DETERMINATION OF THE MODULUS OF ELASTICITY OF WOVEN GLASS-POLYESTER COMPOSITES IN THE 45° DIRECTION BY PULSE-ECHO ULTRASONIC METHOD

• Main Author: Tulus Ikhsan Nasution, M
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/71237
• Institution: Institut Teknologi Bandung

The modulus of elasticity of glass fiber-reinforced polymer composites is generally determined through tensile testing. However, this method can damage the composite and cannot be applied in-situ. The modulus of elasticity of the composite can be determined without damage through ultrasonic testing using the pulse-echo method with 90? probe. Ultrasonic waves with 90° probe only propagate on the surface and sub-surface. Composite manufacturing with the Wet Hand Lay Up method can produce structural differences in the composite surface. Herein, this work determines the tensile modulus of woven glass fiber-reinforced polyester composites in the 45° direction and examines the limitations of using a 90° probe in determining the tensile modulus of composites with different structures. The tests are carried out using the ultrasonic pulse-echo probe method at 90° on the surface of composites with variations in fiber fractions of 38%, 41%, and 46% in the direction of 0°, 45°, 90°, and thickness. The microstructure, fiber content, and surface area of the composites are characterized using image analysis method. The elastic modulus of the ultrasonic test results is compared with the law of mixing. The results reveal that the modulus of elasticity of the glass-polyester fiber woven composite in the 45° direction can be determined by the 90° ultrasonic pulse-echo probe method. The modulus of elasticity in the 45? direction is up to 23% lower than that of 0? and 90? directions and up to 26% greater than in the thickness direction. The elastic modulus of the ultrasonic test results is aligned with the literature and the law of mixing. Overall, ultrasonic testing with the pulse-echo method using a 90° probe can determine differences of the modulus of elasticity in the surface of the composite with different fiber contents to a certain depth. Moreover, it confirms the limitations of using a 90° probe in determining the elastic modulus of the composite.