In-plane shear properties of unidirectional glass fiber (U)/random glass fiber (R)/epoxy hybrid and non-hybrid composites

The in-plane shear properties (shear strength τxy and shear modulus Gxy) of unidirectional glass fiber (U)/random glass fiber (R)/epoxy hybrid and non-hybrid composites have been investigated experimentally and theoretically. The effect of stacking sequence and random fiber relative volume fraction (VfR/VfT) in hybrid composites were reported. Laminates were fabricated by hand lay-up technique with a total of 5 plies, by varying the number and position of random glass layers so as to obtain four different hybrid laminates; i.e. [0.5R/U/U]S, [U/0.5R/U]S, [U/U/0.5R]S, and [U/R/U/R/U]. All unidirectional fiber laminate [U]5 and another of all random fiber laminate [R]5 were also fabricated for comparison purpose. The average thickness of the manufactured laminates is 5.5 ± 0.2 mm and the total fiber volume fraction (VfT) is 37%. Failure modes of all specimens were investigated. Results indicated that the in-plane shear properties (shear strength τxy and shear modulus Gxy) of unidirectional fiber composite can be considerably improved by incorporation of random glass fiber and forming hybrid composites.