Evaluation of the head protection effectiveness of cyclist helmets using full-scale computational biomechanics modelling of cycling accidents

Xiang

Polymers for Advanced Techs

et al. 2022

This paper investigated the effects of printing directions (path of nozzle movement) and strain rates on the performances of short carbon and glass fibers filled polyamide-based composites prepared by fused deposition modeling (FDM). Cylindrical specimens printed in three different printing directions were compressed at a wide range of strain rate. The results showed that, for short fiber reinforced polyamide, the compressive properties of cylindrical specimens were affected by printing directions closely associated with the fiber orientation. The highest elastic modulus and yield strength of short fiber reinforced specimens were obtained when the printing direction was parallel to the applied loading direction, because the orientation of short fibers was preferred to the printing direction. However, at large deformation, the orientation of fibers in specimens changed, accompanied by a decrease in stress. With increasing strain rates, the short fiber reinforced polyamide with different fiber orientations showed different failure modes. However, the compressive behaviors of pure polyamide were similar, although they were printed in different printing directions.

Section: Resultsmentioning

confidence: 99%

Section: Mechanical Properties Of Printed Compositesmentioning

confidence: 99%

Effects of printing direction on quasi‐static and dynamic compressive behavior of 3D printed short fiber reinforced polyamide‐based composites

Xiang

Polymers for Advanced Techs

et al. 2022

“…For example, the question of whether a driver has mental fatigue should be identified. In addition, the impact of the same warning function and different warning methods on driving safety and economy of vehicle should also be focused on in the future, as in [ 54 , 55 ].…”

Section: Discussionmentioning

confidence: 99%

The Real-World Effects of Route Familiarity on Drivers’ Eye Fixations at Urban Intersections in Changsha, China

Guo

Huang

et al. 2022

IJERPH

Self Cite

A crucial factor, route familiarity, can affect traffic safety. Nevertheless, focus on the influence of route familiarity on drivers’ eye fixations at urban intersections has received less attention. Identifying the real-world effect of route familiarity on drivers’ eye fixations at urban intersections in Changsha, China, was the objective of this study. Their visual fixation indicators were recorded while unfamiliar drivers and familiar drivers drove a 9 km-long route with nine intersections in an urban environment, but their effectiveness was indicated by the data collected 150 m before the lane stop and 50 m after the lane stop at these intersections. From the analysis of the extracted data, the results indicated that route familiarity could influence drivers’ processing times in the left window (LW) and other areas (OT). Compared with familiar drivers, unfamiliar drivers had longer processing times and higher mental workloads for the right front (RF). For the vehicle’s front (RF, FL, FR), the sampling rates and mental workloads of unfamiliar drivers were higher than those of familiar drivers, but it was the opposite for the driver’s sides (LW, RW) and rear (LM, RM, ReM). It was also indicated that the phenomenon said to increase familiarity with the route and make drivers more likely to be distracted in urban intersections had not been found. From the present findings, the effect of route familiarity on drivers’ eye fixations at urban intersections was confirmed. The high accident risk of familiar drivers could be partly explained by the decrement in drivers’ eye fixation strategies. However, the strategies could not account for the phenomenon that more familiar drivers are involved in rear-end accidents. Therefore, the reason can be investigated based on drivers’ visual scanning strategies, their physiological signals and driving behavior in the future.

“…Hence, the addition of a single type fiber in composites tended to improve some mechanical properties but reduced other mechanical properties at the same time. 19 For structural applications, [20][21][22] considering the balance of mechanical properties, two or more different fibers can be combined to overcome the limitation caused by the presence of single fiber, to have the comprehensive performance improvement and designable properties of composite materials. For example, hybridization of high stiffness carbon fibers with ductile Kevlar fibers combined with a ductile matrix could make composites with good mechanical properties and excellent impact resistance.…”

Section: Introductionmentioning

confidence: 99%

Investigations of quasi‐static indentation properties of 3D printed polyamide/continuous Kevlar/continuous carbon fiber composites

J of Applied Polymer Sci

Zhu

et al. 2022

3D printing technologies are widely used in aerospace, automobile, and other fields due to their rapid manufacture of strong and lightweight products without additional molds and components. However, the relatively low mechanical behaviors of 3D printed composites were due to the weak pristine matrix and the inherent porosity of the fused deposition modeling (FDM) technology. This drawback was compensated by the addition of hybrid continuous fibers for improving the comprehensive and designable characteristics. In addition, the properties of the hybrid composites could be influenced by changing the processing parameters. Therefore, this work aims to study the mechanical properties of designed 3D printed hybrid continuous carbon and Kevlar fibers reinforced polyamide (PA)‐based composites with different fiber layer locations and stacking sequences. The quasi‐static indentation (QSI) tests were conducted to evaluate the mechanical behaviors of the printed composites. The deformation and failure mechanisms of the printed composites were revealed by fractography. Results demonstrated that the printed composites with the middle fiber layer locations showed the highest force value (Fmax) and higher energy absorption capabilities than the printed composites with the fiber layers placed in other locations, which was attributed to the delayed cracking propagation and large delamination, respectively.