Ultrasonic Porosity Measurement in Carbon Fiber Epoxy Laminates

In this research, through-transmission ultrasonic (TTU) Acoustography was applied to measure and quantify porosity levels in carbon fiber reinforced plastic (CFRP) composite laminates. This study employed several CFRP specimens with wide ranges of porosity prepared by altering the curing pressure during the processing stage. The Acoustography method, operating at 5 MHz and 3.8 MHz, was able to show contrast in ultrasonic images obtained for composite laminates with varied porosity levels. Porosity levels in composite laminates were quantified using acid digestion technique. Also, 3-point bending tests were conducted to investigate the effect of porosity in composite laminates. From the results obtained, it was demonstrated that the mechanical property, inter-laminar shear strength (ILSS), of CFRP decreased with the increasing void content. In addition, ultrasonic attenuation in CFRP laminates were related to varied porosity levels. These findings are significant because Acoustography is being developed as a faster alternative to traditional ultrasonic inspection of composites and porosity is an important anomaly to quantify utilizing NDE methods.

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