Optical infrared thermography of CFRP with artificial defects : performance of various post-processing techniques

This paper treats an experimental study that focusses on optical infrared thermography for non-destructive testing of composites through lock-in and flash excitation. Different fiber reinforced plastics with various artificial defects have been investigated. Three different postprocessing techniques are applied, namely fast Fourier transform (FFT), principal component analysis (PCA) and thermographic signal reconstruction (TSR). A comparison between the different excitation and post-processing methods is performed, and their strengths and weaknesses in detecting artificial defects in composites are evaluated and discussed

Non-Destructive Testing of Carbon Fiber Crank Arms

Carbon fiber components present unique challenges for detecting defects, damage, and fatigue. Nondestructive methods exist for testing and locating defects. However, most of these methods are expensive, not versatile enough for practical use on non-idealized parts, or both. Vibrothermography can be an affordable option and has shown promising results with thin rectangular panels. The goal of this senior project was to assess the feasibility of using vibrothermography to find defects in SRAM carbon fiber crank arms. Our team found vibrothermography to be a feasible method of non-destructive testing for carbon fiber crank arms, and this report discusses the development and implementation of the necessary theory, fixturing, and testing procedures

Adaptive spectral band integration in flash thermography : enhanced defect detectability and quantification in composites

In flash thermography, the maximum inspectable defect depth is limited when only the raw thermographic sequence is analyzed. The introduction of pulsed phase thermography (PPT), in which phase (contrast) images at different thermal wave frequencies are obtained, significantly improved the maximum inspectable depth while reducing the effects of non-uniform heating and non-uniform surface properties. However, in a practical environment, the evaluation of many phase images per inspection is a cumbersome procedure. In this paper, a novel Adaptive Spectral Band Integration (ASBI) procedure is introduced for the post-processing of flash thermographic datasets, which yields a unique damage index map. ASBI integrates the most useful spectral information for each pixel individually, obtaining a maximized defect detectability and an almost zero-reference level. The performance of ASBI with respect to defect detectability as well as defect sizing and depth inversion is evaluated thoroughly with both experimentally and numerically generated datasets. The ASBI procedure is successfully applied on various composite coupons with flat bottom holes and barely visible impact damage, as well as on a stiffened aircraft composite panel with a complex cluster of production defects. The ASBI procedure is compared with existing data-processing techniques in literature, illustrating an enhanced performance

Effect of Poisson’s Ratio on Young\u27s Modulus Characterization Using Ultrasonic Technique by Modeling

The past 27 years has witnessed a revolutionary growth in the progress of material development and application in almost all industry and business sectors, and this seems to be continuing even today. So many material-driven innovations have enabled the global spread in technology and improvements in capability, ranging from communications to aerospace and healthcare, to automotive and agriculture. Mechanical behavior of elastic materials is modeled by two main independent constants; Young’s modulus and Poisson’s ratio. An accurate measurement of both constants is necessary in most engineering applications, for example, the standard materials used for the calibration of some equipment, quality control of other mechanical materials. In this work, 7075-T6 Aluminum and carbon fiber-epoxy composite were used to study the effect of change in Poisson’s ratio on the Young’s modulus of a material using non-destructive testing (NDT). Ultrasonic simulation was used because Lamb wave velocity is dependent on the elastic properties of the transmission medium. Also, ultrasonic simulation shows more accuracy and non-destructive advantages over the tensile and indentation test. The theoretical and experimental results were used to validate the results of simulation before using it for this study. ‘ANSYS mechanical’ software was used to simulate the process

Spot weld inspections using active thermography

Spot welds have a significant part in the creation of automotive vehicles. Since the integrity of, for example, a car, is dependent on the performance of multiple welds, it is important to ensure the quality of each spot weld. Several attempts have been made in order to determine the quality of spot welds, but most of them do not focus on the applicability in the manufacturing process. Spot weld inspections are often performed using back heating. However, during manufacturing, robotic inspections are desired, and since the bodywork of a car is a complex shape, the accessibility from the inside of the vehicle is minor. Therefore, inspections using front heating are more suitable. In this manuscript, multiple excitation methods are compared as well as different post-processing techniques. The used excitation techniques can be divided into light heating and inductive heating. Light heating is further divided in lock-in thermography and pulse thermography. The used post-processing techniques are principle component analysis and fast Fourier transform. Inductive heating turns out to be the most suitable measurement technique since it is fast and can be performed as front and back heating. Both investigated post-processing techniques deliver suitable information, such as relief images and information of the internal structure of the spot wel

Non-destructive examination of ceramic matrix composites for quantitative determination of porosity via pulse-echo thermographic inspection

Ceramic Matrix Composites are seeing a widespread increase in use, especially in the aerospace industry. These materials are being utilized for their excellent material properties at high temperatures. As these materials are used in jet engine components and proposed as the skins of hypersonic vehicles, the consequences of material failure can be catastrophic. As-manufactured porosity is one of the earliest indicators of sub-optimal material properties that would lead to premature failure. Non-Destructive Testing methods have long been utilized for the examination of more “traditional” composite materials. This investigation discusses the use of several NDT methods on CMCs and the advantages and limitations of those inspection methods, with a particular focus on the determination of sample porosity. Pulse-Echo Flash Thermographic Inspection is of particular focus, while Film Radiography and Computed Tomography are also examined. Derived equations are examined for Film Radiography and Flash Thermography to determine their accuracy in calculating porosity from raw data. While Film Radiography did not yield a suitable equation, Flash Thermographic results yielded an equation which allowed for calculation of the sample porosity using only the raw data and known sample thickness. This equation was partially validated using results from additional sample sets. The additional limitations and artifacts of Flash Thermography are examined to show the ways in which the inspection method is limited. Examinations of representative aircraft components, manufactured of CMC material, also provided realistic defects and integrated components that were located by and had varying effects on the Flash Thermographic Inspection

3D Printed Carbon Fiber Electric Mountain Bike Frame

3D printing of carbon fiber composites has been a developing technology for about 5 years, and in this time, Arevo Labs has established itself as a leader in the field. Our team joined forces with Arevo, who sponsored our project as we showcased their new, innovative carbon fiber manufacturing process. To do so, we focused on the conceptual design, analysis, assembly, and material testing of an electric mountain-bike frame printed with Arevo’s continuous carbon fiber printing technology. Our bike consists of the main frame and a chain stay subsystem, which connects the rear wheel to the rest of the frame and interfaces with a suspension system. Understanding how the capabilities of the printer, the properties of the materials, and the typical loading scenarios experienced by mountain bikes all worked together was paramount in analysis, simulation, and design optimization and iteration. Thus, the focus of this project is to design a mountain bike capable of withstanding typical loading patterns with a high level of safety. Further, the team aimed to optimize a bike frame which used the minimal amount of material necessary to reduce weight and cost for the user

Composites for hydraulic structures: a review

Composites for hydraulic structures: a review Composites have evolved over the years and are making major in-roads into the marine, aviation and other industries where corrosions and self-weight are the major impediments to advancing the state-of-the-art. Civil Works engineers have been reluctant to make use of these composite advantages, partially because of the absence of well documented success stories, accepted design and construction practices or specifications, and limited understanding of composites, higher initial costs and others. A few navigational structures using FRP composites have been designed, manufactured and installed in the United States of America and Netherlands, recently. US Army Corps of Engineers is embarking on higher volume applications of composites for navigational structures. This report is aimed at summarizing the state of the art of fiber reinforced polymer (FRP) composites for hydraulic structures including design, construction, evaluation and repair. After a brief review of history and introduction of fundamentals of composites, their manufacturing techniques, properties, and recent field applications are presented, including FRP rebar for bridge decks, other highway and railway structures, gratings, underground storage tank, pavement, sheet and pipe piling, FRP wraps, moveable bridges, utility poles, etc. Focus is placed on applications of composites in waterfront, marine, navigational structures including lock doors, gates, and protection systems. Design of hydraulic composite structures is presented for the cases available, such as design of FRP recess panel, Wicket Gates, Miter Gates, FRP slides and repair of corroded steel piles. This report also reviews engineering science issues such as fracture and fatigue, durability, creep and relaxation, UV degradation, impact resistance, and fire performance. The report concludes with summary remarks and recommendations after a discussion on operation and maintenance guidance including nondestructive evaluation inspection techniques. Intention is to provide up to date information on composite design, manufacturing and evaluation methodologies that are applicable for fabrication and maintenance of navigational structures. This report is a living document with advances taking place with time as waterborne transport infrastructure community makes progress with FRP systems. This report is expected to be useful for those decision-makers in government, consultants, designers, contractors, maintenance and rehab engineers whose focus is to minimize traffic interruptions while maximizing cost effectiveness

Active thermography for the investigation of corrosion in steel surfaces

The present work aims at developing an experimental methodology for the analysis of corrosion phenomena of steel surfaces by means of Active Thermography (AT), in reflexion configuration (RC). The peculiarity of this AT approach consists in exciting by means of a laser source the sound surface of the specimens and acquiring the thermal signal on the same surface, instead of the corroded one: the thermal signal is then composed by the reflection of the thermal wave reflected by the corroded surface. This procedure aims at investigating internal corroded surfaces like in vessels, piping, carters etc. Thermal tests were performed in Step Heating and Lock-In conditions, by varying excitation parameters (power, time, number of pulse, ….) to improve the experimental set up. Surface thermal profiles were acquired by an IR thermocamera and means of salt spray testing; at set time intervals the specimens were investigated by means of AT. Each duration corresponded to a surface damage entity and to a variation in the thermal response. Thermal responses of corroded specimens were related to the corresponding corrosion level, referring to a reference specimen without corrosion. The entity of corrosion was also verified by a metallographic optical microscope to measure the thickness variation of the specimens

Wings in Orbit: Scientific and Engineering Legacies of the Space Shuttle, 1971-2010

The Space Shuttle is an engineering marvel perhaps only exceeded by the station itself. The shuttle was based on the technology of the 1960s and early 1970s. It had to overcome significant challenges to make it reusable. Perhaps the greatest challenges were the main engines and the Thermal Protection System. The program has seen terrible tragedy in its 3 decades of operation, yet it has also seen marvelous success. One of the most notable successes is the Hubble Space Telescope, a program that would have been a failure without the shuttle's capability to rendezvous, capture, repair, as well as upgrade. Now Hubble is a shining example of success admired by people around the world. As the program comes to a close, it is important to capture the legacy of the shuttle for future generations. That is what "Wings In Orbit" does for space fans, students, engineers, and scientists. This book, written by the men and women who made the program possible, will serve as an excellent reference for building future space vehicles. We are proud to have played a small part in making it happen. Our journey to document the scientific and engineering accomplishments of this magnificent winged vehicle began with an audacious proposal: to capture the passion of those who devoted their energies to its success while answering the question "What are the most significant accomplishments?" of the longestoperating human spaceflight program in our nation s history. This is intended to be an honest, accurate, and easily understandable account of the research and innovation accomplished during the era