Composites Science and Technology最新文献

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.

Flexible electronic devices require stretchable packaging materials that provide a hermetic seal. However, conventional soft materials often exhibit strong gas permeability, making it difficult to achieve stable operation, which requires films with high deformability, self-healing capability, and gas barrier functionality. In this study, a layer by layer (LBL) method was employed to uniformly coat a controllable thickness of liquid metal (LM) onto a designed and synthesized self-healing thermoplastic polyurethane (TPU) film, successfully developing a stretchable gas barrier film (TPU/LM) with high gas barrier properties. The designed polyurethane film significantly enhanced the adhesion of the liquid metal, effectively preventing leakage. The experimental results show that the water vapor transmission rate (WVTR) of the TPU/LM composite film with a thickness of 40 μm is 4.04g/(m²·day). Compared to the film without LM, the gas barrier performance has been improved by approximately 16 times. Additionally, there is a significant enhancement in nitrogen (N₂) barrier, with a permeation rate reaching 4.0*10⁻¹⁷ cm³ cm/(cm²·s·Pa), effectively blocking the N₂ permeation. This demonstrates the universality of the TPU/LM in gas barrier applications. Furthermore, the TPU/LM film also demonstrated excellent electromagnetic shielding effectiveness. The self-healing capability of the stretchable gas barrier film allows it to recover its initial gas barrier performance after mechanical damage. Humidity-sensitive resistors encapsulated with TPU/LM exhibited stable operation in both air and 90 % humidity environments, confirming the superior barrier properties of the TPU/LM. Generally, the developed TPU/LM is suitable for packaging applications in the next generation of flexible electronic devices.

Lightweight tubular composite materials with excellent compression performance are important structural components for load-bearing or energy absorption. Generally, outstanding performance depends on the structural design. Herein, a progressive structural optimization of 3D angle-interlock tubular woven reinforced composites (3DATWCs) is performed. The structural factors under consideration involve proportion of warp lining yarn, layers of weft yarn, surface constraint yarn and weft density. The axial compression performance and failure process of 3DATWCs with different structures are investigated through experiments and finite element method. The results indicate that increasing proportion of warp lining yarn can significantly improve the axial compression performance of 3DATWC. However, simply increasing proportion of warp lining yarn may decrease the straightness of yarn and constraint on warp yarns, leading to the performance reduction. The problem of performance reduction can be solved by introducing surface constraint yarn or increasing weft density. Finally, an optimization strategy is unveiled. Compared to ordinary structure, the ultimate load, plateau average load, ultimate stress, elastic modulus, total energy absorption and specific energy absorption of optimized 3DATWC increase by 101.88 %, 96.12 %, 77.46 %, 142.55 %, 119.06 %, and 77.39 %, respectively. Additionally, the axial compression performance is seriously affected by the fiber waviness, yarn waviness and interfacial properties, and can be further improved through reducing the waviness during the preparation of fabric preform.