Quantitative Evaluation of Interlaminar-Toughened CFRP Composite by Ultrasonic Wave Propagation Characteristics

The interlaminar-toughened CFRP composite, T800H/3900-2, has interlaminar resin layers, whose thickness is about 20 mm. The interlaminar layer was evaluated quantitatively using an ultrasonic micro-spectrometer (UMSM) for the determination of the elastic constants, which is quite difficult by other techniques. At first, the composite was ground to remove the outermost CFRP layer, and the interlaminar layer was exposed. Then the acoustic reflection coefficients at a small spot on the surface of the interlaminar layer were measured using the UMSM. The magnitude of the reflection coefficients is related to the properties of the layer. Hence, the elastic constants of the interlaminar layer were obtained appropriately through the fitness of theory to the magnitude of the reflection coefficients. Moreover, the obtained Young’s modulus was compared with that measured by tensile tests.