This paper presents a combined experimental and numerical study on the low-velocity impact behavior of honeycomb-core sandwich panels with different structural parameters, including facesheet thickness, core height, honeycomb cell size, and cell wall thickness. Impact tests were conducted at four different energies using a drop-weight impact facility, and the deformation and damage characteristics of the tested sandwich panels were analyzed by microscopic X-ray computed tomography. The experimental results revealed two distinct failure modes of sandwich panels: namely mode A, with localized damage in both facesheets and core, which is dominated by indentation; and mode B, which is characterized by global bending deflection of the facesheets and overall core crushing. It was found that a sandwich panel with thin facesheets and a high-density honeycomb core (e.g. with a small cell size and/or a thick cell wall) tended to fail in mode A, but core height did not influence the failure mechanism notably. Furthermore, finite element modeling was carried out to gain further understanding of the effects of these structural parameters. The perforation resistance and energy absorption capacity were significantly enhanced with increasing facesheet thickness. Whereas reducing the cell size and/or thickening the cell wall resulted in lower perforation resistance. When the total thickness of facesheets remained a constant, the impact behavior of the sandwich structure could be optimized by controlling the thickness ratio of the front to back facesheets. Finally, cost efficiency analysis was performed to achieve a rational design of the sandwich structure considering both the impact performance and cost.

On the structural parameters of honeycomb-core sandwich panels against low-velocity impact

The current paper is intended to provide an overview on the current state of the art for sandwich structures marine applications to support their wider application and identify the key issues to de...

Lightweight sandwich structures for marine applications: a review

Mechanical properties and energy absorption capabilities of aluminium foam sandwich structure subjected to low-velocity impact

Design optimization of bioinspired helicoidal CFRPP/GFRPP hybrid composites for multiple low-velocity impact loads

Bio-inspired thin-walled structures have gained growing interests attributed to their excellent performance of energy absorption and lightweight. This study proposes a novel energy absorber by mimicking the structural characteristics of animal long bone, namely bio-inspired multi-cell tube (BIMCT), which comprises laterally-graded multi-cell configuration and the axially-graded aluminum foam. The BIMCTs were respectively fabricated with steel and aluminum for quasi-static crushing tests to explore the corresponding deformation mechanisms, force-displacement curves and interactive effects between tube wall and foam filler. The experimental tests indicated that the steel BIMCT generated a more stable and more regular deformation mode, presenting noticeably higher specific energy absorption (SEA). Furthermore, a numerical modeling study was conducted on the steel BIMCT to analyze the energy absorption mechanism, effects of thickness gradient kt, foam density gradient ktf and average density ρ‾avg of foam on the force-displacement curves, energy absorption (EA), peak crush force (PCF), SEA and the interactive effects between the tube wall and graded metallic foam. Finally, a theoretical model was developed based upon the so-called simplified super folding element method to predict the mean crushing force of BIMCT analytically. The comparative analysis results indicated that the proposed theoretical model is applicable of both the BIMCT and its empty counterpart. This study is anticipated to demonstrate a new way for developing a superior bio-inspired structure for energy absorption. 

A bio-inspired foam-filled multi-cell structural configuration for energy absorption

On low-velocity impact response of foam-core sandwich panels

Effects of radiation reabsorption on the laminar flame speed and NO emission during aviation kerosene combustion at elevated pressures

Insufficient equalization of public services and coexistence of high investment and low consumption are two major dilemmas facing the high-quality development of China’s economy. This study first evaluated the level of equalization of public services by provincial panel data from 2013 to 2017. Then econometric models were constructed to investigate the effect of the equalization of public services on the regional disparities in the ratio of investment to consumption (IC). Results show that the overall level of equalization of public services in China is low and there are large regional differences. Average values of the relative level of equalization of public services show an increasing trend in order of the eastern, central, northeastern, and western regions. The ratio of IC in China also exhibits large regional differences. Public education significantly negatively affects the IC in China, and the effects exist in the eastern and central regions. The seven evaluation criteria of equalization of public services in different regions have different effects on the ratio of investment to consumption. Therefore, according to the characteristics of the relationship between the equalization of public services and the ratio of investment to consumption at the whole or regional scales, a reasonable pathway should be selected to improve the current situation of high investment and low consumption and promote high-quality and sustainable development of the Chinese economy under the new normal.

https://journals.sagepub.com/doi/pdf/10.1177/21582440221085007

Does the Equalization of Public Services Effect Regional Disparities in the Ratio of Investment to Consumption? Evidence From Provincial Level in China

In the traditional non-invasive load monitoring (NILM) algorithms, the identification accuracy is enhanced with the increased network scale while sacrificing the calculation speed, which restricts the efficiency of the load identification. In this study, a multi-feature (active/reactive power and current peak-to-peak value) fusion algorithm is proposed, which can achieve enhanced identification accuracy with a smaller network scale while maintaining the calculation speed. The features of the power and current amplitudes of the loads are transformed into the values of red-green-blue (RGB) color channels by color coding and then fused into the V-I trajectory features. After that, the true-color feature image with higher discrimination is generated and input into the convolutional neural network (CNN). The testing results on the PLAID data set indicate that in comparison with the traditional load identification algorithm, the algorithm proposed in this study performs higher identification accuracy with a smaller neural network parameter scale, which significantly improves the identification efficiency.

/pdf/non-invasive-load-identification-algorithm-based-on-color-u5dul3d1.pdf

Non-Invasive Load Identification Algorithm Based on Color Coding and Feature Fusion of Power and Current

The management of water environments is an important public policy issue. With accelerated industrialization, China’s water quality has deteriorated to one of the lowest levels in the world. Against this background, analyzing the spatial agglomeration characteristics and driving mechanisms of water pollution-intensive enterprises (WPIEs) can help local governments formulate regulations to better manage pollution by enterprises. This study used nearest-neighbor index analysis, global spatial autocorrelation analysis, hot spot analysis, and spatial regression to investigate spatial distribution changes in WPIEs. Further, a spatial autoregressive (SAR) model was used to examine the effects of enterprise agglomeration and environmental regulation on changes in the quantity of WPIEs in the Yangtze River Economic Belt (YREB) from 1998 to 2012. The results showed that the overall quantity of WPIEs in the YREB grew significantly, though growth in the downstream regions gradually slowed from 2005 to 2012. The distribution of WPIEs showed obvious spatial agglomeration characteristics, gradually expanding from a single-core pattern to a multicore one. Enterprise agglomeration and environmental regulation had scale effects on the spatial distribution of WPIEs, yet the effect of environmental regulation was not significant. However, other factors influencing the spatial distribution of WPIEs are complex, and the influence of the boundary effect was found to be more significant.

Spatiotemporal Variations of Water Pollution-Intensive Enterprises and Influencing Factors in China’s “Two Control Zone” Policy Using Spatial Statistics and Spatial Autoregressive Models

Hao Liu

Papers

On low-velocity impact response of foam-core sandwich panels

Effects of radiation reabsorption on the laminar flame speed and NO emission during aviation kerosene combustion at elevated pressures

Does the Equalization of Public Services Effect Regional Disparities in the Ratio of Investment to Consumption? Evidence From Provincial Level in China

Non-Invasive Load Identification Algorithm Based on Color Coding and Feature Fusion of Power and Current

Spatiotemporal Variations of Water Pollution-Intensive Enterprises and Influencing Factors in China’s “Two Control Zone” Policy Using Spatial Statistics and Spatial Autoregressive Models