Linear phased array of piezoelectric transducers for delamination monitoring in a composite laminate using Lamb waves

摘要

Applications of Linear Phased array concept have been extended from electromagnetic antennae to many other areas due to their capability to direct, magnify and pick up energy in and from desired directions. Apart from radar, optics and medical imaging, one such growing area is in the non-destructive testing of structures. The extensive use of linear array can be attributed to the attenuation of the waves generated in the structure due to inherent damping and loss in the materials and discontinuities. Linear phased arrays are used as actuator in ultrasonic imaging and diagnostics to magnify the energy at a given direction or point in the structure. In the present work the property of amplifying the wave generated in a particular direction is exploited and is studied on a carbon composite structure. Almost all of the existing imaging methods in context of phased array are based on through thickness and bulk wave modes. In the present research we employ Lamb wave which propagates in a doubly bounded media like structural panels. The spreading of energy in a composite laminate is studied in the form of lobe patterns obtained using amplitude of symmetric Lamb wave mode (SO) with a particular orientation of the linear array with fiber direction. The effect of damage in the form of a delamination in a CFRP composite plate on the lobe pattern is analyzed.