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This thesis presents an integrated modeling‐and‐experimental study aimed at predicting and optimizing the mechanical performance of Fused Deposition Modeling (FDM)–printed polymer parts. While FDM enables rapid, low-waste fabrication of complex geometries, the pronounced anisotropy and nonlinearity inherent to layer-by-layer deposition pose significant challenges for reliable design.
First, a suite of hyperelastic constitutive laws, such as, Neo-Hookean, two and three parameter Mooney–Rivlin, third-order Yeoh, and Gent—was reviewed and formulated in tensorial form for PLA+. Through curve fitting with regression analysis and Finite Element Analysis (FEA) in ANSYS Mechanical, all the models were validated. These model captures non-linear response with large-strain accuracy for PLA+ and established a best practiced model for large-strain uniaxial tension.
Second, the selected models were calibrated against a comprehensive experimental matrix of ASTM D638 Type IV specimens printed at four infill densities (20 %, 50 %, 80 %, 100 %) and four raster angles (0°/90°, 30°/–60°, ±45°, 75°/–15°) for ABS. Nonlinear leastsquares fitting of simulated stress–strain curves to tensile data (n = 4 per condition) yielded average goodness-of-fit values of R² = 0.986 for three-parameter Mooney–Rivlin and thirdorder Yeoh models, outperforming simpler laws by >7 %. However, Neo-Hookean model was chosen for its single variable equation, and a third order polynomial equation captures the materials constant C10 perfectly with R2=1.
Third, static tensile and tension–tension fatigue tests quantified the influence of infill and raster orientation on ultimate tensile strength, yield strength, young’s modulus, elongation, and fatigue life (3 times increase when fibers are cross aligned and higher frequency). Statistical analysis, such as, regression, ANOVA, Post-hoc HSD and Power law analysis (Only for fatigue) revealed higher fill levels gave stronger parts and much longer fatigue life.
Together, these results validate a predictive framework that links process parameters, constitutive model selection, and experimental calibration, enabling informed design of FDM parts for structural applications. The methodology can be extended to viscoelastic damage laws, multi-material prints, and service-condition validation, thereby advancing FDM from prototyping toward reliable end-use manufacturing.
