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An Advanced Methodology for the Inspection and Quantification of Damage on Aerospace Composites and Metals using an Innovative Approach

Periodic Reporting for period 3 - CompInnova (An Advanced Methodology for the Inspection and Quantification of Damage on Aerospace Composites and Metals using an Innovative Approach)

Reporting period: 2018-11-01 to 2020-12-31

Aerospace industries are obliged by Aviation Authorities to inspect all aircraft components for defects/flaws, before and during their service life. In most cases, reliable and efficient Non-Destructive Testing (NDT) of aerospace components are expected. Aircraft maintenance costs might be up to 20% of the overall operating costs, but inefficient and ineffective inspection could increase it by 50% or more, especially if they lead to catastrophic failures resulting in aircraft and human losses. Thus, there is a huge industrial and scientific interest in having highly efficient and reliable damage inspection and repair procedures, especially for composite aero-structures.
CompInnova project’s main motivation is to develop an innovative automated multifunctional robotic system solution for aircraft inspection and repair. A vortex robotic platform accommodates an ultrasonic Phased Array (PA) and an Infrared Thermography (IRT) modules for the inspection of composite aircraft structures, whilst a robotic manipulator is equipped with a novel laser material removal and repair system. This solution is capable of improving the maintenance quality and productivity while reducing time and cost.
The ultimate objective of the CompInnova project is to deliver this innovative automated maintenance and repair solution capable of detecting, evaluating and repairing damages in composite aircraft components. The project developed a novel, high-resolution, PA damage visualisation technique for the inspection of complex surfaces (e.g. fuselage), and a complementarity approach for PA and IRT techniques for reliable automatic detection and depth assessment of various defects and damages in composites; providing an innovative solution for the problem of bonding composite patch repair in composite aero-structures, and develop a high precision spatial positioning system, capable of tracking the position of PA and IRT sensors during the inspection phase.
During the project, the consortium established the requirements and specifications, reviewed the typical defects in aircraft structures and NDT approaches for their detection, the applications and automation challenges in using PA and IRT for aircraft maintenance, the use of lasers for repair, and a state of the art in wall-climbing robotics.
An outline of specifications and conceptual design of the Vortex Robot Platform (VRP) was performed, aiming to enable successful attachment and motion on the target surfaces via the combination of different actuation methods while carrying the required modules.
Novel IR thermography approach was developed based on the combination of pulsed phase (PPT) and lock-in (LT) IR thermography techniques, as none of the existing techniques can individually perform online damage assessment on the Vortex robot.
Portable PA hardware suitable for in-service inspection was developed and tested. The PA transducer performance requirements were derived from Finite Element (FE) modelling and following laboratory trials with various calibration samples. Methodology for in-service inspection of aircrafts was proposed with review and performance evaluation of suitable signal processing algorithms.
A prototype for automatic laser-based material cutting/grinding of composites was developed. A prototype of the system for composite material removal based on lightweight green laser was built and successfully evaluated, integrated in a manipulator robot.
In the second period the consortium:
- Designed a Vortex Actuation System (VAS) following extensive experimental study, which led to a novel methodology for achieving the optimal adhesion performance. A Small-Scale Vortex Robot (SSVR) utilising the VAS was designed and manufactured with the following experimental evaluation at surfaces of different inclinations.
- Completed the development and evaluation of functionality of the Near IR thermography for assessing damages in transparent and semi-transparent aircraft parts, such as delamination from impacts on composite fuselage.
- Developed a high-resolution (high-frequency and software enhanced) PA imaging technology for in-service inspection beyond the current state-of-the-art: a custom rubber wedge for a high frequency PA transducer, a mist based couplant sub-system, positioning fixture, an ad hoc subsystem for integration in the VR and of a visualization software allowing for 2D and 3D representation of defects in the material.
- Completed development and validated algorithms for defects detection, characterisation and patch geometry calculation integrated into the Graphical User Interface realising the complete workflow.
- Investigated the effectiveness of stepped repair to damaged fibre reinforced composite materials by using FE models. A parametric study was conducted in order to evaluate the influence of the scarf ratio on the integrity of the repaired laminate and the restoration of stiffness. The modules for automated repair of aircraft structures, including material removal and placement of the relevant patch, were designed according to the requirements of the robotic platform and manufactured.
In the last period the consortium:
- Fully integrated the PA and IRT modules on the Vortex robotic platforms. The performance of the robotic inspectors has been tested on a demonstrator composite panel, representative of an aerospace structure, manufactured with stiffeners, copper mesh and painted.
- The influence of repair patch geometry has been assessed using refined FE models.
- The laser-repair module has been fully integrated on a manipulator robotic platform, with an advanced control software. Evaluation of the performance has been done on the demonstrator panel.
- The patch-placer module has been tested on the demonstrator panel, jointly with a porosity assessment of the cured material based on a specialized ultrasonic inspection module.
- The overall solution has been tested on the demonstrator panel, in an integrated way.
- Exploitation of the Vortex Robotic inspectors is being pursued in a sensor-agnostic way.
- Dissemination activities have been carried out about all modules and subsystem developed, and totally 27 scientific publications have been done.
- Results of the project have been disseminated to the general public and industrial partners in a series of ad-hoc events by Cranfield and all the partners. The total outreach is in order of thousands of people that have heard of the CompInnova project.
CompInnova, has progressed beyond the state of the art having developed a potential solution for automated maintenance and repair of composite aircraft structures supported by prototypes of SSVR based on innovative VAS, PA and IRT modules integrated with SSVR and innovative laser system for material removal and repair, with corresponding software components for each part. Consortium was able to demonstrate at the end of the project an integrated prototype of the solution able to detect and characterize defects in the composite aero-structures, remove affected material and thus prepare the composite part for repair patch application. A first economical assessment was made, addressing the potential impact on businesses involved in manufacturing and maintenance of composite parts for aerospace industry and enhance competitiveness of European standards and lower through-life cost. On a first assessment, it is proven the CompInnova solution has the potential to achieve a positive impact.
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