Active Infrared Testing of Composites using 3D Computer Simulation
Published at : 29 Apr 2018
Volume : IJtech
Vol 9, No 3 (2018)
DOI : https://doi.org/10.14716/ijtech.v9i3.218
Protasov, A., 2018. Active Infrared Testing of Composites using 3D Computer Simulation. International Journal of Technology. Volume 9(3), pp.631-640
| Anatoliy Protasov | - Department of Non-Destructive Testing Devices and Systems,
National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute", Kyiv, Ukraine
- |
Composite sandwich constructions are very widely employed in the modern aircraft industry, honeycomb panels among them. The principal defects of honeycomb sandwiches are cover detachment because of cell collapse or poor adhesive, which can lead to water penetration in cells. Recently, the thermal method of non-destructive testing (infrared thermography) has begun to be applied to the diagnostics of honeycomb constructions, and has some advantages over traditional methods. However, thermal processes are transient, and this complicates the selection of optimal parameters for monitoring. The purpose of this work is to investigate the possibilities of the thermal method for honeycomb panel inspection using computer simulation. The COMSOL Multiphysics package was used for the simulations. A 3D model of the honeycomb panel was proposed, and two possible defects considered: the detachment of the panel cover from the filler and the presence of water in the defective cell. The implementation of the proposed 3D model made it possible to investigate the effect of a defect on the thermal field of the panel surface. The simulation results showed that optimal testing time is significantly different for various types of panels. The correct selection of testing parameters increases the accuracy of the testing procedure. The results of experimental investigation confirmed the adequacy of the proposed model for thermal testing.
Composite materials; Computer simulation; Infrared testing; Three-dimensional model
Multi-layer composite materials are widely used in modern aircraft construction. They are characterized by high strength and low specific gravity (Ibarra-Castanedo et al., 2007). In aircrafts of the latest generation, more than 30% of the fuselage, wing, keel and other parts of the aircraft are made of honeycomb panels (Vavilov & Nesteruk, 2005).
The principal defects of honeycomb sandwiches are the detachment of the cover from the filler due to the non-gluing or crushing of the cells. These defects can arise both during the operation of the aircraft and during the manufacture of honeycomb sandwiches, because of process violation. The most dangerous defect is the ingress of water into the cellular structures of the airplane elements (Meng, 2008; Oliveira et al., 2011). At low temperatures, water freezes and increases its volume, which leads to the destruction of honeycomb cells and significantly reduces the strength of the entire panel design. The traditional methods of defect detection in
Recently, the active thermal method of testing (active
thermography) has begun to be applied to the diagnostics
of composite materials, as it allows users to identify any defect in the material structure (Galietti & Palumbo, 2016) and has certain advantages over traditional methods.
It is non-contact, allows the exploration of large areas in a relatively short
time, and poses no risk to the safety of personnel (Sánchez-Carballido
et al., 2014; Yu et al.,
2014). Thermographic
techniques use an external heat source to excite thermal waves in the material.
The presence of a defect causes various thermophysical local properties of the
material, which leads to abnormal temperatures on the material surface. The
ability of thermography to detect defects in honeycomb panels has been
demonstrated in various works. The use of pulse thermography to detect the
penetration of water into composite honeycomb panels was investigated by Meng
(2008), Oliveira et al. (2011), and Xingwang and Feifei
(2012). Zhao et al. (2011) researched pulse
thermography to detect not only water but also hydraulic oil in sandwich
panels. The quantitative estimation of water content in aircraft honeycomb
panels using transient infrared thermography was carried out by Vavilov and
Nesteruk (2005).
The active
infrared testing method is successfully applied to the inspection of the condition of aircraft structural
elements in companies such as Airbus Industry, Inc. and Boeing.
Although this
method of testing has begun to be applied in industry, the received results of
the research are insufficient for its full and wide application. The influence
of material structure parameters and heating parameters on the detection effect has not been studied completely. In addition, there are some problems connected to flaw detection in honeycomb structures
made of aluminum alloys and composites. Aluminum constructions have high
thermal conductivity, which provides transience of all heat processes; this
impedes the testing procedure. Composite structures retain high
temperatures for a long time. This enables the
tester to obtain a more
precise
result. Thus, different honeycomb structures need to be inspected using different modes of
testing.
The
obtained results confirm the possible applicability of the COMSOL Multiphysics
package to study the processes that occur under active thermal testing of
honeycomb panels. Honeycomb panels are of a complex composite material, the
constituent parts of which have different thermophysical properties, which significantly
affects the parameters of thermal testing. The implementation of the proposed
3D model for computer simulation makes it possible to investigate the thermal
processes that occur inside the object during testing, which cannot be
determined experimentally. This makes it possible to preliminarily determine
the necessary testing parameters, namely, the optimum monitoring time and the
heating temperature for each specific case. This improves the accuracy of
monitoring the honeycomb panels. The results of experimental studies confirm
the adequacy of the proposed model of thermal testing.
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