Fused deposition modeling (FDM), a material extrusion additive manufacturing process, has emerged as a method of choice for the fabrication of polymeric tissue engineering scaffolds. The FDM process is intrinsically complex, consisting of a multitude of parameters; in addition, there are material-machine-process interactions, which inevitably influence the mechanical properties, the surface morphology, and ultimately the functional integrity of fabricated bone structures. Consequently, physics-based process characterization and optimization in the FDM process is a burgeoning need. The overarching goal of this research work is to fabricate patient-specific, biocompatible, and biodegradable bone scaffolds for the treatment of osseous defects, fractures, and diseases. In pursuit of this goal, the objectives are to: (i) investigate the influence of consequential parameters of FDM on the functional properties of fabricated femur bone structures; and (ii) investigate the underlying physical phenomena behind the experimental observations using a computational finite-element model.

In this study, biocompatible femur bone structures were FDM-deposited, based on a medical-grade polymer composite, composed of polyamide, polyolefin, and cellulose fibers. A new test specimen was designed, based on an X-ray micro-CT scan of a femur bone as well as the ASTM D638-14 (Type II) standard. In addition, the experimental characterization was on the basis of a cascade approach, composed of the following experimental deigns: (i) fractional-factorial design, utilized for factor screening and identification of consequential process parameters; (ii) Taguchi design, utilized for process optimization. Besides, a computational finite-element model was forwarded to investigate the underlying physical phenomena behind the experimental observations.

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