Papers by Keyword: Non-Destructive Technique

Abstract: During the last years, some concerns have arisen in relation to the outcome of mechanisms of failure in composite materials according to its mechanical behavior. Such interest resulted in the development of new complex structures in order to enhance its mechanical resistance and the controlling of damage processes. Nevertheless, it is imperative to understand the degree of mechanical performance that these materials can achieve when under external stresses. In this regard, applying Acoustic Emission (AE) technique is widely known as a very effective technology for identifying and monitoring damage progression on different kind of materials and structures providing valuable information. AE is a non-destructive technique (NDT) capable of detecting micro damage initiation and propagation along several types of failure modes such as reinforcement/matrix interfacial debonding, matrix cracking, delamination, fracture, etc. This paper examines applications of AE regarding to composite materials where fracture processes are generally more complex and data interpretation is correspondingly more difficult. Finally, in order to continuously improve the reliability of this technique, several researches have advanced its trustworthiness through innovations in AE technology. Some perspectives are discussed.

Abstract: Laminated composite structures are subjected to impact damage during maintenance and manufacturing operations and their life service. Driven by the necessity to value damage tolerance and durability of composite materials, an analysis of multi-hit impact is conducted to reproduce the real service conditions. Despite many studies in the literature investigated the properties of composites at low impact velocity, in contrast the behavior of the hybrid configuration, especially at repeated impacts, result still little known. This work presents an experimental and numerical study of the dynamic behavior at the repeated low-velocity impact of a carbon and glass fibers hybrid composite laminate.

Abstract: Eddy current as a non-destructive technique has been used for evaluation of thermal barrier coatings (TBCs) system. In this study the TBCs system which consists of substrate material of stainless steel 316, Ni-20Cr as a bond coat and top coat of CaZrO₃ was produced by air plasma spraying technique. Isothermal treatment of TBCs system was performed and its effect on the microstructures and oxide formation was investigated. The chromium oxide formation as a function of temperature and time was observed. The observed changes in microstructure and formation of chromium oxide were then correlated with variation in eddy current values.

Abstract: The aim of this review is to gain the informations on applications and approaches that are presently available for non-destructive techniques (NDT) in composite materials. This review also will enhanced the knowledge in the NDT fields with available studies theories and research works done currently. Thus, it has been concluded the research that have been done in the past for military purpose but nowadays (NDT) technique is widely used in other various applications including composite materials, fire safety, land determine, food safety and quality and also famously practice in medical used.

Abstract: In the present paper, a project for integrated investigation is described, using noninvasive methods, specially designed for dealing with the highly diversified historic heritage of Piedmont (Italy). The stability of the decorated surfaces will be investigated by innovative Acoustic Emission (AE) and ultrasonic methods already experimentally tested in the field of artistic and monumental cultural heritage in Italy. The ultrasonic investigation techniques allow assessing separations, defects and damage phenomena that can regard the decorated surfaces and the masonry supports. Innovative acoustic methods will allow distinguishing a well-preserved artwork in comparison to a damaged one providing a quantitative criterion for the definition of intervention priority.

Abstract: A nondestructive technique would be very beneficial, which could be used to test the CF/Epoxy composite laminates. A new method for nondestructively determining the ply layup in a composite laminate is presented. A one-sided pitch-catch setup was used in the detection and evaluation of flaws and material anomalies in the composite laminates. Two Rayleigh wave transducers were joined head-to-head and used in the pitch-catch mode on the surface of the composites. The pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave to subtle flaw conditions in the composite. Also the other method employs a normal-incidence longitudinal ultrasound to perform C-scan of ply interfaces of the laminate, and extracts fiber orientation information from the ultrasonic reflection in the laminate. Using two-dimensional spatial Fourier transform, interface C-scan images were transformed into quantitatively angular distribution plots to show the fiber orientation information therein and to determine the orientation of the ply. Therefore, it is found that the efficiency of developed system shows between the one-sided pitch-catch testing and C-scan images in characterizing ply-layup orientation of the laminates.

Abstract: A nondestructive technique would be very beneficial, which could be used to test the part before (uncured) and after curing CF/Epoxy. A new method for nondestructively determining the ply layup in a composite laminate is presented. The method employs a normal-incidence longitudinal ultrasound to perform C-scan of ply interfaces of the laminate, and extracts fiber orientation information from the ultrasonic reflection in the laminate. Using two-dimensional spatial Fourier transform, interface C-scan images were transformed into quantitatively angular distribution plots to show the fiber orientation information therein and to determine the orientation of the ply. In order to develop these methods into practical inspection tools, an automated system using a motor has been developed for different measurement modalities for acquiring ultrasonic effects of ply-layup error. Therefore, it is found that the efficiency of developed system shows between the practical testing and model in characterizing cured/uncured ply-layup error of the laminates. A C-scan image of a ply interface seem to have the ply-layup error information of the two neighboring plies of CF/Epoxy composite laminates.

Abstract: There is currently a need to evaluate the non-destructive techniques that are used to detect the fracture of stressed steel wires in grouted post-tensioned concrete bridges. Although continuous acoustic emission (AE) monitoring technique has been developed to detect wire breaks in unbonded tendons, it is not established as the on-site monitoring tools for grouted post-tensioned concrete bridges. In this study, AE measurements were conducted to detect corrosion-induced wire fractures inside a grouted post-tensioned beam. The test beam was drilled with 5mm drill bit to expose individual wires and a reservoir filled with corrosive solution of NaCl and NaOH was formed on the side of the beam. During the experiment, the corrosion site was anodically polarized to + 200mV using a potentiostat and it was continuously monitored and the data obtained were processed with an AE monitoring system. The outcome of this research shows that the continuous AE monitoring system successfully identified and located an individual corrosion-induced wire fracture in a fully grouted post-tensioned concrete beam.