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The development of impact-resistant composite materials for protective applications such as helmet and body armor has attracted considerable attention. In this study, a novel aramid fiber-woven thermoplastic-epoxy composite was developed. Furthermore, three types of woven textiles, namely three-dimensional (3D) orthogonal-woven (3DOW), 3D angle-interlock woven (3DAIW), and two-dimensional plain-woven (2DPW) textiles, were used as reinforcement structures. To study the effect of the woven structure, impact energy, and damage repairment on impact-resistance performance of these composites, low-velocity drop-weight impact tests with various impact scenarios, such as single-impact, repeated-impact, as well as multiple-impact with hot-press damage repairment, were conducted. The results revealed that the woven structure exhibited an obvious effect on the composite impact-resistance performance and failure modes when subjected to specific impact scenarios. For the single-impact scenario, especially under high impact energy levels (10 and 20 J), the 3DOW structure exhibited superior impact-resistance performance as well as damage tolerance, followed by 3DAIW and 2DPW structures. Furthermore, 3DOW achieved superior impact-resistance to the other two structures for the 10-J repeated-impact scenario. The 3DAIW structure, in which debonding or delamination as well as severe resin cracks dominated, achieved superior impact-resistance to multiple impacts with damage repairment. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) have attracted considerable attention as nanomechanical resonators because of their exceptional mechanical properties and nanoscale dimensions. In this study, a novel CNT-based probe is proposed as an efficient nanoforce sensing nanomaterial that detects external pressure. The CNT probe was designed to be fixed by clamping tunable outer CNTs. By using the mobile-supported outer CNT, the position of the partially clamped outer CNT can be controllably shifted, effectively tuning its resonant frequency. This study comprehensively investigates the modeling and vibration analysis of gigahertz frequencies with loaded CNTs used in sensing applications. The vibration frequency of a partially clamped CNT probe under axial loading was modeled using continuum mechanics, considering various parameters such as the clamping location, length, and boundary conditions. In addition, the interaction between external forces and CNT resonators was investigated to evaluate their sensitivity for force sensing. Our results provide valuable insights into the design and optimization of CNT-based nanomechanical resonators for high-performance force sensing applications. [ABSTRACT FROM AUTHOR]

Resin pre-coating technology is widely used in all aspects of composite materials, especially in the repair of composite materials. The pre-coating is formed by combining acetone with the resin, which is diffused and cured by the epoxy adhesive at the same time. It acts as an interlock to prevent the interface from debonding and to fill in the damaged cracks. The capillary action of acetone allows the resin to permeate the cracks in the fiber damage layers, thus filling the cracks and completing the repair. The pre-coating solutions of 10 wt%, 20 wt%, 25 wt%, 35 wt%, and 45 wt% resin were applied to damaged areas respectively, and cured at 60°C for 7 days. The crack filling effect was observed by scanning electronic microscopy (SEM). At the same concentration, the effect of prolonged repair time was also studied. The other two repair times were 14 days and 30 days respectively. In addition, the tensile properties of the materials before and after repair were tested and compared. The results showed that 25 wt% resin pre-coating had the best repair performance after 7 days, with a repair rate of 27%, which was 22% higher than the conventional repair without resin pre-coating. However, the repair effect became more obvious after the extension of repair time, and the repair effect of 25 wt% resin pre-coating reached 44% after 30 days curing. Therefore, it was found that the resin can fully penetrate the cracks in the damaged area with resin pre-coating technology, and 25 wt% resin pre-coating solution is the best choice. [ABSTRACT FROM AUTHOR]