Lamb wave based structural health monitoring shows a lot of potential for damage detection of composite structures. However, currently there is no agreement upon optimal network arrangement or detection algorithm. The objective of this research is to develop a sparse network that can be expanded to detect damage over a large area. To achieve this, a novel technique based on damage progression history has been developed. This technique gives an amplification factor to data along actuator-sensor paths that show a steady reduction in transmitted power as induced damage progresses and is implemented with the reconstruction algorithm for probabilistic inspection of damage (RAPID) technique. Two damage metrics are used with the algorithm and a comparison is made to the more commonly used signal difference coefficient (SDC) metric. Best case results show that damage is detected within 12？mm. The algorithm is also run on a more sparse network with no damage detection, therefore indicating that the selected arrangement is the most sparse arrangement with this configuration. 1. Introduction To achieve lighter aerospace structures, damage is allowed to exist during operation as long as it is within safe, predetermined specifications; aircraft structures are designed according to a damage tolerant philosophy. In more recent years composite materials are being used to build aerospace structures because they are lightweight and stiff and have excellent fatigue and corrosion resistance. The downside to composites, however, lies in their damage mechanisms. Composites may fail or become damaged in a number of ways that are very different from traditional metallic materials. Defects may arise during manufacture due to voids/porosity, ply misalignment, or inclusion of foreign objects that show no evidence to the naked eye. Composites suffer from low velocity impacts that can damage the internal structure of a laminate while leaving no visible evidence on the surface. Maintenance and inspection of aircraft is of utmost importance for safe and efficient operation. Aircraft structures operate in harsh conditions sustaining high loads, fatigue cycles, and extreme temperature differentials. Failure of these structures is not acceptable due to the possibility of loss of life and assets. To ensure aircraft structures are in safe operational condition, costly inspection involving aircraft downtime and often disassembly of major components is routinely performed. The cost of inspection is about 30% of the total cost of acquiring and operating composite structures [1]. Currently,
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