Thermo-Mechanical Identification of Orthotropic Engineering Constants of Composites Using an Extended Non-Destructive Impulse Excitation Technique

Composite materials are increasingly used in various vehicles and construction parts, necessitating a comprehensive understanding of their behavior under varying thermal conditions. Measuring the thermo-mechanical properties with traditional methods such as tensile testing or dynamical mechanical analysis is often time-consuming and requires costly apparatus. This paper introduces an innovative non-destructive method for identifying the orthotropic engineering constants of composite test sheets as a function of temperature. The proposed technique represents an advancement of the conventional impulse excitation technique, incorporating an automated pendulum exciting mechanism and creating digital twins of the test sheets. The automated measurement of the impulse response function yields resonance frequencies and damping ratios at specified temperatures. These values are subsequently utilized in digital twins for identification of the engineering constants. The method is fully automated across predefined temperature intervals and can be seamlessly integrated into existing climate chambers equipped with remote control facilities. The results obtained from the described measurement technique were applied to a bi-directionally glass-reinforced thermoplastic PA6 matrix in a tested temperature range of −20 °C to 60 °C, revealing that the complex engineering constants are significantly affected by temperature.