In-situ Tensile and Fatigue Testing for Detection of Interfacial Debonding between Carbon Fibers and Epoxy Matrix by Synchrotron Radiation X-ray Nano-CT

The direct observation of the interfacial debonding between carbon fibers and an epoxy matrix was achieved through in-situ tensile fatigue testing on beamline a synchrotron radiation facility, SPring-8. Preliminary tests were conducted using miniature specimens with multiple embedded under high magnification digital microscope. static loading-unloading revealed clear nominal stress 50 MPa indicated initiation at 30 MPa. Synchrotron X-ray computed tomography (CT) employed to observe internal shape debonded interface. Although it hardly visible conventional absorption contrast CT (micro-CT), 3-dimensional interface clearly observable high-resolution phase-contrast (nano-CT), even initiated where neighboring closely spaced loading. Debonding did not propagate cyclic loading; however, further propagation confirmed along exterior fiber bundles.