The most attractive structural feature of the three-dimensional (3D) angle-interlock woven structure is that the straight weft yarns are bundled by the undulated warp yarns, which induces the overall good structural stability and a stable fabric structure. Thus the 3-D angle-interlock woven composite (3DAWC) prepared by the vacuum-assisted resin transfer molding (VARTM) curing process has excellent mechanical properties by using the fabric and epoxy resin as the reinforcement and matrix, respectively. The low-velocity impact damage properties of the composites under different drop-weight energies (70, 80, and 100 J) were tested experimentally. The load–displacement curves, energy–time curves, and the ultimate failure modes were obtained to analyze the performance of resistance to low-velocity impact, as well as the impact energy absorption effect and failure mechanism, especially the structural damage characteristics of the 3DAWC subjected to the low-velocity impact of drop weight. By analyzing the obtained experimental results, it is found that the fabric reinforcement is the primary energy absorption component and the impact energy mainly propagates along the longitudinal direction of the yarns, especially the weft yarn system, which is arranged in a straight way. In addition, as the impact energy increases, the energy absorbed and dissipated by the composite increases simultaneously. This phenomenon is manifested in the severity of deformation and damage of the material, i.e., the amount of deformation and size of the damaged area.
The quasi-static tensile damage behavior of one type of layer-to-layer 3-Dimensional Angle-interlock Woven Composite (3DAWC) was tested and analyzed in this paper. Incorporated with the acoustic emission (AE) events monitoring, the mechanical behavior of the 3DAWC under tensile loading condition was characterized. The Load-Extension curve, Load/AE events-Time curves occurred during the entire testing process and tensile damage modes were recorded to characterize and summarize the mechanical properties and damage mechanism of the 3DAWC subjected to tensile loading. It was found that the tensile damage of the 3DAWC could be summarized into 3 steps. And each step has a distinct primary damage mode. Moreover, the resin cracks, resin-yarn interface debonding and yarn breakages were the main damage modes for the 3DAWC.
Objective Patients with H1N1 virus infection were hospitalized and quarantined, and some of them developed into acute respiratory failure, and were transfered to the medical intensive care unit of Beijing Ditan Hospital, Capital Medical University in Beijing, China.
Methods The clinical features and preliminary epidemiologic findings among 30 patients with confirmed H1N1 virus infection who developed into acute respiratory failure for ventilatory support were investigated.
Results A total of 30 patients (37.43 ± 18.80 years old) with 2009 influenza A (H1N1) related acute respiratory distress syndrome (ARDS) received treatment with mechanical ventilation, 15 cases of whom were male and 17 cases died of ARDS. Fatal cases were significantly associated with an APACHE Ⅱ score (P = 0.016), but not with PaO2/FIO2 (P = 0.912) and chest radiograph (P = 0.333). The most common complication was acute renal failure (n = 9). Five patients received extracorporeal membrane oxygenation (ECMO), 3 of whom died and the others survived. The major causes of death were multiple organ dysfunction syndrome (MODS) (39%), intractable respiratory failure (27%) and sepsis (20%).
Conclusions Most patients with respiratory failure due to influenza A (H1N1) virus infection were young, with a high mortality, particularly associated with APACHE ∥ score, secondary infection of lung or type 2 diabetes mellitus.
Three-dimensional angle-interlock woven composites (3DAWCs) are widely used for their excellent mechanical properties. The most significant feature is the existence of the undulated warp yarns along the thickness direction, which makes it interesting to study the mechanical properties in the warp direction. The quasi-static tensile behavior of a layer-to-layer 3DAWC along the undulated warp direction was studied by experimental and finite element analysis (FEA) methods. Based on the experimental results, the typical failure mode involving fibers, resin, and their interfaces was found. According to the FEA results, the stress concentration effect, key structural regions, and microstructural (yarn and resin) damage mechanism were obtained, which provided effective guidance for structural optimization design of the 3DAWC with stronger tensile resistance performance. In addition, the three-step progressive failure process of the 3DAWC under quasi-static tensile load was also described at the “yarn–resin” microstructural level.