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The purpose of this paper is to present a study on the application of four damage factors to several single and multiple damage scenarios of aluminium beams. Each one of these damage factors is defined by the information given by modal curvatures of the beams.

The methodology consisted of a first experimental stage in which the modal rotations were measured with shearography and a subsequent numerical analysis in order to obtain the modal curvatures. To this end, three finite difference formulae were applied. The modal curvatures were then used to calculate the damage factors.

It was found that the profile of the damage factors varies according to the finite difference formula used. In view of the findings, the differences among the damage factors analysed are highlighted and some final recommendations to improve damage identifications via modal curvature-based are presented.

To the best of the authors’ knowledge, the application and comparison of several finite difference formulae and corresponding optimal sampling has not been carried out before. With the proposed approach, it is possible to identify multiple damages, which is still a great challenge. The post-processing of shearography measurements with a numerical method, which is inherently a multidisciplinary approach, is also a substantial improvement upon other type of approaches found in the literature.

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.

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).

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.

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.

The purpose of this paper is to provide an insight into the techniques used for the non‐destructive testing (NDT) of non‐metallic structural materials, notably polymer and ceramic composites.

Following a short introduction, this paper first considers methods for testing carbon fibre‐ and glass fibre‐reinforced polymer composites. It then discusses the role of NDT in wind and wave power systems and some of the techniques used to test ceramics and ceramic composites. Brief conclusions are drawn.

This shows that the growing use of non‐metallic engineering materials in critical applications has highlighted the need for a range of advanced NDT methods. While some traditional techniques can be adapted to test these materials, in several instances novel methods are required. These include a range of thermal, ultrasonic, electromagnetic, radiographic and laser‐based technologies.

The paper provides a review of the techniques used and being developed for the non‐destructive testing of non‐metallic engineering materials.

Various types of damage or cracking in the structural components of an airframe can occur during the service lifetimes of aging aircraft. These types of damage are commonly repaired with a patch that can be joined to the original structure by different techniques, e.g., riveting and bonding. The purpose of this paper is to describe the repair of a fatigue crack in the metallic wing structure of a jet trainer aircraft using an adhesively bonded boron composite patch.

The partial analytical design and numerical analysis of the repair is presented. Three different versions of the patch are quantitatively investigated. The efficiency of the designed adhesively bonded boron patch with the parent metallic structure is experimentally verified by panel tests, and two different patch geometries and two surface preparation techniques are investigated. The panels were designed, manufactured and tested as representative structures of the repaired structure.

Adhesively bonded composite repair increases the lifetime by at least one order compared with the non-repaired structure. Both surface preparations provide equivalent results. The repair lifetime is significantly influenced by the patch geometry, and the longer patch significantly increases the lifetime of the panel. The lifetime of the structure can be increased by ˜40-fold if the patch geometry is a rectangle with 1:1.5 proportions of the sides (length in the crack direction/length perpendicular to the crack propagation). The patch length in the crack direction should be twice that of the initial crack length. Additional patch length extension in the direction that is perpendicular to the crack propagation does not appear to be effective for significantly decreasing the stress intensity factor and patch efficiency. The repair also retards the crack propagation if the crack grows out of the patch. No significant disbonding was detected.

The work described in this paper provides information that is very useful for patch design and verification with relation to different patch geometries and technologies. The designed and verified repair has been successfully applied to an L-39 Czech aircraft structure.