Abstract
Impact damage is a major concern for the new generation of aircraft composites structures due to the low impact resistance of these materials. Development of an impact force location and force identification system would make maintenance procedures more efficient by allowing inspections to be scheduled only when necessary, and knowing the impact location would allow for a localized search, saving time and cost. Moreover, measuring the impact force would allow to predict damage initiation since delamination area is a function of the impact force and energy. State-of-the-art impact force reconstruction algorithms use reference data from numerical simulations and require a detailed knowledge of mechanical properties, which are difficult to obtain under real operational conditions.
This paper presents an impact force reconstruction algorithm that relies on experimental structural responses measured by a sparse array of surface bonded receiving ultrasonic transducers. This algorithm uses time reversal method to retrieve the location of impact source and interpolation techniques based on hierarchical radial basis functions to calculate the transfer function at the impact point and reconstruct the impact force history. A number of impact testing were performed on a composite plate-like structure and a wing stringer-skin panel, and compared with impact force algorithms available in literature. Experimental results revealed that the proposed hierarchical impact force reconstruction method was able to extrapolate the information associated with points far from the impact location and determine the impact force history with high level of accuracy in a real aircraft structure. Since the proposed algorithm requires the calibration of transfer functions from a very sparse training set of data and it does not need numerical models of the component under investigation, it demonstrates its potential as a useful monitoring tool for impact force reconstruction in composite components for full-scale aircraft structural applications leading to timely and cost-efficient inspections.