Free-Vibration Analysis and Material Constants Identification of Laminated Composite Sandwich Plates

Identification of material properties of composite materials using nondestructive vibrational evaluation approaches: A review

“…In practice, the Rayleigh-Ritz method is said to be applicable to all plate problems, linear or nonlinear, since the principle of virtual displacements applies to all plate problems [100]. The application of Rayleigh-Ritz technique for forward computation of natural frequencies in the study of elastic properties determination can be seen in [57,63,65,67,68,[101][102][103][104][105]. Most of the investigations are done on thin rectangular orthotropic plates [57, 63, 101-103, 105, 106], followed by thin rectangular laminated plates [65,67] and thick rectangular Sandwich plates [68,104] with combinations of free-clamped edges [57,63], free edges [101][102][103][104][105][106], and elastically-restrained edges [65,67,68].…”

“…For problems with boundary conditions other than simple support or for problems involving generally orthotropic laminates, the application of trigonometric series is complicated. Thus, polynomial series came into existence and have been extensively used in computing the natural frequencies of plates due to its straightforward algebraic manipulation [65,67,68,104,107]. The use of this series is limited in the mid-1980s due to complication in setting up series compromising the geometric boundary conditions.…”

“…The outcomes showed that the orthogonal polynomials led to better convergence. Lee and Kam adopted a set of Legendre's orthogonal polynomials to predict the natural frequencies of partially restrained thin laminated plates [65], elastically restrained thin laminated plates [67], and free-edged thick laminated Sandwich plates [68]. The difference between partially and elastically restrained was the inclusion of additional strain energy stored in the center spring in elastically restrained laminated plates.…”

“…The selection of different types of vibrational experimental methods as well as forward methods and inverse methods in the numerical evaluation section would incur significant In accordance to the development of Fast Fourier Transform (FFT) analysers and virtual instruments, impulse excitation technique has been widely used since in late 1970's. Impulse technique is often the primary choice in the study of material elastic properties identification due to its simplicity and inexpensive procedures, as shown in [56][57][58][59][60][61][62][63][64][65][66][67][68][69][70]. Till today, there is only ASTM standard procedure provided for testing isotropic materials but none for anisotropic materials.…”

“…The more the types of materials used in a multi-layered plate, the higher the number of vibration tests are required. Vibrational experiment that involves impulse technique is commonly regarded as impact testing as depicted in Figure 4 [69], in which an impact hammer is usually used as the exciter and contactless eddy current proximity transducers (displacement) [57], accelerometers [56,58,59,62,65,[67][68][69][70], microphones [60,61], or Laser Doppler Vibrometer (LDV) [63,64,66] are used as the response detectors. However, the drawbacks of this technique are its low reproducibility of input characteristics (manual excitation) and non-applicability to light and brittle objects.…”