Fracture mechanics-based investigation of bioinspired soft-hard interfaces fabricated by multi-material additive manufacturing

Date

2024-1-17

Author

Altuntaş, Umut

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This study presents a facile strategy for architecting the interface morphology to create tougher and stronger interfaces in additively manufactured multi-material polymer composites. A sutural interfacial morphology between two dissimilar polymer phases PLA (Polylactic acid-hard material) and TPU (Thermoplastic Polyurethane-soft material) is designed and fabricated by the fused filament fabrication technique. The proposed strategy utilizes one of the process parameters (i.e., overlap distance) to create sutural interfaces with soft protrusions. The microscopic inspections of the interface suggest that the proposed strategy can control the protrusion length, which indirectly influences the interfacial defect density. A positive correlation between the overlap distance and resulting protrusion amplitude is obtained. In the first part of the thesis, the interfacial toughness measurements by the double cantilever beam test reveal a linear correlation between the interfacial toughness and protrusion amplitude. The proposed interfacial architecture can result in up to a 16–18-fold increase in the interfacial toughness in comparison with the baseline interface. In the second part of the thesis, The interfacial cohesive-traction separation curves are experimentally obtained using the digital image correlation method. The fracture mechanics-based interfacial adhesion test method is developed utilizing double-edge notched Tensile geometry to accurately determine the interfacial fracture characteristics. It is shown that as the protrusion length increases, the critical stress increases in addition to the traction-separation curves transitioning from a triangular form to a trapezoidal form. In the third part of the thesis, the interlaminar shear strength of the architected interface is measured using the short beam test method, and the failure process is further examined through digital image correlation measurements. The findings suggest that the interlaminar shear strength and interface stiffness gradually increase as the protrusion length grows.

Subject Keywords

Fracture mechanics, Additive manufacturing, Tougher interfaces, Interface morphology, Experimental solid mechanics

URI

https://hdl.handle.net/11511/108406

Collections

Graduate School of Natural and Applied Sciences, Thesis