The aim of this study was to investigate the mechanical and thermal properties of composite pipes based on epoxy resin and glass fibers produced by filament winding (FW) technology. Epoxy resins are widely used polymers in FW composite structures. The thermal characterization of the neat epoxy resin, curing, and post-curing characteristics for the determination of polymerization and glass transition temperature was performed, which is important for the mechanical properties of polymer composite pipes. In the present work, the applicability of the full factorial experimental design in predicting the hoop tensile and compressive strengths of glass fiber/epoxy resin composite pipes was investigated. The composite pipes in accordance with the 2³ full factorial experimental design by using of three parameters and two levels of variation were prepared. The winding speed of the composites was taken to be the first factor, the second was the fiber tension, and the third was winding angle. To approximate the response, i.e., the mechanical properties of the composite pipes within the study domain, the first-order linear model with the interaction was used. The influence of each individual factor to the response function was established, as well as the influence of the interaction of the two and three factors. Additionally, those results were completed with the thermal characterization of the polymer composite pipes. From received results from mechanical and thermal characterization, it was concluded that the properties of composite specimens were highly affected by the analyzed parameters in filament winding technology. It was found that the estimated first-degree regression equation with the interaction gave a very good approximation of the experimental results of the hoop tensile and the compressive strengths of composite pipes within the study domain.

Article Preparation and Characterization of PoIy(lactic acid)/Rice Hulls based Biodegradable Composites was published on October 1, 2008 in the journal Journal of Polymer Engineering (volume 28, issue 6-7).

Renewable raw materials and recyclable thermoplastic polymers provide attractive eco-friendly quality as well as environmental sustainability to the resulting natural fiber reinforced composites. We studied the possibility of using the recycled polypropylene (PP) for production of composites based on kenaf fibers (KF) and rice hulls (RH) as reinforcements. Polypropylene/rice-hulls (PP/RH/CA) and polypropylene/kenaf (PP/K/CA) composites with 30% fiber (filler) content and appropriate compatibilizing agent (CA)—a maleic anhydride grafted PP (MAPP), have been prepared by two steps procedure: melt mixing and compression molding. Flexural strength and thermal stability of the composites with recycled PP were similar to those with neat PP. The composites reinforced with kenaf fibers have shown better properties than those based on rice hulls. The flexural strength of the composite sample with recycled PP is 51.3 MPa in comparison with 51.1 MPa for the composite with neat PP. Degradation temperatures of neat and composite with recycled PP at residual weight 90% are 344.4°C and 343.5°C, respectively. The results obtained report the possibility of utilization of recycled PP for the production of natural reinforcements based composites with good mechanical characteristics for using as construction building materials in housing systems.

The interest in natural fiber-reinforced polymer composites is growing rapidly due to their high performance in terms of mechanical properties, significant processing advantages, excellent chemical resistance, low cost and low density. In this study, the compression and injection molding of polypropylene (PP) and polylactic acid (PLA) based composites reinforced with rice hulls or kenaf fibers was carried out and their basic properties were examined. Rice hulls from rice processing plants and natural lignocellulosic kenaf fibers from the bast of the plant Hibiscus Cannabinus represent renewable sources that could be utilized for composites. Maleic anhydride grafted PP (MAPP) and maleic anhydride grafted PLA (MAPLA) were used as coupling agents (CA) to improve the compatibility and adhesion between the fibers and the matrix. Composites containing 30 wt % reinforcement were manufactured by compression and injection molding, and their mechanical and thermal properties were compared. It was found that the techniques applied for manufacturing of the eco-composites under certain processing conditions did not induce significant changes of the mechanical properties. The flexural strength of the compressed composite sample based on PP and kenaf is 51. 3 MPa in comparison with 46.7 MPa for the same composite produced by injection molding technique. Particularly, PP-based composites were less sensitive to processing cycles than PLA-based composites. The experimental results suggest that the compression and injection molding are promising techniques for processing of eco-composites. Moreover, the PP-based composites and PLA-based composites can be processed by compression and injection molding. Both composites are suitable for applications as construction materials.

In this study, rice-hull-filled poly(lactic acid) (PLA) biocomposites were prepared through the addition of 5 wt.% PLA-grafted-MA (CA) for the enhancement of adhesion between the polymer matrix and natural filler. The composites containing 30 wt.% rice hulls (RH) were prepared by compression molding, with particular attention given to the introduction of recycled PLA matrix, as well as to the possibility of the recycling and reuse of PLA/RH biocomposites. For all biocomposites, produced from neat polymer and RH and those produced after the recycling of PLA/RH composites, the mechanical and thermal properties were analyzed and compared to those of a commonly used thermoplastic based-polymer, polypropylene (PP), containing the same reinforcement. Thermal stability of biocomposites based on recycled PLA matrix and of the new composites produced from recycled ones was practically unchanged. Introduction of the recycled PLA matrix into biocomposites resulted in decreased flexural modulus and strengths of about 50%. Utilization of the mixture obtained after the thermal-mechanical recycling of the whole biocomposite resulted in a composite with slightly increased flexural modulus and decreased flexural strength.The obtained results have shown that rice-hull-filled poly(lactic acid) biocomposites could be recycled and utilized for the production of new eco-materials with acceptable thermal and mechanical properties. Namely, the results for flexural strength and modulus of the recycled biocomposite samples are comparable to those of conventional formaldehyde wood medium density fiberboards used as construction elements for indoor applications. Keywords: biocomposites, polylactic acid, polypropylene, rice hulls, compression moulding.

The aim of this study is to investigate the mechanical properties of continuous glass fiber reinforced composite tubes produced by filament winding technique with three different winding angles. With help of split-disk tests hoop tensile properties of selected specimens were determined, where reliable results were obtained with low standard deviations. It was observed that bigger winding angle lead to higher hoop tensile properties of filament wound tubular samples. Also, the effect of reinforcement direction on the mechanical performances of these composites has been presented. Fiber fracture and fiber-matrix debonding is observed to be the dominant failure mechanisms by samples winded with bigger winding angles, whereas delamination in addition to these mechanisms is detected by samples with smaller winding angles. From received results it is concluded that, mechanical properties of composite specimens are depended from winding angles in filament winding technology.With help of conducted SEM analysis good merger between glass fibers and the epoxy matrix was seen, but cracks within plies and broken fiber were noticed, due to the high fiber branching.