Creating Stronger Interfaces in Additively Manufactured Multimaterial Polymer Composites Under Shear Loading

Abstract

Abstract This study proposes a bio-inspired approach to enhance the shear strength of interfaces in multi-material composites that are created using additive manufacturing. The Fused Filament fabrication (FFF) technique is used to control the interface morphology and to establish a seamless connection between the hard (Polylactic Acid - PLA) and soft (Thermoplastic Polyurethane - TPU) materials via suture morphology. The study investigates the relationship between the protrusion length of the sutural structures and the overlap distance (i.e., FFF parameter) by conducting microscopic examinations. The interlaminar shear strength of the multi-material composites is tested using the short beam shear test, and the Digital Image Correlation (DIC) technique is used to monitor the interlaminar damage nucleation and evolution. The results demonstrate that the flexural stiffness of the soft-hard polymer composites is significantly affected by the interfacial morphology, with longer protrusion lengths leading to increased stiffness. Stiffness of the structure increased three times by proposed method. Furthermore, the interlaminar shear strength is found to increase with protrusion length, while the onset of non-linear deformation is postponed. Stress values which non linear deformation stats and stress values which crack initiates enhanced by five-six times with increased protrusion length. The main finding of this study is that longer protrusion lengths promote more effective and uniform stress distribution at the interfaces, resulting in a transition from heterogeneous to homogeneous material behavior.