Characterizing fracture behavior of CFRP materials using PWAS-enhanced inspection

Javier Hernández Oliván (ΙΤΑ) presented the study on the delamination in a Carbon Fiber Reinforced Polymer (CFRP) substrate by monitoring a standard static test using Ultrasonic Guided Waves (UGW) with Piezoceramic (PZT) and Macro Fiber Composite (MFC) sensors at the 11th EWSHM 2024 conference.

Abstract

Fracture parameters play a crucial role in characterizing the behaviour of fibre-reinforced polymer materials under various loading and crack propagation conditions. These parameters are typically extracted from mechanical tests, with the Double Cantilever Beam test and flexural experiments involving both three-point and four-point bending being the most common methodologies.
In the context of Structural Health Monitoring (SHM) systems, a reliable feature extraction and selection methodology is essential to assess the mode of material failure. Even in controlled laboratory conditions, such as crack opening tests (Mode I or II), the presence of simultaneous phenomena like fibre fracture and matrix cracking complicates the process of feature extraction and selection, particularly in identifying fracture characteristics.
This study presents the results of standard fracture tests conducted on CFRP (Carbon Fiber Reinforced Polymer) test specimens. These specimens were instrumented with piezoelectric wafer active sensors (PWAS) to perform both, active and passive non-destructive inspections during static and fatigue testing. Ultrasonic guided wave (UGW) inspections, performed on demand, takes advantage of actively exploring large areas with relatively low attenuation. Conversely, acoustic emission (AE) allows for continuous monitoring to detect the initiation, progression, and extent of damage.
The combination of continuous and on-demand techniques provides a comprehensive view and valuable insights into the mechanisms driving fracture modes. When compared to fracture parameters obtained through conventional methods, our findings reveal a strong correlation in terms of damage type and extent for both inspection approaches. This establishes a solid foundation for the development of a future damage classification system based on AE and UGW measurements.