TESTING OF INTERLAMINAR PROPERTIES AND PROGRESSIVE FAILURE ANALYSIS OF 3D-PRINTED CFRP

The interlaminar bonding behavior of fused filament fabrication (FFF) 3D-printed composites exhibits nonuniform distribution due to the nozzle path, presenting an incomplete central tearing interface during Interlaminar delamination. To enable interlaminar performance testing and failure prediction of 3D-printed carbon fiber-reinforced polymers (CFRP), a Half-Layer Interrupted Printing with Interstitial Replacement (HIPIR) method, which accounts for printing continuity, is proposed to preserve crack propagation patterns consistent with practical conditions in pre-cracked specimens. Based on the designed specimens, interlaminar Mode-I (DCB), Mode-II (ENF), and mixed Mode I-II (MMB, β = 15% ~ 90%) tests are conducted to systematically obtain interlaminar fracture toughness for each mode. Furthermore, a parameter identification framework combining cohesive zone modeling and experimental cross-validation is established to evaluate key mechanical parameters during damage initiation, crack propagation, and local tearing processes. Results show that the designed specimens effectively replicate brittle peeling and local delamination features observed in FFF 3D-printed CFRP failure. Cross-validation between experiments and numerical models allows for the precise identification of a key mechanical parameter system, including interfacial strength, initial stiffness, and fracture toughness. Numerical predictions from the constructed progressive failure model for mixed Mode I-II exhibit relative errors below 15% compared with experimental measurements, demonstrating high accuracy and engineering predictive capability. This research provides a reliable theoretical basis for quantitative evaluation of interlaminar failure and structural design of FFF 3D-printed CFRP.