Experimental and Numerical Investigation into Free Vibration of Delaminated 3D-Printed PLA Beams

The biodegradable Polylactic acid (PLA), is a versatile thermoplastic polymer and one of the most eco-friendly materials widely adopted and used as the feedstock for 3D printing and manufacturing of elements used in various fields such as healthcare, textile, packaging, bio-medical devices, to name a few. PLA is also used in bio-composite materials. Research is being made for the low-cost application of PLA in the aerospace industry. With the exponential growth of 3D printing applications, characterization of the filaments, used as the feedstocks, and the printed parts is essential for determining quality, controlling manufacturing processes, and making accurate model predictions of process and product performance. In this research project, the flexural vibration analysis and con-tact analysis of the 3D-printed PLA beam specimens will be conducted.
Experimental and FEM-based numerical free vibration analyses of defective 3D-printed PLA cantilever beam specimens are presented. The experimental setup and PLA specimens are briefly discussed. Experimental fundamental frequency results for defective, cantilevered, PLA beam specimens are evaluated, and average fundamental flexural (bending) frequencies are reported. The defect is considered to be a single, symmetric, through-the-width, centrally located, delamination of various thicknesses, covering one-third of the beam specimens’ length. The average frequency values are calculated based on three different trials, conducted to ensure the accuracy of the obtained results.
Numerical results, including fundamental frequencies and corresponding mode shapes, obtained through simulations carried out using Finite Element Analysis (FEA) Software (Femap with NX Nastran) are also reported and discussed. The comparison is made between the numerical (FEM) and experimental results. It is observed that the natural frequency drops for a small-thickness delamination (e.g., 0.1 mm), associated with the reduction in the flexural rigidity of the beam while the mass remains virtually unchanged. However, when the delamination thickness is further increased, the system natural frequency increases. This can be explained by the fact that while, in this case, the system’s flexural rigidity and mass both lessen, with latter decreasing more significantly than the former. As a result, the system’s natural frequency increases with growing delamination thickness.