RESUMEN
Fiber-reinforced thermoplastic composites (FRTPs) are gaining increasing attention and widespread use in engineering applications due to their high specific strength and stiffness, excellent toughness, and recyclability. The mechanical properties of these composites are closely tied to their crystallization process, making it crucial to accurately describe this phenomenon. Existing theoretical models for analyzing the non-isothermal crystallization of thermoplastic composites often face challenges relating to the complexity of obtaining multiple parameters and the difficulty of achieving a final relative crystallinity of 1. To address these issues, this paper introduces a novel functional form of the crystallization rate parameter K(T), tailored for engineering applications, and proposes an improved Mampel model. This model assumes K(T) to be zero before the onset of crystallization and also to be linearly dependent on temperature thereafter, ensuring that the final relative crystallinity reaches 1. The model requires only two easily accessible parameters: the initial crystallization temperature (Ts) and the linear slope (k). The simplicity of the model makes it particularly well suited to engineering applications. This provides a straightforward and effective tool for describing the non-isothermal crystallization kinetics of fiber-reinforced thermoplastic composites.
RESUMEN
An innovative optimal design framework is developed aiming at enhancing the crashworthiness while ensuring the lightweight design of a hybrid two-dimensional triaxial braided composite (2DTBC) tube, drawing insights from the mesostructure of the composite material. To achieve these goals, we first compile the essential mechanical properties of the 2DTBC using a concentric cylinder model (CCM) and an analytical laminate model. Subsequently, a kriging surrogate model to elucidate the intricate relationship between design variables and macroscopic crashworthiness is developed and validated. Finally, employing multi-objective evolutionary optimization, we identify Pareto optimal solutions, highlighting that reducing the total fiber volume and increasing the glass fiber content in the total fiber volume are crucial for optimal crashworthiness and the lightweight design of the hybrid 2DTBC tube. By integrating advanced predictive modeling techniques with multi-objective evolutionary optimization, the proposed approach not only sheds light on the fundamental principles governing the crashworthiness of hybrid 2DTBC but also provides valuable insights for the design of robust and lightweight composite structures.
RESUMEN
Graphene films (GFs) are promising ultrathin thermally conductive materials for portable electronic devices because of their excellent thermally conductive property, light weight, high flexibility, and low cost. However, the application of GFs is limited due to their poor mechanical properties and through-plane thermal conductivity. Here, a graphene-(graphitized polydopamine)-(carbon nanotube) (G-gPDA-CNT) all-carbon ternary composite film was fabricated by chemical reduction, carbonization, graphitization, and mechanical compaction of the evaporation-assembled (graphene oxide)-PDA@CNT film. The G-gPDA-CNT film exhibited a uniform all-carbon composite structure in which the components of the graphene, gPDA layers, and CNTs were cross-linked by strong covalent bonds. This unique structure promoted the load transfer and energy dissipation between the components by which the mechanical properties of the G-gPDA-CNT film were substantially improved. Furthermore, electron and phonon transfers were also promoted, greatly improving the electrical and thermal conductivities, especially the through-plane thermal conductivity of the G-gPDA-CNT film. The G-gPDA-CNT film showed a tensile strength of 67.5 MPa, 15.1% ultimate tensile strain, toughness of 6.07 MJ/m3, electrical conductivity of 6.7 × 105 S·m-1, in-plane thermal conductivity of 1597 W·m-1·K-1, and through-plane thermal conductivity of 2.65 W·m-1·K-1, which were 2.24, 1.44, 3.16, 1.46, 1.15, and 3.90 times that of the pure GFs, respectively.
