Citation: Samarathunga, A.I.;
Piyasundara, N.; Wanigasooriya, A.I.;
Kumara, B.S.; Vithanage, V.P.;
Chathuranga, D.S. A Robotic
Platform for Aircraft Composite
Structure Inspection Using
Thermography. Robotics 2022, 11, 62.
https://doi.org/10.3390/
robotics11030062
Academic Editors: Giovanni
Boschetti and Marco Ceccarelli
Received: 1 March 2022
Accepted: 9 May 2022
Published: 15 May 2022
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Article
A Robotic Platform for Aircraft Composite Structure Inspection
Using Thermography
Amalka Indupama Samarathunga
1,2,
* , Neelanjana Piyasundara
1
, Anuka Iroshan Wanigasooriya
1
,
Buddhika Sampath Kumara
1,2
, Vimukkthi Priyadarshana Vithanage
1,2
and Damith Suresh Chathuranga
1
1
Department of Mechanical Engineering, University of Moratuwa, Katubedda, Moratuwa 10400, Sri Lanka;
wlnpiyasundara@gmail.com (N.P.); happyprincejennyraf@gmail.com (A.I.W.);
buddhika@tech.sab.ac.lk (B.S.K.); vimukkthi@tech.sab.ac.lk (V.P.V.); chathurangas@uom.lk (D.S.C.)
2
Department of Engineering Technology, Sabaragamuwa University of Sri Lanka, Belihuloya 70140, Sri Lanka
* Correspondence: amalka@tech.sab.ac.lk
Abstract:
Water ingression is a critical issue in honeycomb composite structures, which could result
in catastrophic structural failure. In the aviation industry, they are widely used to manufacture critical
aircraft structural components including fuselage, wings, and flight control surfaces. Catastrophic
failure of these structures would be disastrous, thus identifying water accumulation in earlier stages
of the defect is necessary. The conventional non-destructive testing method is thermography which
is performed using handheld thermography cameras by manually accessing the specific areas.
This method of inspection has been identified to be a risky, costly, time-consuming, and inspector-
dependent technique. This paper describes using a wall-climbing robotic platform that can be
controlled remotely to access and perform the inspection on a targeted structural area replacing the
manual process. The designed wall-climbing inspection robot onboard a heat pump to stimulate
the composite surface to an adequate temperature and, an infrared sensor to feed the real-time
temperature data via Bluetooth serial communication to a remote computer system to be processed
into a thermal image and evaluated to determine the presence of water. The results obtained from the
thermographic sensor are validated with the comparison of the Fluke thermography camera.
Keywords:
composite structures inspection; thermography; wall-climbing robot; water ingression;
electric ducted fan (EDF)
1. Introduction
To maintain the reputation for being the safest mode of transportation, the aviation
industry indeed needs regulated, reliable, consecutive aircraft maintenance programs.
In such programs, inspections and accurate damage evaluations of aircraft systems and
components are essential. Non-destructive testing (NDT) methods are often used in such
instances. These tests are used to evaluate the airframe and engine components for damages
and damage initiations preserving the original structural properties. Amidst the main
NDT methods, eddy current testing, ultrasonic testing, liquid penetration inspection (LPI),
magnetic particle inspection (MPI), X-ray, and thermography are prominent [1].
Present-day aircraft structures such as fuselage, wings, and flight control surfaces
are made using composite structures, especially honeycomb composite because of their
high strength-to-weight ratio and, corrosion resistivity properties. Common issues of
the composite structures are debonding, delamination, cracks and dents, burns due to
lightning strikes, and water ingressions are common among them [
2
]. Amidst them, water
ingression is the most critical and vulnerable, as it is damage that cannot be easily detected
through visual examination or using quick conventional inspections. Though voids due
to damages or caused during previous repairs, through loosened fasteners, and through
cracks due to material failures, atmospheric water ingresses inside the honeycomb of the
composite structure. This ingressed water, due to altitude changes during flights, thermally
Robotics 2022, 11, 62. https://doi.org/10.3390/robotics11030062 https://www.mdpi.com/journal/robotics
