Capability of non-destructive techniques in evaluating damage to composite sandwich structures

Abstract

Purpose Defects can be caused by a number of factors, such as maintenance damage, ground handling and foreign objects thrown up from runways during an in-service use of composite aerospace structures. Sandwich structures are capable of absorbing large amounts of energy under impact loads, resulting in high structural crashworthiness. This situation is one of the many reasons why sandwich structures are extensively used in many aerospace applications nowadays. Their non-destructive inspection is often more complex. Hence, the choice of a suitable non-destructive testing (NDT) method can play a key role in successful damage detection. The paper aims to discuss these issues. Design/methodology/approach A comparison of detection capabilities of selected C-scan NDT methods applicable for inspections of sandwich structures was performed using water-squirt, air-coupled and pitch-catch (PC) ultrasonic techniques, supplemented by laser shearography (LS). Findings Test results showed that the water-squirt and PC techniques are the most suitable methods for core damage evaluation. Meanwhile, the air-coupled method showed lower sensitivity for the detection of several artificial defects and impact damage in honeycomb sandwiches when unfocussed transducers were used. LS can detect most of the defects in the panels, but it has lower sensitivity and resolution for honeycomb core-type sandwiches. Originality/value This study quantitatively compared the damage size indication capabilities of sandwich structures by using various NDT techniques. Results of the realised tests can be used for successful selection of a suitable NDT method. Combinations of the presented methods revealed most defects.

Application of different imaging techniques for the characterization of damage in fiber reinforced polymer

“…Due to simultaneous activation of different damage mechanisms and their interactions, the failure of laminated FRPs is a direct result of events occurring at microstructural levels [3]. This strong interconnection calls for advanced techniques for early detection of both damage initiation and monitoring damage growth, which is essential to assess the state of structures and their residual strength [4].…”

Assessment of Internal Damage in Sandwich Structures by Post-Processing of Mode Shapes Using Curvelet Transform

“…Recently, numerous non-destructive testing (NDT) techniques have been adapted to detect, localize, and identify surface and internal flaws in sandwich structures. These techniques, depending on the industrial conditions, in which a sandwich structure is operated, include visual testing [ 6 ], ultrasonic testing [ 7 , 8 , 9 ], thermography [ 10 , 11 ], eddy-current testing [ 12 ], shearography [ 7 ], guided waves-based techniques [ 1 , 13 , 14 ], electrical impedance [ 15 ], terahertz testing [ 16 ], etc. as well as by various embedded sensors in smart structures [ 17 ].…”