*Communication* **Ubim Fiber (***Geonoma baculífera***): A Less Known Brazilian Amazon Natural Fiber for Engineering Applications**

**Belayne Zanini Marchi 1,\*, Michelle Souza Oliveira <sup>1</sup> , Wendell Bruno Almeida Bezerra <sup>1</sup> , Talita Gama de Sousa <sup>1</sup> , Verônica Scarpini Candido <sup>2</sup> , Alisson Clay Rios da Silva <sup>2</sup> and Sergio Neves Monteiro <sup>1</sup>**


**Abstract:** The production of synthetic materials generally uses non-renewable forms of energy, which are highly polluting. This is driving the search for natural materials that offer properties similar to synthetic ones. In particular, the use of natural lignocellulosic fibers (NLFs) has been investigated since the end of 20th century, and is emerging strongly as an alternative to replace synthetic components and reinforce composite materials for engineering applications. NLFs stand out in general as they are biodegradable, non-polluting, have comparatively less CO<sup>2</sup> emission and are more economically viable. Furthermore, they are lighter and cheaper than synthetic fibers, and are a possible replacement as composite reinforcement with similar mechanical properties. In the present work, a less known NLF from the Amazon region, the ubim fiber (*Geonoma bacculifera*), was for the first time physically characterized by X-ray diffraction (XRD). Fiber density was statistically analyzed by the Weibull method. Using both the geometric method and the Archimedes' technique, it was found that ubim fiber has one of the lowest densities, 0.70–0.73 g/cm<sup>3</sup> , for NLFs already reported in the literature. Excluding the porosity, however, the absolute density measured by pycnometry was relatively higher. In addition, the crystallinity index, of 83%, microfibril angle, of 7.42–7.49◦ , and ubim fiber microstructure of lumen and channel pores were also characterized by scanning electron microscopy. These preliminary results indicate a promising application of ubim fiber as eco-friendly reinforcement of civil construction composite material.

**Keywords:** ubim fiber; natural lignocellulosic fiber; X-ray diffraction; density; morphology characterization
