Fernando Eduardo Macedo Cunha

Excellent bonding behaviour of novel surface-tailored fibre composite rods with cementitious matrix

Novel composite rods were produced by a special braiding technique that involves braiding of polyester yarns around a core of resin-impregnated carbon fibres and subsequent curing. The surface roughness of these braided rods was tailored by replacing one or two simple yarns in the outer-braided layer with braided yarns (produced from 8 simple yarns) and adjusting the take-up velocity. Pull-out tests were carried out to characterize the bond behaviour of these composite rods with cementitious matrix. It was observed that the rod produced with two braided yarns in the outer cover and highest take-up speed was ruptured completely before pull-out, leading to full utilization of its tensile strength, and exhibited 134% higher pull-out force as compared to the rods produced using only simple braiding yarns.

Acoustical behavior of hybrid composite sandwich panels

This paper deals with the characterization of acoustic insulation behaviour of hybridsandwich composite panels for application in modular house construction. These sandwich panelsare a sustainable, light-weight and durable solution, since are based on natural fibers structureimpregnated with a thermosetting polymer. In this way, three different types of hybrid compositepanels containing polyurethane core and laminated composite skins were produced and analyzed,varying the composition of laminates. The composite laminates of the prototypes were producedusing a vacuum infusion technique and were composed of glass and jute fibers, impregnated with apolyester resin. The solutions developed were compared with a standard, composed of plasterboardshaving different thicknesses and used for thermal and acoustic insulation. Acoustic insulationcharacterization was performed on specimens with 220x220 mm size in a sound proof acousticchamber. The tested sandwich panels showed promising results; however, their overall performancewas lower as compared to the performance of standard solutions used for comparison. Nevertheless,the specific acoustic insulation performance, i.e. sound reduction per unit mass of material for thedeveloped sandwich panels was significantly higher as compared to the standard materials,indicating better suitability of this innovative solution for light-weight construction and modularhousing.

Study of the potential employment of Malvaceae Species in composites materials

The employ of vegetal fibers for textiles and composites represents a great potential in economic and social sustainable development. Some Malvaceae species are considered tropical cosmopolitans, such as from Sida genus. Several species of this genus provide excellent textile bast fibers, which are very similar in qualities to the jute textile fiber. The objective of the present study is present the physicochemical characterization of six Brazilian vegetal fibers: Sida rhombifolia L.; Sida carpinifolia L. f.; Sidastrum paniculatum (L.) Fryxell; Sida cordifolia L.; Malvastrum coromandelianum (L.) Gurck; Wissadula subpeltata (Kuntze) R.E.Fries. Respectively the two first species are from Brazilian Atlantic Forest biome and the four remaining from Brazilian Cerrado biome, despite of present in other regions of the planet. The stems of these species were retted in water at 37oC for 20 days. The fibers were tested in order to determine tensile rupture strength, tenacity, elongation, Young’s modulus, cross microscopic structure, Scanning Electronic Microscopy (SEM), regain, combustion, acid, alkali, organic solvent and cellulase effects, pH of the aqueous extract, Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The obtained values were compared with those from fibers of recognized applicability in the textile industry including hemp. The results are promising in terms of their employment in thermoset and thermoplastic medium resistance composites.