Mechanical and failure behavior of composite materials under static and dynamic loading

Composite materials were characterized under quasi-static and dynamic loading and failure theories were developed/expanded to describe static and dynamic failure under multi-axial states of stress. The materials investigated were unidirectional glass fiber/vinylester, and carbon fiber/epoxy composites. Multi-axial static and dynamic experiments were conducted using off-axis specimens to produce stress states combining transverse normal and in-plane shear stresses. A Hopkinson bar apparatus was used for multi-axial characterization of the above materials at high strain rates. Quasi-static and dynamic failure envelopes were obtained by the various available failure theories including the recently introduced Northwestern (NU) theory and compared with experimental results. The NU theory was extended to the dynamic loading regime and was shown to be in excellent agreement with experimental results.