The EU-project EVITA (Non-Destructive EValuation, Inspection and Testing of Primary Aeronautical Composite Structures Using Phase Contrast X-Ray Imaging) aims at bringing Grating-based Phase Contrast X-ray imaging technology to Non-Destructive Evaluation and Inspection of advanced primary and/or complex aerospace composite structures. Grating-based Phase Contrast X-Ray Imaging is based on the so-called Talbot-Lau interferometer, which is made of the combination of a standard X-ray apparatus with three transmission gratings as documented in the literature. This paper presents a comparison of two traditional non-destructive techniques (NDT): ultrasonic through transmission (immersed and water jet) and ultrasonic phased-array pulse echo, with the developed phase contrast XRay Imaging applied to advanced aerospace carbon fibre reinforced polymer. Typical defects produced during manufacture is examined as part of the testing and validation procedure. The following defects have been identified as being those most likely to be detected more effectively by the Grating-based Phase Contrast X-Ray Imaging process than other state of the art industrial NDT techniques: porosity, foreign objects, cracks, resin rich, cut fibres, and wavy fibres. The introduction of this innovative methodology is expected to provide the aeronautical industry with a reliable and detailed insight of the integrity of thin and thick Appl Compos Mater (2017)
A combined analytical and numerical study of an isotropic cracked plate that was repaired by using a bonded composite patch was conducted. The analytical work was based on Rose's equations, whereas for the numerical investigation a three‐dimensional finite element analysis was implemented. A number of cracked plates with different crack lengths and overall dimensions of the composite repair were considered. The composite patch was made of unidirectional laminates with different stacking sequences. Both, one‐ and two‐sided patches were analysed. Results are presented for the stress intensity factor in the patched crack and the maximum stress reinforcement stress and adhesive strain. It was found that for the case of a two‐sided reinforcement the results obtained by both methods were in good agreement. However, for the case of a single reinforcement the accuracy of the analytical method decreased due to the tendency to out‐of‐plane bending as a result of bonding a reinforcing patch to only one face of a plate, which is ignored in the analysis.
The increasing demand for fatigue life extension of both military and civilian aircraft has led to advances in repair technology for cracked metallic structures. Conventional structural repairs may signi cantly degrade the aircraft fatigue life and lower its aerodynamic performance. Adhesively bonded composite reinforcement is a new technology of great importance due to the remarkable advantages obtained, such as mechanical ef ciency and repair time and cost reduction. In this article, bonded composite patch repairs were designed for quick application to aircraft under emergency conditions, such as aircraft battle damage repair (ABDR). A formulated method was developed, to be applied when damage has to be restored quickly, without restrictions to safety of ight. Different damage cases were investigated using nite-element analysis (FEA), taking into account speci c parameters of the structure under repair. Based on the FEA results, a quick design procedure using composite patch repairs for the most frequent damage cases is proposed.Current world economic conditions are forcing the operation of both military and civilian aircraft well beyond their original design life, resulting in innovative repair techniques. The recent development of high-strength bers and adhesives has led to the invention of a new methodology for the repair of metallic structures, by the adhesive bonding of patches manufactured of composite materials. Bonded repairs are mechanically ef cient, cost effective, and can be applied rapidly to produce an inspectable damage-tolerant repair [1 -3]. The actual objective of the repair of a cracked or corroded metallic structure by an adhesively bonded composite patch is, practically, the transfer of loads from one side of the material to the other, via the patch. Traditionally, structural problems due to fatigue or corrosion have been repaired by the addition of a metallic patch manufactured from aluminum or steel, which was mechanically joined to the cracked structure using fasteners or bolts. This kind of repair creates stress concentration areas in the vicinity of the fasteners, which may lead to further structural problems, such as reduction of the fatigue life of the structure. Moreover, the time required for the application of a mechanical repair
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