ABSTRACT: In this work an evaluation of the fracture mode of fiber reinforced resin matrix composites submitted to three point bending dynamic impact testing was undertaken. The unidirectional glass, carbon and aramid fiber-epoxy matrix composites used were fabricated by vacuum bagging prepreg laminas. The energy absorbed to fracture the composites had an inverse correlation to the fibres' elastic modulus. The carbon fiber composites failed in a brittle mode. The analysis of the fracture surfaces showed that for the glass fiber composites, the failure is controlled by a coupled mechanism of shear along the fiber-matrix interface and tension transverse to the fibers. The delamination failure observed for the aramid composites was mainly due to the tensile component of stress acting perpendicular to the fibers. In these composites an extensive peeling at the fibers surface was also observed. The impact behavior of the carbon fiber composites could be modelled by a purely elastic analysis. The elastic model underestimates the energy absorbed by the glass fiber composites, but the difference between the experimental and calculated values is not high. The aramid composites could not be modelled by the elastic analysis performed.
Composites; dynamic loading; fractography
