Fabrizio Ricci

This paper deals with guided wave-based structural health monitoring of composite overwrapped pressure vessels adopted for space application. Indeed, they are well suited for this scope thanks to their improved performance compared with metallic tanks. However, they are characterized by a complex damage mechanics and suffer from impact induced damage, e.g., due to space debris. After reviewing the limited progress in this specific application, the paper thoroughly covers all the steps needed to design and verify guided wave structural health monitoring system, including methodology, digital modelling, reliability, and noise estimation for a correct decision-making process in a virtual environment. In particular, propagation characteristics of the fundamental anti-symmetric mode are derived experimentally on a real specimen to validate a variety of finite element models useful to investigate wave interaction with damage. Different signal processing techniques are demonstrated sensitive to defect and linearly dependent upon damage severity, showing promising reliability. Those features can be implemented in a probability-based diagnostic imaging in order to detect and localized impact induce damage. A multi-parameter approach is achieved by metrics fusion demonstrating increased capability in damage detection with promising implication in enhancing probability of detection.

Electrical actuation concept fits perfectly with the worldwide strategy of more electric aircraft to reduce carbon footprint. However, the integration of linear electro-mechanical actuators is promising yet challenging in safety critical systems due to the jamming of the driven load. That fault is a critical mechanical transmission failure giving rise to concern in many applications such as primary flight controls or landing gears extension and steering. This article critically reviews electric actuation solutions currently available for aerospace application, the limits for their upcoming deployment and the different solutions to achieve an on-condition maintenance to reduce any safety risk during lifetime. A particular attention is given to the jamming and possible strategies to avoid any hazard induced by this failure. The most promising approach relies on the establishment of a predictive maintenance by monitoring continuously the actuator to timely warn any structural alteration, which is prone to induce jamming. Finally, a case study is presented, showing the ability of engine current monitoring to warn any alteration in the load maneuvering. The current spectrum analysis is found to be sensitive to both mechanical fault and control failure or malfunctioning. On top of that, no addition sensors are needed, making this technique affordable and cost-effective.

During recent years, aircraft manufacturers focused their attention on environmentally friendly and aerodynamically efficient aircraft concepts that could allow a radical reduction of emissions. The use of hybrid-electric powertrain is one of the most effective ways to design near-zero emission aircraft. These aircraft are highly performing and sophisticated. Hence, the design process must be extremely accurate and should make use of multidisciplinary design optimization. It is indeed crucial to establish both aerodynamic and structural models to simulate the aircraft performance and design required according to top level aircraft requirements. Despite the largely discussed literature about preliminary design of such an unconventional aircraft, there is still a lack of reliable weight estimation approaches, simulation-based mission analysis and optimization tools. In order to step towards higher technological readiness levels, the purpose of this paper is to describe and apply a design platform for conventional, turboelectric, hybrid-electric and full-electric aircraft, integrating aero-propulsive interactions, accurate power system modelling and medium-fidelity structural weight estimation. In particular, the comprehensive structural analysis of the aircraft wing opportunely designed according to certification specification and equipped with different powertrain architectures shows that it is worth looking into structural dynamics from preliminary design to estimate aircraft weight properly. Meanwhile, the mission analysis reveals performance benefits by implementing distributed engines all over the wingspan.

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.