Flexural response of 3D printed sandwich composite

Among many lightweight materials used in marine applications, sandwich structures with syntactic foam core are promising because of lower water uptake in foam core amid face-sheets damage. HDPE (high-density polyethylene) filament is used to 3D print sandwich skin, and glass microballoon (GMB) reinforced HDPE syntactic foam filaments are used for the core. The optimized parameters are used to prepare blends of 20, 40, and 60 vol % of GMB in HDPE. These foamed blends are extruded in filament form to be subsequently used in commercially available fused filament fabrication (FFF) based 3D printers. The defect-free syntactic foam core sandwich composites are 3D printed all at once (skin-core-skin printing in sequence at once) using optimized printing parameters and characterized for the flexural behavior. The result reveals that the addition of GMB increases both specific modulus and strength in sandwich composites and is highest for the sandwich having a core with 60 vol% of GMB. The measured properties of sandwiches are compared with a respective core to study the effect of the sandwich. It is observed that flexural strength, fracture strength, and strain of foam core sandwiches registered superior response than their respective cores. The experimental results are found in good agreement with theoretical predictions. Finally, the failure mode of the printed sandwich is also discussed, and it is observed that none of the 3D printed syntactic foam core sandwiches fractured due to shear failure.