Detection of Hidden Defects in Composite Material Using the Standing Waves Method

As a result of measurements carried out using the standing waves method, hidden defects were detected inside the prosthetic feet details made of composite material. When comparing the obtained amplitude-frequency spectra of intact samples and samples with defects based on the first peaks corresponding to the first bending wave modes, it was revealed that the values of the resonant frequencies of defective samples were lower relative to the frequency values of the spectra of the intact ones. That observation indicated that the material of defective products might have reduced strength characteristics. Also, when studying some samples, the presence of additional peaks was noted, which indicated the appearance of new reflection boundaries corresponding to the appearance of defects in the test samples. The maps of amplitude distributions in the studied samples were obtained. A preliminary comparison was made with the results of examining samples using the OmniScan X3 device manufactured by OLYMPUS company. The results obtained indicated the presence of an increased number of reflection boundaries, as well as an increased bulges content, which probably arise during the process of products gluing. The analysis confirms the possibility of successfully using the standing waves method as a method for detecting hidden defects in composite material.