The substitution of natural fibers for synthetic ones as reinforcement of polymer matrix composites is today not only the subject of investigation but also engineering applications. Natural fibers display environmental advantages in association with economic benefits related to comparatively lower cost as well as less energy consumption. Several natural lignocellulosic fibers (LCF's) extracted from worldwide cultivated plants, such as sisal, coir, cotton, flax, among others, are successfully being used in composites. A great number of other LCF's, especially from wood species, has a reinforcement potential waiting to be explored. Thus, the objective of this short communication is to evaluate the thermogravimetric (TG/DTG) behavior of polyester matrix composites reinforced with relatively higher volume fractions, 30, 40 and 50 vol%, of eucalyptus fibers. The incorporation of eucalyptus fibers slightly reduces the thermal stability of the polyester matrix by a small decrease in the onset of thermal degradation and the DTG peak temperature as compared to neat polyester. The limit for practical application of these composites could be set as 300 °C, before the onset of major weight loss. Keywords: Eucalyptus fiber, Polyester composites, Thermogravimetry, TG/DTG test

This study investigates the differences in mechanical properties between acrylonitrile butadiene styrene (ABS) samples produced using fused deposition modeling (FDM) and stereolithography (SLA) using ABS filaments and ABS-like resin, respectively. The central question is to determine how these distinct printing techniques affect the properties of ABS and ABS-like resin and which method delivers superior performance for specific applications, particularly in dental treatments. The evaluation methods used in this study included Shore D hardness, accelerated aging, tensile testing, Izod impact testing, flexural resistance measured by a 3-point bending test, and compression testing. Poisson’s ratio was also assessed, along with microstructure characterization, density measurement, confocal microscopy, dilatometry, wettability, Fourier-transform infrared spectroscopy (FTIR), and nanoindentation. It was concluded that ABS has the same hardness in both manufacturing methods; however, the FDM process results in significantly superior mechanical properties compared to SLA. Microscopy demonstrates a more accurate sample geometry when fabricated with SLA. It is also concluded that printable ABS is suitable for applications in dentistry to fabricate models and surgical guides using the SLA and FDM methods, as well as facial protectors for sports using the FDM method.

Engineering activities aim to satisfy the demands of society. Not only should the economic and technological aspects be considered, but also the socio-environmental impact. In this sense, the development of composites with the incorporation of waste has been highlighted, aiming not only for better and/or cheaper materials, but also optimizing the use of natural resources. To obtain better results using industrial agro waste, we need to treat this waste to incorporate engineered composites and obtain the optimal results for each application desired. The objective of this work is to compare the effect of processing coconut husk particulates on the mechanical and thermal behavior of epoxy matrix composites, since we will need a smooth composite in the near future to be applied by brushes and sprayers with a high quality surface finish. This processing was carried out in a ball mill for 24 h. The matrix was a Bisphenol A diglycidyl ether (DGEBA)/triethylenetetramine (TETA) epoxy system. The tests that were performed were resistance to impact and compression, as well as the linear expansion test. Through this work, it can be observed that the processing of coconut husk powder was beneficial, allowing not only positive improvements to the properties of the composite, but also a better workability and wettability of the particulates, which was attributed to the change in the average size and shape of particulates. That means that the composites with processed coconut husk powders have improved impact strength (46 up to 51%) and compressive strength (88 up to 334%), in comparison with unprocessed particles.

Environmental aspects and economical advantages are motivating the use of natural fiber as reinforcement of polymer composites in substitution for synthetic fiber composites such as fiber glass. In particular, the sisal fiber is one of the most investigated and being used in engineering systems. By contrast to synthetic fibers, natural fibers have the disadvantage of being heterogeneous in their dimensions specially the diameter. In several natural fibers it has been found that the smaller the diameter, the stronger is the fiber. In this work a Weibull analysis of sisal fibers tensile strength was performed to find a correlation with the diameter. The results revealed an inverse dependence of the tensile strength with the diameter. The observation of ruptured fibers by scanning electron microscopy suggested possible mechanisms that justify a hyperbolic correlation.

The search for new greener materials that contribute to a more sustainable world motivated the present study in which novel biocomposites with 10, 20 and 30 vol% of piassava fiber powder waste reinforcing castor oil-based polyurethane (COPU) intended for a high-performance coated floor (HPCF) were developed. The novel biocomposites were characterized by flexural, Izod impact and wear standard tests as well as Fourier transform infrared spectroscopy (FTIR) and fracture analysis using scanning electron microscopy (SEM). Both flexural modulus and strength displayed marked increases reaching more than 800 and 500%, respectively, compared to plain COPU for 30 vol% piassava powder incorporation. FTIR bands indicated the existence of interaction between the piassava constituents and COPU. However, SEM fractographs disclosed the presence of bubbles attributed to retained gases during the COPU curing. Consequently, the Izod impact resistance showed a 50% decrease while the wear was more than three times accentuated for 30 vol% piassava powder biocomposite. These results met the specified values of corresponding standards and revealed a promising new greener material for HPCFs.