Paper number 1317


Demirkan Coker1, Ares J. Rosakis1 and Yonggang Y. Huang2

1Graduate Aeronautical Laboratories, California Institute of Technology
Pasadena, CA, USA 91125
2Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign, Urbana, IL, USA 61801

Summary Some recent experimental observations of highly dynamic crack growth events in thick unidirectional graphite fiber-reinforced epoxy matrix composite plates are presented. The composite plates were symmetrically (mode-I) and asymmetrically (mode-II) loaded in a one-point bend configuration with an edge pre-notch machined in the fiber direction. The lateral shearing interferometric technique of coherent gradient sensing (CGS) was used in conjunction with high-speed photography. Symmetric, mode-I cracks initiated at 1300 m/s and subsequently accelerated up to the Rayleigh wave speed but never exceeded it. For asymmetric, Mode-II types of loading, the results reveal highly unstable and intersonic, shear-dominated crack growth along the fibers. The intersonic cracks propagated with unprecedented speeds reaching 7400 m/s, more than three times the shear wave speed of the composite, and featured a shock wave structure typical of disturbances travelling with speeds higher than one of the characteristic wave speeds in the solid.
Keywords dynamic fracture, crack propagation, intersonic, unidirectional composite, shear crack growth, mode-II crack growth.

Theme : Industrial Applications ; Marine Applications

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