Effect of fiber separation degree on the properties of bamboo fiber composites

The steam explosion is an economical and effective method for obtaining bamboo fibers (BFs). However, little attention has been paid to the differences in the separation forms of steam-exploded fibers, which may affect their application in the field of composites. In this study, the steam-exploded fibers were classified into five categories (BF-1 to BF-5) according to their degree of separation (from low to high). The effects of different bamboo fibers on the structure and properties of bamboo fiber composites (BFCs) were investigated using scanning electron microscopy, physical properties testing, flexural testing, internal bonding testing, and dynamic mechanical analysis. The results indicated that the fibers separated from bundles into single fibers with progressively smaller diameters as the degree of separation increased. Higher degrees of fiber separation produced composites that had better water resistance performances. The water absorption of composites made with BF-5 was 15.02% lower than that of composites made with BF-2. An excessively low or high separation degree negatively affected the mechanical properties and interfacial bonding properties of the BFC. Composites made with BF-4 had the highest flexural properties and fiber/matrix interfacial bonding, with a flexural strength, flexural modulus, and energy storage modulus that reached 102 MPa, 6970 MPa, and 5412 MPa, respectively. Fiber separation degree is a key factor influencing the properties of composites. When preparing composites with enhanced performance using the steam explosion method, fibers with a moderate degree of separation should be prioritized.