Multimaterial Extrusion-Based Additive Manufacturing of Compliant Crack Arrester: Influence of Interlayer Length, Thickness, and Applied Strain Rate

Additive manufacturing is a useful tool for fabricating complex multimaterial structures. Compliant interlayers (ILs) can easily be introduced into stiff materials to increase toughness and stop or impede crack growth, as is done in nature. The aim herein is to analyze the influence of varying IL lengths and thicknesses on crack propagation in 3D-printed polymers at different loading rates. A glycol-modified poly(ethylene terephthalate) is used as a matrix material, while a thermoplastic elastomer on a copolyester basis serves as an compliant IL. Specimen fabrication is done with a fused filament fabrication 3D printer equipped with a multimaterial unit, which allows to print a component composed of several materials within one print. Additively manufactured Charpy samples are tested in three-point bending at loading rates between 0.1 mm min−1 and 3.8 m s−1. The thickness of the IL almost shows no effect on energy absorption as long as remaining in the same printing orientation and loading rate. For varying IL lengths, a constant fight between crack penetration and crack deflection occurs. At low loading rates, the IL acts as a defect. As the loading rate increases, the total absorbed energy of composites increases compared with the pure matrix material.