PT  - JOURNAL ARTICLE
AU  - Deganová, Lucia
AU  - Dekýš, Vladimír
AU  - Sapieta, Milan
AU  - Sapietová, Alžbeta
TI  - Ultrasonic-Based Active Thermography for Determining Depth Detection Limits in Onyx Composites
DP  - 2026 Mar 21
TA  - Manufacturing Technology Journal
PG  - 14--25
VI  - 26
IP  - 1
AID - 10.21062/mft.2026.003
IS  - 12132489
AB  - This paper examines the detection of internal defects in composite specimens composed of Onyx, a material featuring a nylon matrix reinforced with chopped carbon fibers. Artificial defects, in the form of flat-bottom holes of various geometries, were intentionally introduced during the additive manufac-turing process. The primary objective is to determine the depth detection capabilities of ultrasound by varying the excitation frequency and determining whether these defects remain identifiable at different subsurface levels. Ultrasonic lock-in thermography is utilized to excite specimens. As the frequency is modified, the depth of wave propagation also changes, a phenomenon well established in homogene-ous materials. However, the heterogeneous nature of Onyx introduces complexities into wave propa-gation. The recorded thermographic data are processed in MATLAB to calculate contrast ratio values, enabling a quantitative comparison of defect detectability for different defect geometries.