Numerical Assessment of a Sustainable Blast Protection Wall

Terrorist attacks have increased in the past few years in different countries. Explosions are problem that has significant impact on human life, as well as the social and economic situations. Engineers have designed targeted structures to mitigate blast effects. However, design blast-resistant systems is pricey and not suitable choice in most cases. Therefore, install blast barriers to protect occupants and instructed can reduce casualties and losses. Most current studies have investigated the performance of multi-layer composite blast barriers composed of advanced materials, which is not only costly, but require skilled labour to construct. The present study conducts numerical analysis of eco-friendly composite blast protection wall to mitigate blast. The wall structure consists of two face-sheet of adobe brick and core layer of crushed recycled aggregate. The analysis framework includes three different blast wall models using ABAQUS®. The explosive charge of 1-kilogram TNT is placed at different standoff distances from 0.25 to 4.0 meter in front of the wall. The authors conclude sustainable materials to design blast barriers could be effective in reducing the intensity of explosions in certain blast scenarios. The thickness of the core layer and standoff distance have the main contribution to identify the blast response of the blast wall. For instance, the calculated out-of-plane displacement results showed when 1- kg TNT place at 0.5-m from the wall, and thickness of the core increases from 30-cm to 60-cm, the displacement decreases by 38.74%. While the acceleration decreases by 75% for the same range of increase of thickness of the core layer. The present study calls researchers to investigate the performance of low-cost, and environment-friendly materials to attenuate abnormal loads wether are man-made or natural hazards.

Sacrificial Cladding with Brittle Materials for Blast Protection

In the following work, sacrificial claddings filled with different brittle materials were investigated, from concrete foam to granular media. They were subjected to blast loading using an explosive driven shock tube, while a sensor measures the load transmission and a high speed camera records the compression of the core. From a macroscopic point of view, concrete foam and granular media can act efficiently as a crushable core but differs greatly in terms of energy dissipation mechanisms. To compare them, granular media was at first treated as a cellular material, and different key parameters (plateau stress, densification strain) were computed using the energy absorption efficiency methodology. The presented tests results, coupled with observation in literature, allow a better understanding on the crushing process of a granular media. In particular, granular media tend to work as a core even for low intensity load, contrary to more classical crushable core.

EARTH FILL INCREASES EFFICACY AND LONGEVITY OF λ-CYHALOTHRIN RESIDUAL INSECTCIDE TREATMENT OF HESCO® BLAST WALL GEOTEXTILE

The prevention of vector-borne disease to protect the health and readiness of United States forces in the field continues to be a high priority for the US Department of Defense. Previous studies have demonstrated that the risk of human contact with disease-vector mosquitoes and other biting flies can be reduced by applying an insecticide to perimeters of military materials such as camouflage netting or HESCO blast protection wall geotextile already in place around troops in the field. In this study we investigated whether residual pesticide efficacy will persist in the presence of earth fill that is required for operational use of HESCOs, using a warm temperate field site in north Florida. Results from laboratory bioassays measuring mosquito mortality and field collections of natural mosquito populations indicated superior efficacy and greater longevity of pesticide treated geotextile exposed to soil fill. These findings not only support immediate implementation of this technique in US military field scenarios, but also provide evidence that HESCO technology currently used in natural disaster flood control could be leveraged to protect civilian personnel from emerging floodwater mosquitoes.

A cosmopolitan fungal pathogen of dicots adopts an endophytic lifestyle on cereal crops and protects them from major fungal diseases

Fungal pathogens are seriously threatening food security and natural ecosystems; efficient and environmentally friendly control methods are essential to help safeguard such resources for increasing human populations on a global scale. Here, we find that Sclerotinia sclerotiorum, a widespread pathogen of dicotyledons, can grow endophytically in wheat, rice, barley, maize, and oat, providing protection against Fusarium head blight, stripe rust, and rice blast. Protection is also provided by disabled S. sclerotiorum strains harboring a hypovirulence virus. The disabled strain DT-8 promoted wheat yields by 4–18% in the field and consistently reduced Fusarium disease by 40–60% across multiple field trials. We term the host-dependent trophism of S. sclerotiorum, destructively pathogenic or mutualistically endophytic, as schizotrophism. As a biotroph, S. sclerotiorum modified the expression of wheat genes involved in disease resistance and photosynthesis and increased the level of IAA. Our study shows that a broad-spectrum pathogen of one group of plants may be employed as a biocontrol agent in a different group of plants where they can be utilized as beneficial microorganisms while avoiding the risk of in-field release of pathogens. Our study also raises provocative questions about the potential role of schizotrophic endophytes in natural ecosystems.

Cork Core Sandwich Plates for Blast Protection

A numerical model is developed and validated to analyse the performance of aluminium skin and agglomerated cork core sandwich plates subjected to blast loads. Two numerical approaches are used and thoroughly compared to generate the blast loading: an Arbitrary-Lagrangian–Eulerian approach and the Load Blast Enhanced method. Both of the models are validated by comparing the numerical results with experimental observations. A detailed analysis of the sandwich behaviour is done for both approaches showing small differences regarding the mechanical response of the sandwich structure. The results obtained from the numerical models uncover the specific energy absorption mechanisms happening within the sandwich plate components. A new core topology is proposed, based on these results, which maximises the energy absorption capacity of the plate, keeping the areal density unchanged. A wavy agglomerated cork core is proposed and the effects of different geometrical parameters on the energy absorption are thoroughly analysed and discussed. The proposed optimised plate configuration shows an increase in the total absorbed energy of close to 40% relative to a reference case with the same areal density. The adopted optimisation methodology can be applied to alternative configurations to increase the performance of sandwich structures under blast events.