Experimental and Numerical Analysis of the Vibration Behavior of a Bio-Based Sandwich with an Auxetic Core in a Humid Environment

Water absorption and vibration issues are major concerns for manufacturers and researchers using bio-based composites. In light of this, this work examines how water aging affects the dynamic characteristics of a sandwich with a reentrant auxetic core. The material considered to manufacture the specimens is polylactic acid (PLA) reinforced with flax fibers. It is manufactured using 3D printing which proceeds by adding layers successively. For various immersion times, the impact of water absorption on the dynamic characteristics is examined. Water aging obviously affects equivalent stiffness and damping. We therefore observe a decrease in rigidity and an increase in damping. These results could be explained by the plasticizing effect of water on bio-based composites, stimulated by water absorption as well as by the architecture of the core of the sandwich. Finally, a numerical strategy based on the finite element technique is developed. It made it possible to evaluate the equivalent rigidity and the damping for different immersion times. The results of this approach are in close agreement with those obtained experimentally.