Clarissa Coussirat Angrizani

Short beam strength of curaua, sisal, glass and hybrid composites

In this study, the short beam strength characteristics of randomly oriented composites were comprehensively investigated. The following parameters were varied: fiber used (curaua or sisal), fiber washing or surface chemical treatment with sodium hydroxide/sodium borohydride, fiber length (from 5 to 60 mm), hybridization with glass fiber and the pre-processing of the polyester resin. The overall fiber volume fraction was kept constant (30 vol.%). In all configurations, the composites containing curaua fiber obtained higher short beam strength than those with sisal. An increase in fiber length yielded higher short beam strength. The optical and electronic micrographs showed mostly horizontal cracks, typical of shear failure. In addition, it was carried out a study of the ASTM D2344 standard regarding the span-to-thickness ratio recommended for testing, the measured strength decreased for higher span-to-thickness ratio for specimens with higher length and width, and the failure mode changed to bending around span-to-thickness >12.

Analysis of curaua/glass hybrid interlayer laminates

This study compares the mechanical properties of curaua, glass and hybrid curaua/glass laminates evaluated experimentally with those obtained theoretically using commercial software for composites. Hybrids laminates were produced varying the fiber layer stacking sequence with the aim of optimizing the combination of vegetable and synthetic fibers. Composites were compression molded using eight layers of glass and/or curaua fiber mats and mechanically tested as per ASTM standards. The combination of curaua and glass fibers produced a material with intermediate properties and, depending on the type of mechanical loading and the stacking sequence, some hybrids showed properties close to the pure glass fiber composites. Furthermore, hybrid composites with glass layers closer to the surfaces showed the best overall results.

Obtenção e Caracterização de Compósitos Utilizando Poliestireno como Matriz e Resíduos de Fibras de Algodão da Indústria Têxtil como Reforço

The aim of this work is to use cotton fibers as reinforcement in polymeric composites materials using polystyrene as matrix and poly(styrene-co-maleic anhydride) coupling agent. The composites were developed by first mixing in a single screw extruder and a co-rotation parallel twin screw extruder and injection molded. The composites were characterized by analysis mechanical, thermal, dynamic mechanical thermal and morphology. The results from the flexural and tensile strength demonstrate that the addition of 20% cotton fibers tends to increase in these properties; however there is increase when using a coupling agent. The impact resistance increased with the increase of load; however the results of the composites with coupling agent were lower than those without. The temperature of thermal deflection increased for all composites, but the increase for the composites with 20% cotton fiber was approximately 7 oC. The results show that the addition of cotton fibers changes the initial temperature of wheight loss for the composites to temperatures close to 200 oC. The DMTA analysis showed increasing in stiffness and the storage modulus with cotton addition. The micrographs showed a reduction in the pull-out fibers, due to a greater adhesion fiber / matrix with the use of compatibilizer.

Influence of stacking sequence on the mechanical and dynamic mechanical properties of cotton/glass fiber reinforced polyester composites

This study focuses on the use of waste cotton fiber from the textile industry to produce composites with unsaturated polyester and to evaluate the performance of glass (G) / cotton (C) fiber laminates, particularly their mechanical and dynamic mechanical properties. Distinct stacking sequences were studied but the overall fiber content was kept constant. In general, hybrid laminates exhibited intermediate mechanical properties compared to those of the pure laminates, and optimum performance was obtained when the glass fiber mats were placed on the surfaces of the composite. Furthermore, some hybrid laminates exhibited superior dynamic mechanical performance, even compared to the pure glass laminate. Lower tan delta peak height (related to better fiber-matrix interaction) values and higher Tg were reported for the [C/G/ G ¯]s and [G/C/ C ¯]s samples which, together with the [G/C/ G ¯]s sample, exhibited the best results for reinforcement effectiveness and loss modulus peak height. Therefore, it is found possible to partially replace the glass fiber by waste cotton fiber considering that the final product may be optimized for mechanical property, which requires glass fiber at the surface of the laminate, or for dynamic mechanical properties, that allows higher cotton fiber content.

Thermal and Mechanical Investigation of Interlaminate Glass/Curaua Hybrid Polymer Composites

ABSTRACT The combination of synthetic and vegetable fibers in a polyester matrix can produce a hybrid material that may substitute pure glass composites depending on the application. Analysis of their dynamical mechanical properties is important, enabling a better understanding of the structure/property relationship. In this context, various curaua (C) /glass (G) interlaminar hybrid composites were hot compress molded with an overall fiber loading of 30 vol.% and a volume ratio of 1:1 with the aim of studying the influence of the fiber stacking sequence on their thermal, mechanical, and dynamic mechanical properties. Higher hardness was observed when glass fiber was near the surface being tested, and the presence of two consecutive glass layers yielded competitive impact properties in comparison with pure glass composite. In the dynamic mechanical analysis, highest storage modulus values were obtained for the pure glass composite, followed by [G2/C2]s, whereas pure curaua yielded the lowest values. Higher dissipation energy was also found for the [G2/C2]s composite, attributed to the four curaua layers grouped near the mid-plane. The higher glass transition temperature and the largest tan delta peak height and peak width at half-height was found for the pure glass composite.