Skip to main content

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

Periodic Reporting for period 2 - CompInnova (An Advanced Methodology for the Inspection and Quantification of Damage on Aerospace Composites and Metals using an Innovative Approach)

Reporting period: 2016-09-01 to 2018-10-31

Aerospace industries are obliged by Aviation Authorities to inspect all aircraft components for defects/flaws, before and during their service life. In most of the cases a reliable and efficient Non Destructive Testing (NDT) techniques are applied. Aircraft maintenance costs could be up to 20% of the overall operating costs, but inefficient and ineffective inspection could increase it by 50% or more, leading to catastrophic failures and eventually result in aircraft and life loss. Thus, there is a huge industrial and scientific interest in highly efficient and reliable damage inspection and proper repair of composite aero-structures.
Therefore, the main motivation of the CompInnova project is to develop an innovative automated multifunctional Vortex robotic system for aircraft inspection and repair. The system will incorporate a ultrasonic Phased Array (PA), Infrared Thermography (IRT) equipment for inspecting composite aircraft structures and a novel laser material removal and repair system. This solution will improve maintenance quality and productivity while reducing time and cost.
The ultimate objective of the CompInnova project is to deliver innovative automated maintenance and repair solution capable to detect, evaluate and repair damages in composite aircraft components. The project will develop a novel and adequate PA technique for inspection of complex surfaces (e.g. fuselage), develop novel fusion approach for PA and IRT techniques for reliable automatic detection and depth assessment of various defects in composites; provide 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 inspection.
During the first period, the consortium has established the requirements and specifications of the project and performed a detailed literature reviews on the mechanical behaviour of metallic and composite materials for aircraft structural parts, review of typical defects in aircraft structures and NDT approaches for their detection, review on applications and automation challenges in using PA and IRT for aircraft maintenance, review on lasers and their use for repair purposes and review of the 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 novel combination of different actuation methods while carrying the NDT and repair equipment.
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 has been employed in testing . 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 for the repair module(s) was developed with the view to be incorporated in the Vortex Robot. A prototype of the system for composite material removal based on lightweight green laser was built at the premises of UoP and successfully evaluated.
Development of defect characterisation software and an online MySQL storage database able to collect and store a vast amount of PA and IRT data in real time has been initiated. Successful experiments with defect detection and characterization algorithms have been completed.
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. Two concepts of a Vortex Robot (VR) incorporating modules for inspection and repair are presented: a single automated VAS-based setup and a multiple robots concept, increasing the inspection and repair efficiency.
- Completed the development and evaluation of functionality of the Near Infrared thermographic technique and hardware for assessing damages in transparent and semi-transparent aircraft parts, such as delaminations from impacts on composite fuselage. Fine-tuning the thermographic method was performed in order to assess the detectability of delaminations, accounting for their size, depth, and the thermal properties of the surrounding composite material.
- Developed a PA imaging technology for in-service inspection of composite material going beyond the current state-of-the-art: it is composed of a custom rubber wedge for 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. A mixed approach resorting to hardware and software solutions has been used in order to enhance the resolution of defects localisation 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 validated FE models. A successful 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.
CompInnova, is at this stage progressing beyond the state of the art presented by novel concept for automated maintenance and repair of composite aircraft structures supported by prototypes of SSVR based on innovative VAS, novel PA and IRT modules ready for integration with SSVR and innovative laser system for material removal and repair, with corresponding software components for each part. Consortium aims to demonstrate at the end of the project a fully functional prototype of robotic maintenance 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. It is expected that this solution will make an economic impact on businesses involved in manufacturing and maintenance of composite parts for aerospace industry and enhance competitiveness of European aircrafts, higher safety standards and lower through-life cost by enabling lighter and more reliable composite airframes.