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Fracture behavior of unidirectional graphite/epoxy composite materials is
investigated. Single-edge notched coupons are studied under geometrically
symmetric impact loading. The notch orientation parallel to or at an angle relative
to the fiber orientation is considered to produce mode-I as well as mixed-mode
fracture. Stress-wave induced crack initiation and rapid crack growth events are
studied using the digital correlation technique and high-speed photography.
Surface deformations histories in the crack-tip vicinity are obtained by analyzing
speckle image recordings. Measured deformation fields are used to extract mixedmode
fracture parameters and examine the effect of fiber orientation on crack
initiation and growth behaviors. The maximum crack speed observed is the
highest for mode-I dominant conditions and decreases with increasing fiber
orientation angle. With increasing fiber orientation angle, crack takes longer to
attain the maximum speed upon initiation. The crack initiation toughness values
decrease with increasing degree-of-anisotropy.