Gen Li

Damage detection and localization in carbon fiber composites using electrical resistance tomography (ERT) face significant challenges related to imaging algorithms and hyperparameter optimization. This study introduces a novel framework that combines hybrid regularization with Bayesian optimization to achieve precise damage localization in three‐dimensional (3D) woven composites. The Bayesian optimization process autonomously identifies the optimal hyperparameters for the hybrid regularization algorithms, enhancing the quality of the resulting damage images. We evaluated the performance of a hybrid of L1 and Iteratively Reweighted L2 (L1‐IRL2) regularization algorithms. The findings indicate that the algorithm produces superior reconstruction quality when compared to traditional methods. Furthermore, it successfully locates damages in the less sensitive central region, an area where the traditional algorithms struggled. The proposed approach demonstrated improved robustness to noise; even with a signal‐to‐noise ratio of 20 dB, it maintained a clear background image while accurately identifying damage areas. This investigation validates the effectiveness of the proposed Bayesian optimization hybrid regularization framework for damage localization in complex 3D woven composites.

The variations in electrical resistance of carbon fiber composites under different damage modes are critical for the design of electrically conductive components. Here, we developed a fiber random contact model to analyze the changes in electrical resistance of carbon fiber composites subjected to various damage scenarios. An ideal rectangular grid was constructed in matrix form utilizing the nodal voltage and current method. The electrical resistance of each fiber branch was calculated based on the normal distribution of fiber orientation angles. To simulate the random distribution of contact branches among fiber contact points within the resistor network, contact branches were randomly removed from the ideal rectangular grid. The electric conductive properties of carbon fiber tows, unidirectional carbon fiber composites, and 3D woven carbon fiber composites were measured to validate the fiber random contact model. The findings are anticipated to contribute to the optimization of carbon fiber composites for electrical applications.Highlights: Fiber random lap model for evaluating electrical behavior was developed. The conductive behaviors of the composites were measured. Electrical resistance variation under various damages was investigated.

Investigating the macro‐mechanical properties of polymer composites at the nanoscale is a challenging topic. Here we report the compressive performances of carbon fiber‐reinforced epoxy composites using molecular dynamics (MD) simulations. The evolution of microstructure and microscopic energy, including free volume, radius of gyration, dihedral angle, potential energy, and interaction energy, has been investigated to characterize compressive behaviors at the nanoscale. Molecular chains gradually bend, and the movement space of the molecular chains decreases during compression loading. The radius of gyration and dihedral angle are deformed into a state of irreversible plasticity to accommodate the microstructural transformation. The interaction energy increases and subsequently declines as the carbon fiber/epoxy interface gets closer, reflecting the transition of the internal structure. The inhomogeneity and interfacial concentration distribution of stress, and local molecular stiffness under various strains have been obtained to reveal the nanoscopic mechanism of epoxy failure and interface delamination during compression. This study reveals the compression behaviors and deformation mechanism of carbon fiber‐reinforced epoxy composites at the molecular level, providing directions and possibilities for molecular design and structural optimization of composites.Highlights: The nanoscopic compression deformation of CFRP composites is studied. Microstructural evolution and conformation transformation are revealed. The evolution and transition of microscopic energy are analyzed. Micro‐mechanism of epoxy deformation and interface delamination is elucidated.