Lamb Wave Reflection And Transmission In Composite Beams Structures With Damage

Since structural health monitoring using Lamb wave has been widely employed in aerospace and large civil structures, it is significantly important to develop a theory to mode the Lamb wave propagation behaviour in damaged structures.In this study, Lamb wave propagating in composite beams are first modelled analytically using both higher-order beam theory and elasticity beam theory, and the dispersion relations of the waves are established. Comparing the results of the two analytical theories finds out that the lower modes such as A0, and S0 are matched well in the whole frequency domain, and the higher modes such as A1 and S1 are approximately closed in the lower frequency domain.Base on these, wave propagation in beams containing damage such as inhomogeneity or delamination is studied. When the propagating Lamb wave reach the damage position, it will partially reflects back into the un-damaged region and partially transmits into the damaged region of the beam, and also there is a mode conversion between each Lamb mode. For the inhomogeneity, the different damage degree is researched to find out the different wave reflection and transmission coefficients. For the delamination, two extreme cases: non-contact (open) and fully contact (closed) delamination are considered to examine the wave reflection and transmission.In addition, power flow, a scalar description of energy reflection and transmission together with mode conversion of energy, is varied with different damage degree and damage position. Meanwhile a finite element method is employed to simulate the wave propagation in the damaged beam, and results show that it is coincided with the analytical method, which verifies the validity of the analytical method. And this provides an efficient theory for initiative monitor technology.