Ultrasonic pulse-echo reflection and through-transmission methods for porosity measurement in carbon fiber-reinforced polymer composites

Abstract

To detect void defects and determine porosity levels, carbon fiber-reinforced polymer composites were characterized through two kinds of ultrasonic methods, namely pulse-echo reflection and through-transmission. In order to evaluate the ability and the advantages of these two series of experiments, the tests were carried out on a set of specimens, which were manufactured to vary the porosity by altering the pressures used during the cure cycle in an autoclave. The ultrasonic experimental measurements were shown to be in good agreement with metallographic tests in the porosity range of 0.0% to 3.0%. Despite the consistency of both techniques, ultrasonic pulse-echo reflection method has shown itself to be more sensitive to sub-millimeter voids and more capable of evaluating porosity of lower levels, whereas ultrasonic through-transmission method provides better penetration with regard to higher levels of porosity or thicker plates.

Keywords

• carbon fiber-reinforced polymer composites (cfrp)
• porosity
• pulse-echo reflection
• trough-transmission
• non-destructive testing
• statistical properties