Monotonic properties of unidirectional glass fiber (U)/random glass fiber (R)/epoxy hybrid composites

The main objective of the present paper is to study the tensile and bending behaviors of unidirectional glass fiber (U)/random glass fiber (R)/epoxy hybrid composites with total fiber volume fraction (VfT) = 37%. Six kinds of laminated composites of average thickness 5.5 mm were manufactured using hand lay-up technique; i.e. [R]5, [U/R/U/R/U], [U/0.5R/U]S, [0.5R/U/U]S, [U/U/0.5R]S, and [U]5. In bending test, notched and unnotched specimens were tested. For this purpose different circular notch sizes (D = 3, 6, 9 mm) were drilled at the specimen center. Tensile strength, tensile modulus, Poisson’s ratio, bending strength and bending modulus were determined experimentally. The effect of stacking sequences, random fiber relative volume fraction (VfR/VfT), and notch diameter on the mechanical properties of the mentioned composite types were studied. Failure modes of all specimens were investigated.