Characteristics of the shear mechanical properties and the influence mechanism of short basalt fiber reinforced polymer composite materials

To increase the engineering applications of basalt fiber, the characteristics of the shear mechanical properties and the influence mechanisms of the fiber length ( L _f ) and volume fraction ( V _f ) for short basalt fiber reinforced epoxy resin polymer composites were investigated. The following results were obtained: (1) The first critical loads on all the shear load–displacement curves are close to the same value due to having the same interface bonding of the fiber–matrix; (2) the shear strength, deformation, and energy dissipation capacity all increase with increasing V _f ; however, when L _f is 6 or 9 mm, these increases are slower, whereas when L _f is 3 mm, these values increase at an approximately constant rate; and (3) the shear elastic modulus of the samples reaches its maximum value when L _f is 3 mm and V _f is 25%; however, it increases more quickly when L _f is 6 or 9 mm. The failure mode of the samples with the larger L _f values is mainly debonding between the fiber and matrix; when V _f is high, the fibers can easily bundle, which reduces the adhesion between the fibers and matrix. In addition, the main failure mode of the 3-mm-long fiber samples is fiber pull-out; when V _f is high, the short fibers that are not pulled out significantly increase the deformation ability.