The fault‐free fabrication of fiber‐reinforced plastics (FRPs) is a big hurdle for textile and composite manufacturers. Voids are generated during the infiltration process of FRPs, which then reduce the mechanical performance of FRPs. This paper describes the effect of defined amount of voids on the mechanical properties, such as tensile, bending, impact and inter‐laminar shear strength of FRPs. The defined amount of voids in carbon FRPs are produced by a newly developed process—mixing of a foaming agent with resin system during the infusion process. The utmost advantage of this process is simple, time‐saving and reproducible. The produced FRPs from this process can be utilized for the validation of ultrasonic testing of FRPs. Four types of FRPs with six carbon layers are fabricated by a vacuum assisted resin infusion process. Carbon fibers are chosen in this study because of their growing market potential. Then, the mechanical properties of the produced carbon FRPs are tested. Besides the mechanical testing, the microscopic testing and ultrasound testing is executed to qualitatively analyze the length and distribution of produced voids. Results reveal that the mechanical properties of carbon FRPs reduce by an increase in defined amount of voids. POLYM. COMPOS., 40:E1049–E1056, 2019. © 2018 Society of Plastics Engineers
Different signal processing and image reconstruction techniques are applied in ultrasonic non-destructive material evaluation. In recent years, rapid development in the fields of microelectronics and computer engineering lead to wide application of phased array systems. A new phased array technique, called "Sampling Phased Array" has been developed in Fraunhofer Institute for non-destructive testing. It realizes unique approach of measurement and processing of ultrasonic signals.The sampling phased array principle make use of the measurement of elementary waves generated by individual elements of sensor array to reconstruct the composite phased array signal for any arbitrary angle or focus depth. The use of special signal processing and image reconstruction algorithms, allows generating A-Scans of several angles and / or Sector-Scan, which can be implemented in real time. With parallel computing structures, this principle is used for automatic testing systems at very high inspection speed. A comparative study was done with Conventional Phased Array system and Sampling Phased Array technique. The study shows that the signal characteristics in both techniques are equal. In addition, the Sampling Phased Array technique is significantly beneficial in the many aspects like quality of information in specific cases, inspection speeds and adaptability to specific inspection tasks in comparison to conventional Phased Array. The electronics was developed as a development platform for high speed automated ultrasonic inspection systems for process integrated testing and also for testing of critical components. The development results, including relevant test methodology and electrotechnical/electronic aspects are presented in the current work.
Nowadays the problem of remote sensing of various objects and people to prevent transportation and storage of weapons, explosives, and other forbidden objects becomes urgent in connection with strengthening security measures on counteraction to terrorism all over the world. Methods based on x-ray, magnetic induction, and radar sensing are developed intensively. Methods of x-ray sensing, as a rule, are applied to lifeless objects; in some countries, irradiation of people even by low-power x-rays is forbidden. Methods based on application of magnetic fields are suitable for detecting metal objects; however, they are inapplicable for detecting dielectric targets such as explosives or ceramic knifes. Radio-wave methods are relatively safe for people and allow any objects, including dielectric ones, to be detected. For this reason, methods of micro-wave radar sensing are developed intensively all over the world
Different signal processing and image reconstruction techniques are applied in ultrasonic non-destructive material evaluation. In recent years, rapid development in the fields of microelectronics and computer engineering lead to wide application of phased array systems. A new phased array technique, called "Sampling Phased Array" has been developed in Fraunhofer Institute for non-destructive testing. It realizes unique approach of measurement and processing of ultrasonic signals.The sampling phased array principle make use of the measurement of elementary waves generated by individual elements of sensor array to reconstruct the composite phased array signal for any arbitrary angle or focus depth. The use of special signal processing and image reconstruction algorithms, allows generating A-Scans of several angles and / or Sector-Scan, which can be implemented in real time. With parallel computing structures, this principle is used for automatic testing systems at very high inspection speed. A comparative study was done with Conventional Phased Array system and Sampling Phased Array technique. The study shows that the signal characteristics in both techniques are equal. In addition, the Sampling Phased Array technique is significantly beneficial in the many aspects like quality of information in specific cases, inspection speeds and adaptability to specific inspection tasks in comparison to conventional Phased Array. The electronics was developed as a development platform for high speed automated ultrasonic inspection systems for process integrated testing and also for testing of critical components. The development results, including relevant test methodology and electrotechnical/electronic aspects are presented in the current work.
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