Lightweight hybrid polyester composites reinforced with Luffa cylindrica and glass fiber mats

The use of sustainable and ecological materials in the development of new products has led to an increase in research projects focused on the total or partial replacement of synthetic reinforcements with vegetable fibers in composites. This study proposes applying layers of vegetable sponge (Luffa cylindrica) together with a random glass fiber mat (FG) to produce hybrid composites with a polyester matrix, aiming to determine their physical and mechanical properties, including their density, moisture content, water absorption, thickness swelling, tensile strength, flexural strength, and Rockwell hardness. The composites were manufactured by cold pressing in a closed mold. The vegetable sponge (Luffa cylindrica) and a random glass fiber mat were arranged by varying the quantities and positions of the central and outer layers in the composites. The results showed that reinforcing the vegetable sponge (Luffa cylindrica) decreased the density of all hybrid composites, with the lowest value of 1.12 g × cm−3 observed for the configuration with sponges on the outside (90°/FG/90°). In the flexural strength test, the hybrid composite reinforced with vegetable sponge (Luffa cylindrica) in the center (FG/90°/FG) showed the highest stress and stiffness values, at 91.8 MPa and 3704.9 MPa, respectively. In the Rockwell hardness tests, the hybrid treatment reinforced with fibers in the (FG/90°/FG) configuration showed the highest value among the hybrid and natural treatments, with a value of 104.7 HHR (Rockwell R Hardness). The results showed that the reinforcement and layer position of the vegetable sponge (Luffa cylindrica) and the random glass fiber mat significantly influenced the physical and mechanical properties of the manufactured composites. These characteristics demonstrate that hybridization between layers of synthetic and natural fibers can produce materials with distinct properties from the same constituents. The hybrid composites also exhibited light weight, reduced economic costs of obtaining and processing, reduced synthetic constituents, and good physical and mechanical properties, in addition to being natural, biodegradable, and renewable.