Young's Modulus Determination of Polyester and Epoxy by Means of Ultrasonic Pulse Echo Testing

The Young's modulus or elasticity modulus is material ability to resist elastic deformation when loaded. Thermosetting polymers have a wide range of modulus elasticity values. To determine the elasticity modulus value, materials need to be destructive tested, such as tensile test or bending test. But in industrial field, they avoided destructive test. Theoretically, the modulus of elasticity can also be determined by ultrasonic testing pulse echo method. This method has already applied successfully for metals material. The goal of this research was to evaluate probe used in longitudinal velocity measurement of polyester and epoxy and to determine Young's Modulus of polyester and epoxy by means ultrasonic pulse echo testing. This method was performed using three longitudinal probes that have different diameters, frequencies, and additional delay line. The specimens were varied with different thicknesses. The ultrasonic pulse echo method uses probe 3 with a diameter of 12.7mm, a frequency of 1.5MHz, and additional delay line is most suitable to measure the longitudinal velocity of polyester and epoxy with thickness of 2.82-36.72 mm. Probe 3 has a smaller diameter and additional delay lines thus eliminating the effect of dead zones. The elastic modulus error of thermoset polymer material through ultrasonic testing of pulse echo method compared to the mechanical modulus of elasticity is still very large, i.e. 102% for epoxy, and 159% for polyester. A large error is caused by attenuation and the use of the elasticity modulus equation from ultrasonic testing that still requires modification.