Fabrication of a gradient-in-a-gradient structure in functionally graded polymer composites via additive manufacturing

Purpose TFused Filament Fabrication (FFF) is an established additive manufacturing (AM) process for prototyping thermoplastic components, characterized by inexpensive equipment and materials, high usability and accessible process control. Many FFF systems allow the use of two different materials within a single build, although the second material is typically limited to support structures and interlayer adhesion between dissimilar materials is often weak. The purpose of this work is to investigate whether smooth material transitions generated by a nozzle design that combines two feedstock materials into a single bead can improve adhesion and enable Functionally Graded Materials (FGM). Design/methodology/approach In the applied methodology, a modified FFF process referred to as Functionally Graded Additive Manufacturing (FGAM) is used to fabricate components from PLA and TPU with continuously varying material ratios, allowing systematic evaluation of compositional gradients. Findings The findings show that a changing PLA:TPU ratio requires an adjustment of processing temperature to maintain bonding quality, while continuous transitions can enhance interlayer adhesion compared to distinct material changes. The originality of this work lies in extending gradient-based processing to multimaterial thermoplastic AM and proposing a new production mechanism termed “gradient-in-a-gradient.” Practical implications The implications include the possibility of tailoring component composition to pre-defined load profiles while combining bio-based and crude oil-based polymers to support resource-efficient AM production. Originality/value The originality of this work lies in extending gradient-based processing to multimaterial thermoplastic AM and proposing a new production mechanism termed “gradient-in-a-gradient.” The implications include the possibility of tailoring component composition to pre-defined load profiles while combining bio-based and crude oil-based polymers to support resource-efficient AM production.