to heating at 50 °C for an hour and conditioned under vacuum for five hours. Finally, hardener was added to the mixture with a 5:1 (w/w) epoxy resin:hardener ratio and homogenized. The curing process took place at room tempera-

This study focused on the mechanical properties of pure sisal, pure glass, and hybrid sisal/glass compression-molded composites, in which various stacking sequences of fiber mat layers were used. It is shown that hybridization originated a material with general intermediate properties between pure glass and pure sisal. However, the importance of controlling the stacking sequence to enhance properties was evident. For instance, to optimize flexural behavior, there must be glass fibers mainly on the top and bottom surfaces. Furthermore, depending on the type of loading and stacking sequence, some hybrid composites may show properties very close to those of pure glass.