Blast Response Research Articles

Towards an Understanding of the Effect of Adding a Foam Core on the Blast Performance of Glass Fibre Reinforced Epoxy Laminate Panels.

This paper presents insights into the blast response of sandwich panels with lightweight foam cores and asymmetric (different thicknesses) glass fibre epoxy face sheets. Viscously damped elastic vibrations were observed in the laminates (no core), while the transient response of the sandwich panels was more complex, especially after the peak displacement was observed. The post-peak residual oscillations in the sandwich panels were larger and did not decay as significantly with time when compared to the equivalent mass laminate panel test. Delamination was the predominant mode of failure on the thinner facesheet side of the sandwich panel, whereas cracking and matrix failure were more prominent on the thicker side (which was exposed to the blast). The type of constituent materials used and testing conditions, including the clamping method, influenced the resulting failure modes observed. A probable sequence of damage in the sandwich panels was proposed, based on the transient displacement measurements, a post-test failure analysis, and consideration of the stress wave propagation through the multilayered, multimaterial structure. This work demonstrates the need for detailed understanding of the transient behaviour of multilayered structures with significant elastic energy capacity and a wide range of possible damage mechanisms. The work should prove valuable to structural engineers and designers considering the deployment of foam-core sandwich panels or fibre reinforced polymer laminates in applications when air-blast loading may pose a credible threat.

Finite element modelling of RC slabs retrofitted with CFRP strips under blast loading

This paper presents nonlinear finite element (FE) simulations to predict the structural behavior of simply supported reinforced concrete (RC) slabs retrofitted with carbon fiber reinforced polymer (CFRP) as externally bonded reinforcement (EBR) and subjected to the blast loads in order to evaluate the effectiveness of using the CFRP strips as EBR for blast protection. The objective of this paper is to develop detailed numerical models in order to predict the blast response of non-retrofitted and retrofitted RC slabs during the inbound and rebound phases. A plastic material model including the strain rate effects of the material and able to predict the cracks is used to model the concrete. An elasto-plastic material model and an elastic material model are used to model the steel reinforcement and the CFRP strips, respectively. The bond interface between concrete and CFRP strip is simulated using a special contact algorithm including the strain rate effect at the interface between concrete and CFRP strip with failure criteria. The numerical results are validated by experimental tests. The maximum deflections, crack distribution and strain evolution in the steel reinforcement and in the CFRP strips found by the numerical analysis are in good agreement with the experiments. The concrete material model gives a good prediction of the blast response of the RC slab with and without EBR. Increasing the amount of the CFRP strip reduces the maximum deflection at the mid span of the slabs and the strain distribution in the steel reinforcement and in the CFRP strip. Parametric studies with respect to CFRP width and CFRP thickness are performed in order to evaluate the effects on the blast response of the RC slabs.

Evaluating Complete Remission with Incomplete Hematologic Recovery (CRh) As a Response Criterion in Myelodysplastic Syndromes (MDS)

Evaluating Complete Remission with Incomplete Hematologic Recovery (CRh) As a Response Criterion in Myelodysplastic Syndromes (MDS)

Blast mitigation using polymeric 3D printed auxetic re-entrant honeycomb structures: A preliminary study

Protection of critical infrastructure in an urban environment is a challenging task, specifically against the vehicle bourne improvised explosive device threat. To design infrastructure to withstand this evolving threat, novel solutions and advanced materials need to be developed. One such material of interest are auxetics. This study experimentally analysed the mitigation of blast response of auxetic re-entrant honeycomb structures, with geometries varying between −ve 30° and +ve 30° using additive manufacturing (3D printing) techniques and non-explosive loading via shock tube. Re-entrant auxetic structures (−ve 15°) exhibited repeatable blast mitigation of 23% and reduced the transmitted pressure and impulse of the blast wave. Further highlighting their potential application as a protective measure to enhance a structures blast survivability.

An RHT-Model-Based Equivalent Parameter Scheme for Blast Response Simulation of RC Frames

In this paper, a novel equivalent parameter scheme based on the Riedel–Hiermaier–Thoma (RHT) model is proposed for blast response simulations of reinforced concrete (RC) frames. Considering the strengthening effect of longitudinal and stirrup reinforcements on concretes, constitutive parameters in the RHT model are modified to homogenize RC components based on reasonable simplifications and numerical tests. Numerical results of RC beams illustrate that this scheme significantly improves the computational efficiency and effectively predicts real explosion response behaviors with high accuracy. The scheme is then employed for the blast simulation of an RC frame with multiple components with results compared with those of real frame experiments to further demonstrate its reliability. Owing to its efficiency and accuracy, the present RHT-model-based equivalent parameter scheme can serve as a feasible tool to conduct blast response analysis of the RC frame and guide the corresponding anti-explosion designs.

Mitigating confined blast response of buried steel box structure with foam concrete

The demand and application of buried structures have greatly increased recently. With space partially or fully confined, the safety of buried structures subjected to internal hazards such as explosions is a major concern. In the present study, confined blast mitigation effectiveness of buried steel boxes with foam concrete is experimentally and numerically investigated. Tests with and without foam concrete layer applied to buried steel boxes were conducted, with which numerical models were established and validated. Factors influencing the mitigation effectiveness, such as the crushing strength and thickness of foam concrete, loading density, are examined and discussed in detail. It is found that for typical loading density, applying foam concrete layer effectively mitigates confined blast. The protection effectiveness in terms of steel box deformation improves with increasing foam concrete crushing strength and thickness. Ineffective or even negative mitigation may occur if the foam concrete layer is insufficient, which should be identified and avoided.

Time-history blast response and failure mechanism of RC columns using Lagrangian formulation

Structural behavior of RC structures under explosive loads is an emerging field of research especially RC columns since the damage of RC columns can lead to progressive collapse. Most research works investigated and concentrated on the behavior of RC columns when exposed to far-field detonations (FFD). A limited study is available on the effects of near-field detonation (NFD) and close-in detonation (CID) on the behavior of RC columns. Hence, the main purpose of the current research is to investigate the influence of different types of detonation scenarios on the dynamic behavior of RC columns. The influences of extreme loading conditions on the columns are defined by using Lagrangian analyses in LS-DYNA. Validation of the numerical model is implemented by comparing the numerical analysis results with UFC 3–340-02 Standard. It is shown that the model yields a reliable prediction of damage on all RC columns. Intensive studies are performed to evaluate the influences of various scaled distances on the dynamic behavior of the columns. The results demonstrated that when the columns are subjected to CID explosions, they undergo the maximum pressure and the columns fail due to severe impulsive regime loading. The results revealed that when the scaled distance is in the CID range, the peak blast load increases but the duration of the positive phase of the blast wave decreases resulting in higher amplitude, lower-duration shock pulse and when the scaled distance is in the FFD range, the peak blast load decreases but the duration of the positive phase blast wave increases resulting in lower amplitude, longer-duration shock pulse. Also, the results show that increasing the scaled distance in RC columns subjected to NFD and FFD detonations resulted in a further decrease in the peak deflection histories and damage degree of RC columns in comparison to CID explosions. The current investigation and the outcomes can be utilized for evaluation of the effect of an explosion on the RC columns.

Blast responses of carbon-fiber reinforced polymer tubular columns filled with seawater sea-sand concrete

Concrete-filled fiber-reinforced polymer tubular (CFFT) columns are advanced structures in civil engineering due to their advantages of high strength, good corrosion resistance, and strong stability. In this study, four groups of columns were designed, with three groups of CFFT columns cast with carbon-fiber reinforced polymer (CFRP) tube and seawater sea-sand concrete (SSC) reinforced with glass fiber reinforced plastic (GFRP) bars and one group of reference SSC columns. Quasi-static compression and field explosion experiments were conducted to investigate their quasi-static and dynamics mechanical performances. The damage of exploded columns was evaluated by direct radiography (DR) inspection and residual bearing capacity testing. The quasi-static compression capacity of the CFFT column is about twice of the summation of the load bearings of the CFRP tube and the SSC column with the help of the constraint effect of the CFRP tube. An improved model was proposed to predict the compression capacity of the CFFT column considering the strength of the CFRP tube. The CFRP tube attenuates the spalling failure of SSC columns and transfers the damage to concrete tensile crack and CFRP damage. The innovative CFFT column filled with GFRP bars reinforced SSC exhibits immense potential in marine protective structures.

Response Control of Structures with Friction Dampers under Blast Loading

Introduction: This study investigates the performance of the surface blast load acting on Moment Resistance Frames (MRF)with a novel slip load friction damper. Recently the world is facing terrorist activities that lead to the damage of the structures, including commercial, industrial, and public buildings. Methods: These structures should be protected by using control devices. Friction damper is a passive damping device that absorbs maximum energy released during vibrations. Blast loads are calculated based on empirical equations.In this study, single slip and double slip load friction dampers considering the hysteresis loops are used for controlling the response of the MRFs exposed to blast loadings. Results: The four storey, eight storey, and twenty storey MRFs with surface blast responses are controlled by using single and double slip load friction dampers. The response includes displacement, accelerations, velocity, storey drift, storey drift ratio, pressure impulse curve, etc. The torsional effect with two dimensions is considered for the high-rise structure as well. Conclusion: It was concluded that using friction dampers plays a vital role in controlling the response of MRFsunder blast loadings.

Blast responses of shallow-buried prefabricated modular concrete tunnels reinforced by BFRP-steel bars

This paper reports the anti-blast performance of shallow-buried prefabricated modular tunnel reinforced by basalt fiber-reinforced polymer (BFRP) -steel bars. Three concrete arch members with steel bars and three concrete arch members with BFRP-steel bars were fabricated, with the other arch parameters kept constant. The three identical arches were assembled into an integral structure and then buried in soil for field anti-blast experiments. Through the experiment, the pressure on the vault, the displacement and acceleration of the vault, the strain in the reinforcement bars and the macroscopic damage of the arches under the blast load were determined. To evaluate the damage of the arch tunnel, a residual load-bearing capacity test was conducted on the arch members after the explosion experiment. The experimental results showed that the BFRP-steel bars reinforced concrete arch exhibited a higher load-bearing capacity and more safety redundancy than the steel bars reinforced concrete arch, and that the BFRP-steel bars could inhibit the occurrence of concrete cracks to a certain extent. A comparison between the arches assembled at different positions showed that the prefabricated modular tunnel can be simplified directly as a two-dimensional arch structure under the blast load for analysis and calculation.

Dynamics of pulse-loaded circular Föppl-von Kármán thin plates- Analytical and numerical studies

Materials such as modern armour steel, benefit from appreciably high elastic energy storage capacity prior to failure. Such a capacity contributes to absorption of the impulse generated during an extreme pulse pressure loading event such as a localised blast. As the plate deforms within the bounds of the elastic region without plastic dissipation, the probability of catastrophic failure is mitigated while large deformations compared to conventional metallic panels are encountered. No studies have proposed, to date, a closed-form solution for nonlinear elastic response of thin circular plates subject to localised pulse loads.The present work aims at deducing, from the minimization of the Föppl-von Kármán (FVK) energy functional, explicit solutions for the response of dynamically (pulse) loaded thin clamped circular plates undergoing large deformations. The solutions were derived from a presumed kinematically admissible displacement field together with an associated stress tensor potential as an infinite polynomial series, which was truncated into a multiplicative decomposition of temporal parts and spatial parts, representative of a Multiple Degrees-of-Freedom (MDOF's) system.In the case of static loading, using the Frobenius method, an exact recursive solution to each mode of defamation was obtained. In the event of dynamic loading, useful expressions for stress tensor components were delineated, corresponding to a multimode multiplicative product, and a series of coupled Ordinary Differential Equations (ODE's) were derived, using the Ritz-Galerkin variational method. The explicit solutions were sought using the Poincaré-Lindstedt (PL) perturbation method. The closed-form solutions obtained were corroborated with FE results including the Fluid-Structure Interaction (FSI) effects and showed convergence when the first few modes were considered. The influence of higher modes, however, on the peak deformation was negligible and the solution with 3 DOF's conveniently estimated the blast response to a satisfactory level of precision. The influence of element type on the response was also examined and discussed in the context of the problem.

Full static resistance of castellated steel beams with hexagonal web openings for blast response predictions

To avoid structural collapses by explosions and terrorist attacks, castellated steel beams (CSBs) could become an alternative to parent steel beams (PSBs) in structures due to high energy absorption capabilities, which offered through a combination of high strength and ductile response. The static resistance function, obtained by either experiments or FE modeling, is considered an important item of data in calculating the dynamic response of a system using Single Degree of Freedom models. This research estimated and promoted the static resistance of CSBs to enhance their ductility and dissipate blast energy through large deformation kinematics. Quasi-static experiments on CSBs were performed to investigate the effect of end connections and different strengthening techniques (closed holes and vertical stiffeners) on the static resistance of CSBs. Load-deflection and strain data were recorded for each specimen up to failure. Moreover, a Finite Element (FE) model was developed and verified against tests. Good matching through all phases of resistance was obtained between the FE and test results. An extensive parametric study was carried out to predict the full static resistance of CSBs under the effect of cross-section geometries. Different ranges of spans were investigated to determine the minimum effective span-to-depth ratio. By providing vertical stiffeners as well as bolted head plate connections, CSBs obtained a larger capability of deformation through the tension membrane stage to resist blast loads under simultaneous high tension and shear forces.

A multi-hazard-based design approach for LRB isolation systemagainst explosion and earthquake

Base isolation system is originally known as one of the most efficient earthquake-resistance control systems. Isolated strategic structures may also experience terrorist attacks during their lifetime. In this paper, a design method is proposed for lead rubber bearing (LRB) isolation system under multi-hazard of explosion and seismic. This method is based on transforming the design problem into an optimization problem. The seismic response of structure has been defined as objective function while the constraints have been applied on its blast response. To validate the effectiveness of the proposed design method, LRB is designed for controlling a four-story steel moment-resisting building. For comparison objectives, this control system has been also designed under seismic hazard without paying attention to its blast performance. The results show that the earthquake-based optimally designed LRB has effective performance under seismic hazard whereas its blast performance is not as good as its seismic performance. Therefore, this control system cannot be considered as a well-designed control system for multi-hazard. The multi-hazard-based optimally designed LRB shows excellent performance under both blast and seismic loadings, so the proposed design method can be introduced as an effective design approach for LRB under multi-hazard of explosion and seismic.

Phosphoproteomic Characterization of Primary AML Samples and Relevance for Response Toward FLT3-inhibitors.

Phosphoproteomic Characterization of Primary AML Samples and Relevance for Response Toward FLT3-inhibitors.

Macrophage Involvement in the Response of Acute Myeloid Leukaemia to Chemotherapy

Acute myeloid leukemia (AML) is a clonally heterogeneous neoplasm with poor survival rates. Although chemotherapy often leads to clinical remission, the relapse rate of AML is very high and usually fatal. Chemotherapy is usually effective at debulking AML blasts however a small population capable of re-initiating the leukemia (LIC) survive ultimately causing relapse. Mouse models of AML suggest that LIC are protected from chemotherapy by a protective niche similar to hematopoietic stem cell (HSC) niches. As 1) bone marrow (BM) macrophages are key regulators of HSC niche function and 2) tumor-associated macrophages promote chemotherapy resistance in several models of solid tumors (e.g. breast, lung & ovarian) we investigated a potential role of BM non-malignant macrophages in promoting chemoresistance of AML blasts.Using a mouse model of AML driven by the MLL-AF9 oncogene in which mouse HSC are transduced with MSC-MLL/AF9-ires-GFP and transplanted into syngeneic recipients, we examined how AML progression alters the phenotype of non-malignant GFP-negative BM macrophages by flow cytometry. 18 days post-transplant, GFP+ leukemia burden in the BM was in the 40-60% range. In non-malignant GFPneg BM macrophages, cell surface expression of MHC class II, CD80, L-selectin and neuropilin-1 was significantly decreased suggesting that AML blasts alter the function of BM macrophages.To determine whether BM macrophages could have any role in AML response to chemotherapy, we first determine whether non-malignant BM macrophages were depleted in vivo by treatment with cytarabine (5 days, 100mg/kg) and doxorubicin (3 days, 1mg/kg). Two days after cytarabine+doxoR treatment, most CD11b+ F4/80- Ly6G+ granulocytes and CD11b+ F4/80+ CD169- monocytes were ablated from the BM with 0.1% granulocytes and 1.0 % monocytes surviving after treatment. In contrast CD11b- F4/80+ CD169+ VCAM1+ macrophages were the most resilient myeloid cells in the BM with 9.5% still present 2 days after chemotherapy.To further investigate a possible role of these chemotherapy-resilient CD169+ macrophages in promoting response of AML blasts to chemotherapy, we transplanted MLL-AF9 leukemia cells generated with wild-type HSC into CD169DTR/WT mouse recipients in which one CD169 allele is knocked-in with human diphtheria toxin receptor (DTR). This enables specific depletion of CD169+ macrophages in vivo by injecting diphtheria toxin (DT). In this model, DT treatment targets host CD169+ macrophages but not the AML blasts as they do not contain the DTR knock-in. In the absence of chemotherapy, depletion of recipient CD169+ macrophages did not alter leukemia burden in the BM, spleen or blood 48 hours post depletion and did not alter mouse survival (median survival 29-30 days in both CD169-DTR and WT recipients treated with DT or saline).However when cytarabine + doxoR were administered 48 hours after DT administration, median survival of CD169-DTR recipients was significantly increased to 39.5 days compared to wild-type recipients 35 days, p<0.001. Furthermore leukemia burden in both the blood and spleen was significantly reduced.To determine whether CD169 could by itself mediate lower response of AML to chemotherapy, we transplanted MLL-AF9 cells generated from WT HSC into CD169DTR/DTR mice which are knocked-out for both CD169 alleles. Deletion of both CD169 alleles in recipient mice did not change mouse survival in response to chemotherapy in the absence of DT. Therefore absence of CD169 is not sufficient to prolong mouse survival in response to chemotherapy.In conclusion, non-malignant CD169+ macrophages may protect MLL-AF9 leukemia blasts from the cytotoxic effects of cytarabine and doxorubicin. The mechanisms of this chemoprotection remain to be determined but do not involve a direct effect of CD169 on AML blasts. DisclosuresNo relevant conflicts of interest to declare.

Flow Cytometric Minimal Residual Disease As Risk Stratification Tool in Younger Adults with NPM1 Wild Type Standard Risk Acute Myeloid Leukemia

Response to induction therapy is a powerful prognostic indicator in acute myeloid leukemia (AML). Measurable/minimal residual disease (MRD) assays are being increasingly incorporated into response assessment; however, their value as a surrogate for long-term outcome remains unclear because of assay limitations and the effect of post remission therapies. This is particularly the case for the molecularly heterogeneous NPM1 wild type standard risk patients for whom treatment decisions, including predicting the benefit of allogeneic stem cell transplantation (SCT), are particularly challenging. We investigated the effect on outcome of MRD status compared to other response criteria after each cycle of induction for NPM1 wild type (wt) standard risk patients and other risk groups in a cohort of younger AML patients.Patients and MethodsAs part of the UK NCRI AML17 trial (ISRCTN55675535) for patients with AML or high risk MDS up to the age of 60, prospective flow cytometric MRD (MFC-MRD) monitoring was performed after each course of induction. Any level of MRD detected was considered MRD+ (sensitivity thresholds: ~0.02% by tracking diagnostic leukemic aberrant phenotypes/LAIP, ~0.05-0.1% by “different-from normal” blast LAIP). Clinicians were not informed of MFC-MRD results. Following cycle 1 of induction with daunorubicin/ara-C based therapy, patients were allocated a risk group by a validated score (comprising cytogenetics, WBC, age, secondary disease, blast response to cycle 1 and mutation status). Standard risk patients including ITD wt/ NPM1 wt received a second daunorubicin/ara-C induction with some proceeding to SCT after 1 or 2 consolidation cycles (high dose ara-C).Results2450 non APML patients, median age 51, randomised 4/09 to 12/14, contributed data. For the total cohort, 5 year overall survival (OS) excluding early deaths was 52% for those achieving CR/CRi vs 31% for those not in CR (p<.001).Post cycle 1 (C1) responses were categorised as resistant disease (RD), partial remission (PR) and CR/CRi by clinicians, with CR/CRi subdivided by MFC-MRD assay into MRD+ and MRD-. RD vs PR vs MRD+ vs MRD- frequencies were 15% vs 14% vs 40% vs 31% for all patients with response data (n=1443), 5% vs 7% vs 45% vs 43% for good / standard risk (n=785), 10% vs 8% vs 47% vs 35% NPM1 wt standard risk (n=320).Post C1 response was prognostic for survival: OS for RD vs PR vs MRD+ vs MRD- were 25% vs 36% vs 43% vs 63% all patients; 33% vs 49% vs 51% vs 70% good/standard risk and 28% vs 38% vs 47% vs 59% NPM1 wt standard risk. (p<.0001 throughout). For NPM1 wt standard risk as well as good/standard risk patients adjusted analyses confirmed significant OS differences between C1 RD vs PR or MRD+ but not PR vs MRD+. Results were similar when censored at SCT.Post C1 best response was CRi for 39/446 MRD- vs 49/575 MRD+ overall (11/111 vs 8/149 for NPM1 wt standard risk). C1 CRi was associated with reduced OS overall (39% vs 53% CR, p=.002) and in MRD+ (19% vs 45% CR, p=.001) but not for MRD- patients. OS for NPM1 wt standard risk MRD+ was 25% CRi vs 43% CR (p=0.4). No significant difference was detected for 5 year cumulative incidence of relapse (CIR).The effect on outcomes of MRD status post cycle 2 (C2) for the 806 patients in CR/CRi with MFC-MRD data appeared greater (relapse HR 1.88(1.50- 2.36), p<0.001; OS HR 1.77(1.41-2.22) p<0.001)than C1 (relapse HR 1.70(1.40- 2.06), p<0.001; OS HR 1.50(1.23-1.84) p<0.001). MRD+ levels of ≥0.1% predicted highest CIR in NPM1 wt standard risk patients at C1 (CIR 71%) and C2 (CIR 89%) but any MRD+ at C2 reduced OS (32% vs 63% MRD-, p=0.003) and OS censored at any SCT (35% vs 88%). The effect of CR vs CRi was smaller post C2 although outcomes were still worst in CRi/MRD+ve patients.Of 204 NPM1 wt standard risk patients with C2 MRD data 83 had an allograft (44 in CR1: 29 MRD-, 15 MRD+). In Mantel-Byar analyses, although numbers were small, there was a suggestion that transplant could be considered in MRD +ve (HR 0.72 (0.31-1.69)) but not MRD -ve patients (HR 1.68 (0.75-3.85); p-value for interaction p=0.16).ConclusionMRD status by MFC refines response criteria at induction time-points to differentiate NPM1 wild type standard risk patients with poor outcome and helps define a group of patients who may benefit from SCT in CR1. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

High strain rate response of laminated glass interlayer materials

During a blast event, the polymeric interlayer of laminated glass used in windows and curtain walls plays an essential role in protecting buildings and occupants. In this research, the dynamic constitutive behavior of ultraviolet (UV) cured one-component acrylic resin (UVEKOL-S), Polyvinyl butyral (PVB), and virgin PVB extracted from heat strengthened laminated glass panes were investigated at an average strain rate of 30–40 s−1 using impact drop-weight apparatus. An analytical procedure was developed to simulate the drop weight device and calculate the drop height required for a certain strain rate. A new technique was used to investigate the mechanical properties of PVB, and UVEKOL-S before and after the breakage of the laminated glass, including each material energy absorption capacity. The results show that both PVB and UVEKOL-S, at strain rates of 30–40 s−1, had an initial rise in strength. However, after the maximum stress point, both materials followed a noticeable difference in their response to failure. Comparing the high-strain and static results showed that the dynamic loading significantly affects the material response and the energy absorption characteristics of the interlayer materials, and subsequently, the blast response of laminated glass panels. Sufficient data was obtained from the tests to evaluate alternative approaches to modeling PVB and UVEKOL-S materials in the blast event.

A Pin1/PML/P53 axis activated by retinoic acid in NPM-1c acute myeloid leukemia.

Retinoic acid (RA) was proposed to increase survival of chemotherapy- treated patients with nucleophosmin-1 (NPM-1c)-mutated acute myeloid leukemia. We reported that, ex vivo, RA triggers NPM-1c degradation, P53 activation and growth arrest. PML organizes domains that control senescence or proteolysis. Here, we demonstrate that PML is required to initiate RA-driven NPM-1c degradation, P53 activation and cell death. Mechanistically, RA enhances PML basal expression through inhibition of activated Pin1, prior to NPM-1c degradation. Such PML induction drives P53 activation, favoring blast response to chemotherapy or arsenic in vivo. This RA/PML/P53 cascade could mechanistically explain RA-facilitated chemotherapy response in patients with NPM-1c mutated acute myeloid leukemia.

Testing the blast response of foam inserts for helmets

Modern era combat helmets have different iterations and configurations to offer greater protection from blunt impact or ballistic penetration to suit the theatre of operation, although there are currently no standards for blast protection. Moreover, incorporation of blast protection into the same constrained mass-volume envelope is extremely challenging as there is very little space for a material to absorb or dissipate the shockwave. Foam padding is fitted in contemporary combat helmet designs for comfort and standoff purposes. Examples were subjected to blastwaves generated from an air-driven shocktube, along with open cell polyurethane foam specimens of varying pores per inch and thicknesses to. Whilst the range of samples tested did not afford any superior blast mitigation behaviour over the foam already present in helmets, they exhibited comparable performance with a lower mass. There also appears to be positive correlation between increased mass and increased impulse transmitted through the foam. The literature suggests that multiple mechanisms of damage for blast induced mild Traumatic Brain Injury (bTBI) can be caused by the helmet itself, therefore additional protection from a blunt or ballistic impact may increase the risk of damage from a blast insult.

Dynamic response of polyurea coated thin steel storage tank to long duration blast loadings

Cylindrical steel storage tanks are often under the threat of long duration blast loadings induced by the explosion of flammable vapor clouds, and therefore the blast response and mitigation method of the tanks are of great importance to related industries. In the meantime, polyurea coating material, which has been proved to be effective in the blast mitigation of different structures, is employed in this study for the protection of steel storage tanks. Gas blast experiments, as well as numerical and theoretical models, are utilized to investigate the response and energy absorption mechanism of steel tanks and analyze the effect of polyurea coatings. The numerical results showed that the bending of the plastic hinge lines and the tension of the connect zone of the cylindrical shell are the main energy absorption ways of the tank. The modified beam-on-foundation model is then established and verified and the model indicates that the polyurea coatings mainly influence the displacements of the tanks by increasing the area density and bending moments of the tanks. Quantitative analysis on the effect of polyurea is conducted utilizing the response spectrum of the tank’s equivalent system and the range of displacement reducing ratio caused by polyurea and the appropriate spraying strategy of polyurea are acquired accordingly. At last, further numerical simulations are performed and give results that validate the theoretical predictions.