Measurement of Elastic Constant Matrix of Carbon Fiber Composites with an Ultrasonic 2D-Array Transducer

The use of carbon fiber reinforced polymer (CFRP) composites is gaining popularity in various industries. Due to its anisotropic nature, the characterization of the mechanical properties of CFRP is challenging. The current practices for determination of the elastic properties of CFRP materials are through destructive testing methods, which is not feasible in many in-situ scenarios. This paper presents an in-situ and non-destructive method to characterize elastic properties of CFRP plates by using an ultrasonic 2D-array transducer. The ultrasonic 2D-array transducer was made of 64 piezoelectric elements and the measurement is automated by an advanced ultrasonic system. An automated time-of-flight extraction algorithm was used based on peak detection of ultrasonic signals. The elastic constants of the CFRP plates were calculated based on the Christoffel equation. This method was validated by ultrasonic through-transmission method by using two discrete ultrasonic transducers. Complete elastic constant matrix measurements for unidirectional and quasi-isotropic CFRP plates were demonstrated using the proposed method. This method has higher positional accuracy, faster testing speed, and better consistency compared to through-transmission method. This work can also be applied for in-situ structural health monitoring of elastic properties changes of materials and structures.