Different Acoustic Signals in Tensile Testing of Continuous and Short Carbon Fiber Composites

• James Pollock, Mechanical Engineering, University of Delaware

• Amit Chaudhari, Center for Composite Material, University of Delaware

Acoustic Emission (AE) technology is a nondestructive monitoring and analysis tool typically used to assess the health of materials and structures. In tensile testing, carbon fiber composites fail primarily due to fiber breaks, matrix cracking, fiber pullout, and delamination. Continuous and short carbon fibers break differently and have different failure mechanisms. Acoustic emission data collected during the tensile testing of carbon fiber composites can provide information such as the location of the damage and type of failure. In this research, continuous and aligned short-fiber composite specimens were tested in an Instron until failure. The AE data was collected with a single sensor 1-2 inches away from the strain gauge location in the middle of the specimen. Waveforms of each acoustic hit were also generated to study the composite’s damage mechanism. In continuous fiber composite, many hits with waveforms of high amplitudes are generated at load drop, possibly due to fiber breakage. In short fiber composites, acoustic hits start at the initiation of load and continue to increase along the test because failure is governed by matrix cracking. Using the waveforms along with load and strain data generated during testing, the composite failure mechanism is analyzed and reported for continuous and aligned short fiber composites.