Characterization of in-plane shear properties of laminated composites at high strain rates

The in-plane shear responses of continuous fiber reinforced composite materials under high strain rates were characterized experimentally. The V-notch rail shear configuration was used for characterizing the in-plane shear behavior of Newport NB321/3k70 plain weave carbon fabric/epoxy, NCT/321/G150 Carbon Fiber Unitape/epoxy, NB321/7781 fiberglass/epoxy, Cytec PWC/T300/3KNT plain weave carbon fabric/epoxy and Fibercote 3KPW/E365 plain weave carbon fabric/epoxy systems. The testing was conducted using a servo hydraulic testing machine at nominal stroke rates ranging between 0.00083in/sec to 500in/sec. A maximum average shear strain rate of 654rad/sec was achieved up to shear strain levels of 0.08 radians, during the tests. The stress-strain behavior of all material systems exhibited contrasting behavior with increasing stroke rates. The stress-strain curves for all materials exhibited an asymptotic behavior for stroke rates approaching 10in/sec and were material dependent for stroke rates exceeding 250in/sec. For Newport NB321/3k70 and NB321/7781 systems at the highest test rate, the shear strengths increased by a factor of three relative to that of the quasi-static rate, and were independent of the reinforcement type. The shear strength for Cytec PWC/T300/3KNT, Fibercote 3KPW/E365 and Newport NCT/321/G150 increased until a stroke rate of 100in/sec and later decreased with increasing stroke rate. The failure modes for Cytec PWC/T300/3KNT, Fibercote 3KPW/E365 and Newport NCT/321/G150 were at the minimum section of the shear coupons, while for Newport NB321/3k70 and NB321/7781, failure was observed to change from a shear mode across the minimum section to a complex failure mode away from the minimum section.