[1C5] Guided wave transmission around a CFRP L-stiffener
F Hervin¹,², V Maes², P Fromme³, R Hughes² and P Wilcox²
¹GKN Aerospace Services Ltd, UK
²University of Bristol, UK
³University College London, UK
Carbon fibre-reinforced polymer (CFRP) composites are increasingly used to manufacture aircraft components such as fuselage, stiffeners and wing spars, enabling the design of lightweight structures with complex geometries whilst maintaining strength. However, CFRP is prone to subsurface damage (for example delamination) due to low-velocity impacts. Ultrasonic guided waves are elastic waves that propagate along structures, enabling rapid interrogation of large areas and inspection of hard-to-reach regions, and are a potential candidate for in-situ structural health monitoring (SHM). The majority of studies on guided wave propagation in composites are restricted to flat plates, with limited work on wave propagation in more complex components such as C-, T- and L-stiffeners. The sharp bends in the laminates are particularly prone to damage, resulting in significant strength reduction in these regions. Reliable non-destructive evaluation (NDE) and SHM techniques are therefore required to inspect composite components with complex geometries.
A quasi-isotropic CFRP corner section was manufactured with film insert delaminations in the flange and in the corner of the part, respectively. The position and shape of the delamination were validated through ultrasonic phased array scans in immersion. Guided wave propagation and scattering was investigated experimentally using bonded piezoelectric discs to generate the fundamental antisymmetric (A0) Lamb wave mode and a laser Doppler vibrometer was used to capture wavefield measurements. Wave propagation around the bend in a pristine region of the sample is studied to determine the degree of mode conversion and reflection due to the corner itself, before considering the effect of delamination on wave scattering. Good wave transmission is achieved through the corner section of the specimen.
A quasi-isotropic CFRP corner section was manufactured with film insert delaminations in the flange and in the corner of the part, respectively. The position and shape of the delamination were validated through ultrasonic phased array scans in immersion. Guided wave propagation and scattering was investigated experimentally using bonded piezoelectric discs to generate the fundamental antisymmetric (A0) Lamb wave mode and a laser Doppler vibrometer was used to capture wavefield measurements. Wave propagation around the bend in a pristine region of the sample is studied to determine the degree of mode conversion and reflection due to the corner itself, before considering the effect of delamination on wave scattering. Good wave transmission is achieved through the corner section of the specimen.
