Effect of interfacial bonding conditions on the bending behavior of hybrid aluminum/thermoplastic composite tubes manufactured via automated fiber placement

Hybrid aluminum/thermoplastic composite tubes manufactured by automated fiber placement (AFP) are promising energy-absorbing members, yet their performance is governed by the aluminum–laminate interface. We study two nominally identical lay-ups that differ only in the first ply at the aluminum surface (CF/PEEK vs. GF/PEEK) and link interfacial quality to the four-point-bending response. Optical microscopy shows that the GF/PEEK first ply produces smaller gaps at the interface. Correspondingly, mechanical tests exhibit higher initial stiffness, higher peak load, and greater energy absorption relative to the CF/PEEK case. A finite-element framework that replicates the test setup varies only the interface condition—no-bond (contact/friction), partial-bond with a zero-thickness cohesive-zone model (CZM), and full-bond—while bracketing failure with two criteria: a conservative maximum-stress trigger and a mode-aware Hashin formulation. The GF/PEEK configuration shows similarity to the defined partial-bond response, the CF/PEEK configuration to the no-bond limit, and the full-bond case defines an achievable upper bound. Overall, the results demonstrate that interfacial condition is an effective lever for improving bending performance in hybrid aluminum/thermoplastic composite tubes.