Abstract
Aerospace vehicles are demanded to withstand harsh conditions with a low weight impact. Composites have been increasingly adopted to meet such performances but they are affected by sudden and barely visible failures when subjected to low velocity impacts. The design criteria and the maintenance tasks in a damage tolerant approach are unavoidably compromised. Structural Health Monitoring is expected to avoid typical accommodations employed during design and lifetime management by achieving a cost-effective and on condition maintenance. This paper describes the use of guided ultrasonic waves excited and sensed by permanently attached piezoelectric transducers for detection and localization of unforeseen and hidden flaws in composite structures. A composite stiffened structures designed for real scale components is investigated to test a multi-parameter detection technique capable of predicting different wave features affected by hidden failures to detect any possible change in the structure. Usually, propagation behavior is exploited to detect changes in the waveguide focusing on the analysis of an intrinsic feature of the propagating wave. Numerical simulations and measurements carried out on a real-scale aircraft structure demonstrate that increasing the observed characteristics improves the result making efficient the diagnosis. Furthermore, it is shown that accounting a multi-parameter analysis of ultrasonic data enhances the localization reliability making use of the same reconstruction algorithm with data fusion approach while facing with different kind of damages.
Highlights
Performances are key concerns in the field of transportation engineering where aerospace vehicles require safer structures with as little consumption as possible
Data acquisition, where the guided waves are recorded during aircraft parking according to the interrogation mode and stored for analysis; data processing, which deals with the analysis of stored data to extract features possibly affected by the damage; decision-making process, where the minimum metric associated to a damage with a reasonable confidence is established; and damage reconstruction, which deals with all algorithms aimed at a certain diagnosis, no matter what is the level of the estimation
The structural health monitoring based on guided wave propagation is here operated through several steps, which are the same whether simulations or experiments are considered
Summary
Performances are key concerns in the field of transportation engineering where aerospace vehicles require safer structures with as little consumption as possible. To achieve higher performances with lighter components, composite materials replaced classic aluminum alloys even in primary structures. An important aspect consists of the flexible design of the structure according to tailorable properties of composite materials [1], making them even more efficient for load cases and conditions typically withstood by aerostructures [2]. Aircrafts made of composites require far fewer parts, so there is less to bolt together and the possibility to create structural components with fewer connections possible. Looking for operational efficient aircrafts, the use of composites improves passenger comfort. Composites are even tougher than aluminum alloys and the higher durability should allow maintenance costs to be much lower than for aluminum planes
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