PEER-REVIEWED ARTICLE bioresources.com Acosta et al. (2021). “Guada fiber PU PE composites,” BioResources 16(4), 8049-8059. 8049 Synthesis and Mechanical Behavior of Composite Material Reinforced with Guadua Fiber and with a Polyurethane or Polyester Matrix Ricardo Acosta, a, * Gabriel Calle Trujillo, b and José Luddey Marulanda Arévalo c A reactive hot-melt resin (polyurethane) was used to manufacture Guadua composites with a certain flexibility, high processing speed, good initial rigidity, and high temperature performance. These composites can support a moderate tensile stress, allow for large strains at low stresses, and have a low density and a working temperature range of -40 °C and 110 °C. During the flexural test, bamboo composites with reactive polyurethane matrix do not break or fail during the test. A polyurethane- based reactive hot-melt resin was characterized by tensile tests, Shore hardness tests, differential scanning calorimetry, and thermogravimetry. Besides, a composite material was made with Guadua fiber and polyester matrix, which had a greater strength in the test of tension and flexion, although it had a lower percentage of elongation than the composite material with reactive polyurethane. Guadua fiber can increase the strength by 266% of polyurethane matrix and 228% of polyester matrix. Keywords: Hot melt adhesive; Characterization; Composite material; Guadua fiber Contact information: a: School of Technology, Technological University of Pereira, Pereira, Colombia; b: Mechanical Engineering Faculty, Technological University of Pereira, Pereira, Colombia; c: Mechanical Engineering Faculty, Technological University of Pereira, Pereira, Colombia; * Corresponding author: ricosta@utp.edu.co INTRODUCTION Polymer composite material (PMC) consists of thermoplastic or thermosetting polymer as a matrix with one or more reinforcements, such as carbon, Kevlar, glass, steel, or natural fibers. These composites are used in various industrial applications due to their high specific strength and stiffness, light weight, corrosion resistance, reparability, fatigue resistance, and low cost. PMC can produce good components, as they can be processed conveniently. The mechanical and chemical characteristics of the fibers, matrix, and interface influence in the mechanical properties, besides the way in which the composite deforms and fractures (Andrew et al. 2019: Aruchamy et al. 2020). The most advanced polymer-matrix structural composites are those that involve continuous fibers, such as carbon fibers, which are attractive for their combination of low density, high strength, and high modulus of elasticity (Marulanda et al. 2020). Glass, Kevlar, and carbon fiber reinforced composites do have excellent mechanical properties but are non-renewable, non-ecofriendly, and can cause human health issues. The natural fiber reinforced composites were developed because of their ability to reduce or replace synthetic fibers in many engineering applications (Sharma et al. 2020; Lu et al. 2020). The development of biocomposite materials has attracted considerable interest due to environmental problems and depletion of fossil resources. The combination of natural fiber with polymer matrices (both renewable and non-renewable resources) is called a