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Numerical and Experimental Investigation of Multilayer Delamination Detection in Composites



The extensive use of composite materials in aerospace structures has posed new challenges for implementing guided wave based structural health monitoring (SHM) techniques due to the general anisotropic behavior in composites. Delamination is the most common and dangerous failure mode for composites, because it takes place and grows in the absence of any visible surface damage, making it difficult to detect by visual inspection. Due to the general anisotropic behavior of composites, the successful implementation of delamination detection techniques in aerospace composite structures is always challenging. This paper presents a numerical and experimental investigation to detect the multilayer delaminations in carbon fiber reinforced polymer (CFRP) composite plates using piezoelectric wafer active sensors (PWAS). First, ultrasonic Cscan was conducted to detect and visualize the purpose-built delaminations by inserting Teflon films in a 3 mm quasi-isotropic [-45/90/45/0] CFRP composite plate. Then, a multi-physics three-dimensional (3D) finite element (FE) simulation of the composite plate with multiple delaminations was carried out to understand wave interaction with delaminations, especially the trapped waves due to the multilayer delaminations. Finally, scanning laser Doppler vibrometer (SLDV) measurements were conducted on the composite plate. Wavenumber analysis was used to investigate guided wave interaction with delaminates. It can be found that the wavenumber methods can determine the delaminated region and identify the plies between which the delamination occurs. The results demonstrate a good capability for detecting the presence of hidden multilayer delamination in composite structures.


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