Elastic modulus determination of random glass fiber-reinforced polyester composites using pulse-echo ultrasonic method

Abstract

Random glass fiber polymer composites are often used as structural components and chemical resistant reinforcement layer. These kinds of composites can be degraded by environmental interactions and workload, resulting in the decrement of elastic modulus which will lead to a structural failure. Elastic modulus represents the elastic properties of composites. Theoretically, elastic modulus value could be obtained by using ultrasonic pulse-echo technique. This experiment is conducted to determine elastic modulus of random glass fiber reinforced polyester composites by measuring the longitudinal velocities. Four different fiber volume fractions with different thicknesses were ultrasonic tested followed by a comparison to the analytical model. Additional delay transducer was used to hinder the nearfield effect. Attenuation factor were measured to consider its effect to the calculated elastic modulus. Results show that the use of pulse-echo ultrasonic method has been able to determine the anisotropy and the effect of fiber volume fraction to elastic modulus of random glass fiber-reinforced polyester composites. The calculated in-plane elastic modulus have errors up to 28% compared to the analytical model and higher fiber volume fraction produced higher sound velocity and greater wave attenuation.