The scope of the paper includes non–destructive assessment of the structure's material condition, for the aerospace
structures during its useful lifetime. The paper presents multidisciplinary technologies devoted to development and
implementation of methods and systems that realize inspection and damage detection by non–destructive methods.
The paper covers several disciplines which are based on topics such as piezoelectric transducers, elastic waves
propagation phenomenon, structural vibrations analysis, electro–mechanical impedance method, terahertz technique,
laser induced fluorescence and 3D laser vibrometry applications.
Among various techniques available the paper presents selected numerical simulations and experimental validations of
considered structures. Authors address also the problem of adhesive bonding in the case of carbon fiber reinforced
polymers (CFRP). Techniques for detection of weak bonds are presented together with signal processing approaches.
The reported investigations concern weak adhesive bonds caused by both manufacturing (e.g. release agent, poor curing)
and in–service contaminations (e.g. moisture). Also the paper provides helpful information about dispersion, mode
conversion and wave scattering from stiffeners and boundaries. It addresses the problem of optimisation of excitation
signal parameters and sensor placement, as well as analysis of signals reflected from damage. It also includes a variety of
techniques being related to diagnostics (damage size estimation and damage type recognition) and prognostics.