Non-destructive Testing Of Composites Research Articles

Model of fractured medium and nondestructive control of composite materials

Non-destructive testing of composites is an important issue in the modern aircraft industry. Composites are susceptible to the barely visible impact damage which can affect the residual strength of the material and occurs both during production and operation. The continuum model for describing the damaged zone is presented. The slip theory relations used for a continuous distribution of slip planes are applied. At the initial stage, the isotropic background model is used. This model allows the material slippage along the fractures based on the Coulomb friction law with the small viscous addition. In this regime, the govern system of equations becomes rigid. To overcome this difficulty, the explicit–implicit grid-characteristic scheme is proposed. The standard ultrasound diagnostic procedure of damaged composite materials is successfully simulated. Compared with the trivial free-surface fracture model, different reactions on the compression and stretch waves are registered. This approach provided an effective way for the simulation of complex dynamic behavior of damage zones.

Innovative 3D-Printed Tools Revolutionizing Composite Non-destructive Testing Manufacturing

Innovative 3D-Printed Tools Revolutionizing Composite Non-destructive Testing Manufacturing

High frequency eddy current inspection of fibre placement in Carbon Fibre Reinforced Polymer Composites

This paper presents experimental and simulation studies of high frequency eddy current non-destructive testing (NDT) methods for inspection of carbon fibre reinforced polymer (CFRP) composites. It is well known that CFRP composite materials are widely used in industry as structural components, and products based on such materials are increasingly developed and introduced to market. In recent years, non-conventional eddy current method operating at high frequencies for NDT of composites begins to attract attention. It provides a non-contact, couplant-free option of inspection when compared with the other NDT methods currently used in industry. As eddy current relies on fibre fabrics in individual plies to form the current pathways, the eddy current paths in composite are unsurprisingly complex due to the structural features of composite laminates when compared with that in homogenous conducting metals for which conventional eddy current NDT is often used in industry. It will be noted that the knowledge is still limited so far about the eddy current distributions in composite laminates due to lack of effective theoretical and numerical models. This paper will focus on the development of a new numerical model that is suitable for use in simulations of high frequency eddy current inspection of fibre placements. An effective model is desirable for understanding the performance dependence of the eddy current testing method on the material properties, composite structural features, and other parameters involved. In this model, the fibre tow layout of individual plies is taken into consideration. The collection of the pickup signals by the sensor probe shows clear images of the fibre placement in different layers. The simulation results are compared with experimental results of fibre placement imaging. The model is useful for understanding the physical process for inspection of composites using high frequency eddy current methods, and for studying the influence of the controllable parameters involved.

Research on laser ultrasonic propagation characteristics and quantitative detection of delamination of carbon fiber composite

Aiming at the problems of low signal-to-noise ratio (SNR) and low detection accuracy in the non-destructive testing of composites with anisotropic and multilayer structure, the delamination detection of composite materials is studied by using the advantages of laser ultrasonic micro defect detection combined with phased array technology. Firstly, through finite element simulation, the propagation characteristics of laser ultrasound when the delamination evolves are obtained, and a time-modulated phased array laser ultrasound test platform is designed to improve the SNR and detection efficiency of the delamination signal. Then, a laser ultrasonic feature extraction method based on the improved Hilbert-Huang transform is proposed. It includes optimizing the decomposition process of CEEMDAN (Complete Ensemble Empirical Mode Decomposition with Adaptive Noise), searching for the sensitive IMF components through correlation coefficient between the decomposed signal and the original signal, and extracting the feature parameters by Hilbert transform. Finally, the maximum amplitude imaging of the delamination defects is performed using the extracted feature parameters. Experiments show that the proposed method can characterize the delamination characteristics with high accuracy, effectively solve the interference of resin layer on the delamination characteristic signal, and can visualize the delamination in composites.

Tensor integrated total variation regularization for thermography NDT of composites

The carbon fiber reinforced polymer (CFRP) is being used frequently in the manufacturing of aerospace, rail, and other mechanical structures, where the optical pulse thermography (OPT)-based non-destructive testing (NDT) is generally used for the quality inspection, However, the output thermal sequences in OPT-based inspection suffer from uneven illumination and high-frequency thermal noise. Consequently, the inspection of defects (debonds) becomes difficult. To remedy it, post-image processing algorithms are generally carried out. The usefulness of such algorithms, however, is limited by the shape-complexity of the CFRP specimen. In this paper, we propose a tensor nuclear norm (TNN)-based low-rank and sparse total variation regularization (TVR) for CFRP debond defect detection. The integrated low-rank and sparse components are jointly and iteratively optimized. The proposed algorithm removes noise and segments/extracts the defects information from the thermal video sequences with improved resolution and contrast. Compared to the general image processing algorithm used for OPT-based NDT testing, the proposed algorithm is faster and in terms of F-score is more accurate.

Flat Inkjet‐Printed Copper Induction Coils for Magnetostrictive Structural Health Monitoring: A Comparison with Bulk Air Coils and an anisotropic magnetoresistive sensor (AMR) Sensor

Structural health monitoring (SHM) represents the next generation of carbon fiber‐reinforced composite nondestructive testing. One challenge facing the application of magnetostrictive SHM is the lightweighting and ease of installation of actuators and sensors. Inkjet printing (IJP) technology is well suited to produce miniaturized electronic induction sensors that can be paired with magnetostrictive actuators to detect strain. These sensors have several advantages: their thicknesses can be minimized, the surface area can be maximized to increase sensitivity, and complex multifilar coil configurations can be fabricated. A parametric study of the efficacy of IJP induction coils with different parameters (number of coils, monofilar/bifilar, size) tested on a number of actuator‐functionalized composite coupons (FeSiB ribbon and impregnated epoxy sensors) is conducted. The samples are characterized by measuring their inductance response through induced strains. Increased sensitivity and accuracy of the 10‐turn monofilar IJP sensor are shown with respect to 1) 70‐turn hand‐wound coils, 2) a three‐axis AMR sensor, and 3) other IJP actuators with <10 turns. This is attributed to increased contact area to the composite surface and the requirement of minimum sensitivity (i.e., the number of turns and surface area) for strain detection.

Non-destructive testing of light armours of CFRP after ballistic impacts by IR thermography methods

Multi-layered composites are frequently used in many military applications as constructional materials and light armours protecting personnel and armament against fragments and bullets. One of the many methods used in non-destructive testing of composites is active infrared thermography. In active thermography it is necessary to deliver energy to the examined sample in order to obtain significant temperature differences indicating the presence of subsurface anomalies. To detect possible defects in composite materials different methods of thermal stimulation can be applied to the tested material, these include heating lamps, lasers, eddy currents, microwaves or ultrasounds. The use of a suitable source of thermal stimulation on the test material can have a decisive influence on the detection or failure to detect defects. Non-destructive testing was carried out using the following sources of thermal stimulation, heating lamp, flash lamp, ultrasound and eddy currents. The paper presents the possibility of applying IR thermography methods for detecting defects in ballistic covers made of carbon fiber reinforced composites used in the construction of military vehicles.

Numerical Modeling of Ultrasound Phased Array for Non-destructive Testing of Composites

Ulrasound transducers with phased arrays are used in multiple areas, including medical and technical applications. The numerical modeling of the composite ultrasound requires high spatial and temporal resolution with a full viscoelastic anisotropic material model. The grid-characteristic method that can provide it is demanding in terms of calculation time. A problem of optimal adjusting of the phased array requires a fast and effective numerical method. The retracing method for acoustics that is used for ultrasound and seismic problems, improved with a wavefront construction method was implemented. A technique of modeling the ultrasound of composites with good accuracy and in a reasonable time is proposed.

Defect Estimation in Non-Destructive Testing of Composites by Ultrasonic Guided Waves and Image Processing

The estimation of the size and location of defects in multi-layered composite structures by ultrasonic non-destructive testing using guided waves has attracted the attention of researchers for the last few decades. Although extensive signal processing techniques are available, there are only a few studies available based on image processing of the ultrasonic B-scan image to extract the size and location of defects via the process of ultrasonic non-destructive testing. This work presents an image processing technique for ultrasonic B-scan images to improve the estimation of the location and size of disbond-type defects in glass fiber-reinforced plastic materials with 25-mm and 51-mm diameters. The sample is a segment of a wind turbine blade with a variable thickness ranging from 3 to 24 mm. The experiment is performed by using a low-frequency ultrasonic system and a pair of contact-type piezoceramic transducers kept apart by a 50-mm distance and embedded on a moving mechanical panel. The B-scan image acquired by the ultrasonic pitch-catch technique is denoised by utilizing features of two-dimensional discrete wavelet transform. Thereafter, the normalized pixel densities are compared along the scanned distance on the region of interest of the image, and a −3 dB threshold is applied to the locations and sizes the defects in the spatial domain.

Research on Eddy-Current Testing of Functional Polymer Composite Material

Eddy current testing method can be used to realize the noncontact measurements for mechanical quantities, material testing and flaw detection which made of conductive material (e.g., metallic material, carbon fiber reinforced polymer material and so on) [1], [2]. Therefore, electromagnetic nondestructive method have rarely used in functional applications, such as electro-magnetic interference shielding and absorbing material. Nowadays, the coating of shielding and absorbing material is widely used by specific conductive material which made of polymer composite material mixed with conductive particles. The insulating matrix of polymer composite material is separated by nanoscale conductive filler particles. Recently, the experimental results on the lift-off effect show that the induced voltage of the coil with alternating current changes regularly with the variations in the distance between the coil and the composite object. This phenomenon indicates that there exists an eddy current composed of the tunnelling current and the conduction current in the composite object. The results indicate that eddy current testing method has the potential to apply specific conductive polymer composite non-destructive testing.

Numerical Modeling of Non-destructive Testing of Composites

Low-velocity strikes are considered as one of the most dangerous load types for composites, especially in aviation. They do not lead to an immediate destruction of a whole detail, but inner damage, provoking a delamination between layers or between fiber and matrix, lowers the material strength and may cause a destruction during the flight. This inner damage can only be noticed via complex study, which increases an exploitation cost. Numerical modeling can help to interpret the results obtained from common portable devices, which are currently used for metals. The modification of known methodology can be reliably used for composites. In this research, a hybrid grid-characteristic method of 1-2 order on irregular tetrahedral grid is used. A carbon fiber polymer matrix of unidirectional composite is modeled as a homogeneous orthotropic media with a single distinguished direction along the fiber. As a result, the one-dimensional graphics, which correspond to A-scans in real devices, were obtained. The detailed analysis of received data confirms a rationality of proposed methodoly.

A review of non-destructive testing methods of composite materials

A review provided about non-destructive testing (NDT) methods for the evaluation of composites. The review considers the capabilities of most common methods in composite NDT applications such as Visual Testing (VT or VI), Ultrasonic Testing (UT), Thermography, Radiographic Testing (RT), Electromagnetic Testing (ET), Acoustic Emission (AE), and Shearography Testing with respect to advantages and disadvantages of these methods. Then, methods categorized based on their intrinsic characteristics and their applications.

Composite Nondestructive Testing Technology

The article introduces a variety of composite nondestructive testing technology which are new developed or commonly used in engineering in recent years, including the principle, detection range, characteristics and limitations. Make an outlook for the development directions of composite nondestructive testing technology.

Automatic evaluation of non-destructive testing of composites

Automatic evaluation of non-destructive testing of composites

In Introductory Review to THz Non-Destructive Testing of Composite Mater

As the volume of composite parts continues to rise, quality and performance specifications are becoming more and more demanding. In this context, robust and reliable nondestructive testing (NDT) techniques are necessary. Thanks to numerous recent technological breakthroughs in the THz field, the THz technology has proven to be a highly promising technology for composite NDT inspection. In this introductory review, the most relevant aspects of the THz technology as a tool for NDT inspection of composite materials are synthesized and analyzed based on a comprehensive review of the current literature. To this end, available THz experimental setups are described. Furthermore, THz imaging techniques suitable for composite inspection are analyzed and the THz spectroscopic approach is briefly presented. Finally, a review of the state of the art of THz based composite inspection systems is presented describing and analyzing recent most relevant milestones achieved in the field.

Stress Wave Propagation Discipline and Simulation Analysis in Non-Homogeneous Laminated Composites

Application of stress wave testing methods can realize non-destructive testing of composites, but non-homogeneous characteristics of composites determine the complexity of stress wave propagation. Using the stress wave theory to explain the propagation principle, to describe the stress situation in the composites, which is meaningful to perfect the stress wave testing method. In this paper, stress wave propagation principle of non-homogeneous laminated composites has been revealed, mathematical descriptions of stress wave propagation are also given, and finite element simulation method has been used to verify the theory.

NDT – checking the quality of the quality checker

George Marsh takes a look at the non-destructive testing of composites at the UK's NDT Validation Centre.

Contrôle non destructif de matériaux composites par la technique des courants de foucault : une nouvelle approche

Quality testing of composite materials is regularly carried out using non-destructive testing (NDT) techniques such as ultrasound, radiography or infrared thermography. However, these techniques present some limitations for the NDT of composites in terms of accuracy, sensitivity, repeatability of the signal and sometimes difficulty of calibration. In this article, it is demonstrated that eddy current testing, once solely dedicated for NDT of metallic materials, can also be adapted for the examination of composite materials. Indeed, this technique appears to be adequate for the detection and the characterisation of major flaws such as delamination and impact. A good reproducibility of the signals has been observed and this technique may become an efficient and low cost alternative compared to more complex and expensive techniques. Experimental results are shown and analysed and the advantages and limitations of eddy current testing of composite materials are discussed.

Non-destructive testing of aerospace composite materials using digital shearography

Digital shearography, a laser interferometry technique in conjunction with the digital imaging processing, has the potential for identifying defects both in small- and large-scale structures. This paper will focus on the recent development of digital shearography for non-destructive testing (NDT). With the improvement of the measuring methods and the development of a small and mobile measuring device in conjunction with a user-guided program, Shearwin, this laser inspection technique can be used easily in the environment of fieldwork. A few examples show its application in the aerospace industry for NDT of composites, e.g. GLARE panel, honeycomb structure and glass (or carbon)-fibre-reinforced plastics, etc.

Specialized techniques in holographic non-destructive testing of composites

Holographic interferometry is a very efficient technique used in non-destructive testing and characterizing of composites. Many kinds of defects may be simultaneously detected over large areas, without any contact with the tested material. All the defects appear as local distortions of a regular fringe pattern covering the holographic image of the tested object. Seeing a complicated fringe pattern with a large number of local distortions in a single image might be confusing for the operator, who is often interested in detecting a particular type of defect. In such cases, in order to apply the holographic technique, specialized testing techniques have to be established. This paper describes two such techniques, one for testing the metallic insertions in the belt area of rubber tyres, the other for testing pasteboard-epoxy composites, and detecting fiber direction and interactions.