Uncertainty quantification of load–unload tensile response of continuous fiber additively manufactured composites

Continuous-fiber fused filament fabrication (FFF) enables laminate-like architectures with tunable anisotropy, but structural use requires quantifying consistency in addition to mean response. This study examines the low-strain load–unload tensile response of continuous carbon-fiber/polyamide (CCF-PA) laminate-like architectures using a batch-blocked design that separates layup-dependent behavior from build-to-build and print-bed-location variability. Forty-five specimens were produced across three symmetric stacking sequences, three batches per sequence, and five fixed bed locations per batch, and were tested in a single load–unload cycle to 1 kN. Stress-window tangent moduli, permanent set, and dissipated energy density were extracted from the measured response. Across sequences, unloading tangent moduli generally exceeded loading tangent moduli, particularly in the mid- and high-stress windows, showing a repeatable path-dependent asymmetry under the present low-strain protocol. Importantly, the layup with the largest hysteresis did not show the largest modulus scatter; instead, the ±45^∘ architecture showed the tightest modulus distributions, whereas layups containing 0^∘/90^∘ plies exhibited broader scatter. Per-sequence variance partitioning further showed that the relative contributions of batch and fixed location effects depend on layup and response metric, with build-to-build effects generally more influential. Qualitative micro-CT observations, including a high-resolution scan of a continuous-fiber turn region, further indicated that local steering features can contain pronounced voids and geometric irregularities not captured by average porosity alone. These results establish architecture-specific baselines for qualification and process monitoring of continuous-fiber FFF composites and provide experimentally grounded guidance for constitutive modeling of printed composites with nonlinear, history-dependent low-strain response.