An Experimental Comparison for Compression of PLA Specimens Printed in In-Plane and Out-of-Plane Directions

Abstract

The present work proposes an experimental comparison between the in-plane and out-of-plane compressive behaviors of 3D printed PolyLactic Acid (PLA) specimens. These specimens are produced via the Fused Deposition Modeling (FDM) technique by using two different printing directions: the first printing direction in the xz plane allows experimental compression tests in the out-of-plane direction; the second printing direction in the xy plane allows experimental compression tests in the in-plane direction. The specimens are more rigid in the out-of-plane direction than in the in-plane direction. In the first case, a bigger linear compressive Young modulus has been found and both maximum stress and proportional limit stress were determined. In the second case, the linear compressive Young modulus is smaller and the specimens are less rigid but at the same time more resistant: in fact, no maximum stress and proportional limit stress have been obtained because the test machine has reached the maximum applicable load. This research demonstrates as the compressive behavior of 3D FDM printed polymeric elements depends on the printing and test directions and this feature is fundamental when such elements will be used for structural applications. The experimental tests performed in the present paper are accompanied by statistical and capability analyses for the dimensional parameters and for the mechanical properties in order to also evaluate the stability of the production process and the validity ranges for the mechanical characteristics.

Compression Strength of PLA Bolts Produced via FDM

“…However, the observed changes are not linear in nature. The recorded values differ 2-to 2.5-fold from those that can be found, for example, in [23,24]. Once again, this is most probably caused by the effect of the selected fill ratio.…”

“…The authors of [22] determined the value of this coefficient at approximately 1750 MPa, without registering any significant effect connected with flat and upright printing orientations (cylindrical sample of the diameter of 12.7 mm and height of 25.4 mm, with the compression velocity of 1.3 mm/min). Research described in [23], on the other hand, demonstrated compression modulus E c values of approximately 2578 MPa for out-of-plane compression tests and approximately 2029 MPa for in-plane compression tests (rectangular samples, base side length 12.7 mm, height 40 mm). These were similar to values determined in [24].…”