Pre-study of Determination of Elastic Modulus of Polymers and Glass Fiber Reinforced Polymers with Pulse-Echo Method Ultrasonic Testing

• Main Author: Zefanya S Tarigan - Nim: 13713015 , Tania
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/24469
• Institution: Institut Teknologi Bandung

Elastic modulus is one of mechanic properties of material that often used in industry or research field as a benchmark to determine materials’ performance to withstand load without being deformed. Destructive testing is perpetually used to determine this property. However, destructive testing needs sampel and in situ testing is implausible. Various types of material are used in production process of industry, e.g., polymers and composites. By principle, ultrasonic inspection, which depends on elastic property and density of materials, can be used to determine elastic modulus. <br /> <br /> <br /> Experiments are conducted on several types of polymers and glass fiber reinforced polymers with frequency and thickness as experiment parameters. Ultrasonic testings were conducted with GE USM 35X device, which is a contact method type of ultrasonic testing machine. With an input of specimens’ thickness, materials’ sound velocity (&#957;) could be obtained, thus results of &#957; were counted to attain the elastic modulus. Comparison between ultrasonic testing results and mechanical testing results of polymers’ elastic modulus, as well as ultrasonic testing results and micromechanics calculations of glass fiber reinforced polymers’ elastic modulus were performed to analyzed the data. <br /> <br /> <br /> In this research, elastic modulus value obtained from ultrasonic test has a profound error, especially for polymer with an eminently low density. Also, lower probe frequency ease the detection of alternating ultrasonic wave. Specimens’ thickness adjusted with near-field calculation can eliminate the near-field effect, which is a natural phenomenon of ultrasonic wave. However, it will not grant an acurate value because an excessive thickness will give an attenuation effect. For composite, elastic modulus value obtained from ultrasonic test has an even bigger error, compared to the micromechanic calculations and also unstable, especially for fiber reinforced polymer WR400, that is more anisotropy than fiber reinforced polymer CSM. This happened because ultrasonic wave detects the reinforcement as defect or as an opposite side of the samples. <br /> <br />