The ability of Lamb waves to travel long distances can be harnessed to monitor damage in large structures, such as those used in aerospace applications. This paper reports on studies of the propagation of Lamb waves in composite structures the signal processing techniques used to get information from Lamb wave data. The Short Time Fourier Transform (STFT) is used as a tool for signal processing on Lamb waves. The energy of the Lamb wave signal is employed to reconstruct the image using iterative tomographic algorithms.