Determination of the type of anisotropy and stiffness tensor in additive manufacturing polymer components by using ultrasonic waves

Mechanical properties of engineering components are of importance in medical and industrial applications. Ultrasonic nondestructive testing is one of the most effective methods for assessing the elastic properties of materials. The purpose of this paper is to evaluate the elastic properties of components made by fused filament fabrication (FFF) additive manufacturing process by using ultrasonic waves. This is accomplished by fabricating a test specimen with a predetermined geometry from PLA polymer by FFF process. The ultrasonic wave velocity is then measured in this test specimen along different directions. The elastic coefficients of the specimen are then calculated from the measured wave velocities by assuming orthotropic structure for the specimen. The engineering elastic coefficients, such as Young's modulus, Poisson's ratio, and shear modulus are also found by inversing the elastic tensor. Considering that some of the measured elastic constants of this material were almost identical, the hexagonal that was simpler than orthotropic. Based on the results, it can be concluded that the sample has hexagonal anisotropy. The tensile testing results obtained from tensile samples made from the same material were compared with ultrasonic test results and were in agreement. Other acoustic properties of this material such as sound attenuation and acoustic impedance were also measured and discussed. It is concluded that the ultrasonic method is very efficient in measuring the elastic properties of polymer components manufactured by FFF process and can be used for determination of changes in elastic properties of the material due to variations in the process parameters.