Fabrication,testing,and analysis of sandwich structure with composite skin and additive manufactured core

The mechanical behavior of a sandwich structure made of woven glass/epoxy skins and an additive manufactured (AM) core was studied. The AM core was fabricated using polyetherimide and fused deposition modeling. This combination was chosen to increase the out-of-plane strength of an AM aircraft part. Tensile, flexural, and puncture tests were conducted for both the AM core and sandwich structure. The behavior of the beams was governed by the skins; however, the effect of the AM core for one-sided beams was significant. The tensile strength predicted by the simple mixture rule was in good agreement with the experimental results. For the flexural test specimen, sandwich beams were tested under three-point bending. The addition of composite skins increased the elastic modulus and flexural strength in both directions. The prevalent failure modes were skin wrinkling and core failure, and failure of the compressive skin was more likely. Puncture tests were conducted at three different temperatures. Owing to the increased bending stiffness, the sandwich structure did not exhibit ductile-to-brittle transition behavior.