今日更新：Composites Part A: Applied Science and Manufacturing 1 篇，Composites Part B: Engineering 2 篇，Composites Science and Technology 1 篇
Composites Part A: Applied Science and Manufacturing
High toughness, flexible and thermally conductive fluorine rubber composite films reinforced by hexagonal boron nitride flakes for thermal management
Jing Chen, Yibing Lin, Wanbiao Hu, Yuanlie Yu
doi:10.1016/j.compositesa.2024.108466
热管理用六方氮化硼片增强的高韧性、柔性和导热氟橡胶复合薄膜
The rapid advancement of electronic information technology has generated a substantial demand for polymer-based thermal management materials. In order to address the challenges of heat dissipation and avoid signal interference, it is essential to develop polymer-based thermal management materials with both high thermal conductivity and low dielectric properties. Herein, hexagonal boron nitride flakes (h-BNFs) with a high aspect ratio and some hydroxyl groups were prepared using the high pressure homogenization technique. Subsequently, h-BNF/fluorine rubber (h-BNF/FKM) composite films were fabricated through a simple and scalable blade coating method. During the blade coating process, most of the h-BNFs can align with their (002) crystal planes paralleling to the horizontal direction. In addition, the rest of the h-BNFs will randomly distribute and overlap with each other, combining with the horizontally aligned h-BNFs to form a distinctive three-dimensional packing network. This unique network structure enables the h-BNF/FKM composite films to have thermal conductivities of up to 0.44 W/(m·K). Moreover, the introduction of h-BNFs can effectively reduce the dielectric constants and dielectric losses of FKM films. More importantly, the h-BNF/FKM composite films also exhibit outstanding mechanical toughness, excellent flexibility, good adhesion and improved flame-retardancy, providing promising applications in the electronic device thermal management.
This study proposed an innovative method for enhancing the interlaminar fracture resistance of carbon fibre/epoxy composites by incorporating structured low-melt polyaryletherketone meshes (LMPAEK) meshes. LMPAEK films were machined into structured hollow meshes and then surface-treated using high-power UV-irradiation. These treatments significantly increased the contact area and interface adhesion between the LMPAEK inserts and the composite matrix, leading to substantial improvement in the interlaminar fracture performance of the composite. Fracture test results demonstrated that the mode-I and mode-II fracture propagation energies of the LMPAEK-inserted composite at 22 °C were 1.04 times and 13.92 times higher, respectively, than those of the reference composite. Similarly, at 130 °C, their mode-I and mode-II fracture propagation energies were 1.36 times and 8.56 times higher, respectively. The remarkable fracture performance of the LMPAEK-inserted composites were attributed to the substantial plastic deformation and damage of the LMPAEK resins, which possessed exceptional mechanical properties and thermal resistance.
The inherent weakness and variability in the interlaminar properties of composites and associated delamination pose significant challenges, compromising the performance of composite structures. This study investigates a strategy to tailor the apparent interlaminar resistance by altering the geometry of the interface to control crack propagation. We have developed analytical models, which propose a formulation that links the geometry, i.e. the interface width change rate and shape factor of the crack growth plane, with the reaction force–displacement curve. The results obtained, a family of power law relations followed during interlaminar crack growth, indicate that the analytical formulation is valid for all geometries tested, including those with significant width change rates; however, it may not always be easy to use or interpret. An approximated solution, constrained to slowly varying geometries, is also proposed. The limits of using this model are presented and discussed. The final validation of the models is performed using numerical and experimental approaches, considering the delamination of carbon fibre laminates. This work offers new insights into the design of composites and the fracture process in general, featuring unique shapes and improved crack resistance. It also addresses practical issues, e.g., related to composite repairs, which can enhance the performance and longevity of composite structures. Specifically, the proposed formulations can be easily adopted to obtain optimized patch geometries.
The shape memory cyclic behavior and mechanical durability of the shape memory polymer (SMP) and three woven fabrics (plain, twill, and satin weaves) reinforced shape memory polymer composite (WFR-SMPCs) are characterized to investigate the effect of woven textures on the mechanical and shape memory properties of WFR-SMPCs. Shape memory cycle test, shape memory durability test, and microscopic observation for SMP and WFR-SMPCs were carried out. Experimental results show that the SMP is temperature-sensitive, and higher temperature facilitates the shape memory performance of the material. The woven fabric reinforcements can significantly enhance the mechanical properties of the SMP matrix while still maintaining good shape recovery ratios above 98% and shape fixation ratios above 90% even though there is a slight decrease in these values. The twill WFR-SMPC displays the best mechanical performance. The satin WFR-SMPC has the highest shape recovery ratio. The twill WFR-SMPC performs the best in load-bearing capacity and recovery stress. The microscopic observations show that the rotational misalignment and bending of the fiber tows, and damage to the matrix are the main failure modes of the WFR-SMPCs at high shear strain.
