Flame Spread Research Articles

Quality of Fine Yarns from Modacrylic/Polyacrylate/Lyocell Blends Intended for Affordable Flame-Resistant Underwear.

Flammability testing of undergarments is a topic that is often overlooked and rarely on the list of textiles to be tested for fire safety. However, it is particularly important for professionals exposed to fire risk to investigate the flammability of underwear as its direct contact with the skin can be critical to the extent and degree of skin burns. This research focuses on the suitability of affordable blends of 55 wt.% modacrylic, 15 wt.% polyacrylate, and 30 wt.% lyocell fibres that have the potential to be used for flame-resistant underwear. The influence of modacrylic fibre linear density (standard and microfibres), ring spinning processes (conventional, Sirospun, and compact), and knitted structure (plain, 2:1 rib, 2:1 tuck rib, single pique, and triple tuck) on their properties required for thermal comfort in high-temperature environments was investigated. Scanning electron and optical microscopy, FT-IR spectroscopy, mechanical testing, moisture regain, water sorption, wettability, absorption, DSC, TGA, and flammability were tested to assess the desired suitability. The wetting time (5-14.6 s) and water absorption time (4.6-21.4 s) of the knitted fabrics have shown excellent ability to transport and absorb water compared to the knitted fabrics created from a conventional blend of 65% modacrylic and 35% cotton fibres. The afterflame and afterglow times of less than 2 s met the criteria for non-flammability of the knitted fabrics according to the limited flame spread test method. The results show that the investigated blends have the potential to be used for affordable flame-retardant and thermally comfortable knitted fabrics for underwear.

Heat transfer and spread characteristics of continuous ethanol spill fires on sand substrates

Spill fire is common in industry, with the characteristics of large burning area and difficult to extinguish. To study its mechanism more deeply, a series of experiments of ethanol spill fire were carried out on sand substrate. The flame spread distance was measured, and the heat feedback and burning rate were analyzed. The experimental results showed that 0.25 mm sand made the proportion of heat conduction feedback in the quasi-steady stage reach about 70% of all thermal heat feedback, and the steady burning rate also reached the maximum value. With the increase of sand size, the proportion of heat conduction feedback decreased, the heat convection feedback gradually dominated, and ultimately the steady burning rate decreased first and then increased. This showed that sand affected the heat transfer in the quasi-steady stage of spill fire by changing the heat transfer process and the proportion of three modes of heat transfer, thus changed the steady burning rate. Furthermore, the influence of sand on the spread of ethanol in terms of mass transfer was also analyzed. For the initial spread stage, the obstructive effect of sand on the fuel spread was quantified based on Darcy's law. It was found that the obstructive capacity of sand on fuel spread had a quadratic relationship with its specific surface area.

Analysis of Fire Simulation on Polyurethane Foam Using FDS in a University Meeting Room

The polyurethane foam material is commonly used and marketed in two forms, namely flexible and rigid. Flexible foam is used as a cushion, with various applications for commercial products such as chair support. Therefore, this study aims to describe the occurrence of a fire situation in a university room filled with many polyurethane foam chairs. It also aims to provide awareness regarding potential flame hazards, by using a fire modelling method with FDS. The results showed that fires on PU foam materials produced a high HRR and a wide spread of flame and smoke. From this context, the harmful effects of the fire on the room occupants were emphasized. The results obtained are expected to support the theory of compartment fire, flame distribution in solid materials, PU Foam inferno behaviour, etc. It is also expected to provide additional fire protection and evacuation training for room occupants.

Functional assignment of technological accessories for woodworking

Forming a heat and sound insulation board from wood using non-combustible binders can increase the fire protection of the material by forming a protective layer of coke. This will make it possible to develop a new type of fireproof roofing products for building structures. It is not always advisable to treat the surface of a heat and sound insulation board with fireproof coatings, since after prolonged thermal exposure, the combustion stage can be transferred to the interior of the material by smoldering. Therefore, the manufacture of fire-resistant heat- and sound-insulating wood materials, the study of fire protection and the impact of their components on this process is an unresolved component of ensuring the fire resistance of building structures. And, accordingly, they determine the need for such research.
 The paper presents the results of research into the process of protecting wood wool boards with binders based on fire-resistant coatings. Tests on model samples of a wooden board showed that the material based on wood wool and an inorganic binder is characterized by heat absorption and inhibition of oxidation in the gas and condensed phase and the formation of a thermally protective ceramic layer on the surface of the wood. Experimental studies have confirmed that a material based on wood wool and an inorganic binder at a ratio of 1:1 refers to combustible materials, since its smoldering was recorded during exposure to temperature. So, by thermal action for 90 s, the material ignited and the flame spread over the first three zones for 41 s. On the other hand, an increase in the amount of an inorganic-based binder and the use of an organic-mineral binder does not lead to a material fire. In this case, the maximum temperature of the flue gases was about 120 °C, and the flammability index was 0 due to the decomposition of fire retardants under the influence of temperature with the release of incombustible gases, which inhibit the oxidation of the material and significantly increase the formation of a heat-protective layer of coke on the surface of the material. This leads to inhibition of heat transfer of the high-temperature flame to the material. Due to this, it became possible to determine the conditions of fire resistance of the material by forming a barrier for thermal conductivity. The obtained results indicate the possibility of targeted regulation of high temperature transfer processes to organic material by using special binders for wood products.

Use of calcium chloride to enhance the efficacy of polyamidoamines as flame retardants for cotton

The role of metal ions in improving the flame resistance of cotton prompted to investigate whether adding CaCl2 to the glycine-derived polyamidoamine M-GLY, an excellent intumescent flame retardant for cotton, increased its efficacy in this respect. Thermogravimetric analysis demonstrated a superior thermo-oxidative stability of cotton when treated with M-GLY/CaCl2 mixtures, particularly above 550°C, compared to cotton treated with either M-GLY or CaCl2, suggesting that they act synergistically. In horizontal flame spread tests, M-GLY/CaCl2 coatings proved to be even more efficient than M-GLY coatings. In vertical flame spread tests (VFSTs), where M-GLY failed to protect cotton even at add-ons >30%, M-GLY/CaCl2 coatings with add-ons 7% and 2%, respectively, inhibited cotton ignition producing only modest afterglow, and leaving an 82% residue. No other amino acid-derived polyamidoamine, except those containing disulfide groups, has proved as efficient in VFSTs, even at much higher add-ons. The set of data reported here prompts that the ionic interactions of calcium ions with the carboxylate groups of M-GLY induce the formation of even larger amounts of char compared to M-GLY and lets envisaging a synergistic action of these two components. This finding paves the way for the study of new polyamidoamine-based organic/inorganic flame retardants for cotton.

Flame-Retardance Functionalization of Jute and Jute-Cotton Fabrics.

Jute is a ligno-cellulosic natural fiber that ranks second in terms of the volume of cellulosic fibers and is extensively utilized for technical textile applications. The goal of this study is to determine the flame-retardance (FR) properties of pure Jute and Jute-Cotton fabrics treated with Pyrovatex CP New at concentrations of 90% (owf), M:L: 1:7. Both fabrics exhibited a substantial improvement in flame-retardancy. After the ignition period, the recorded flame spread time in both FR treated fabrics was zero seconds; whereas for untreated Jute and Jute-Cotton fabrics, the flame spread time was measured 21 s and 28 s, respectively, to burn their entire length (15 cm). Within these flame-spread times, the length of the char was 2.1 cm and 2.57 cm in the Jute and Jute-Cotton fabrics, respectively. After FR finishing, on both fabrics in the warp and weft directions, the physico-mechanical properties significantly decreased. The deposition of flame-retardant finishes on the fabric surface was determined by Scanning Electron Microscope (SEM) images. According to Fourier Transform Infra-Red Spectroscopy (FTIR) analysis, the flame-retardant chemical had no effect on the inherent properties of the fibers. Thermogravimetric analysis (TGA) analysis revealed that FR treated fabrics had early degradation, resulting in the formation of more char than in the untreated samples. After FR treatment, both fabrics showed a significant improvement in residual mass (more than 50%). Although the formaldehyde content observed in the FR treated samples was significantly greater, it was still within the permitted limit formaldehyde content in textiles intended for outerwear and not worn next to the skin. The results of this investigation demonstrate the potential use of Pyrovatex CP New in jute-based materials.

Numerical study of transverse hydrogen injection in high-speed reacting crossflow

A high-speed compressible solver capable of solving detailed chemical reaction mechanisms is developed by coupling the open-source computational fluid dynamic toolbox OpenFOAM® and Cantera 2.5.0. A sonic hydrogen jet discharging from a circular injector into a high enthalpy supersonic crossflow over a flat plate is selected as a test case for the developed solver. The incoming boundary layer is laminar, and an adverse pressure gradient-induced transition is expected due to transverse injection. The test case is selected to serve two purposes. First, to validate the developed solver. Second, to inspect the capability of Reynolds-Averaged Navier–Stokes (RANS) in predicting the flame characteristics in high-speed flows involving laminar to turbulent transition. The present study features three-dimensional RANS simulations with Shear Stress Transport (SST) k–ω and Langtry–Menter SST k–ω turbulence models, with three values of inlet turbulent intensity: I = 0.5, 1, and 2. Analysis showed that laminar to turbulent transition plays a significant role in the resulting flame structure. A fully turbulent SST k–ω model showed several discrepancies from the experiment, especially near the boundary layer. On the other hand, the Langtry–Menter SST k–ω model predicts transition onset and hence the flame structures accurately. Furthermore, the transition onset and the flame structure strongly depend on I. The low-velocity recirculation regions near the injector aid in flame stabilization upstream of the injector. At the same time, the horseshoe vortex dictates the flame spread in a spanwise direction. The reflected shock–boundary layer interaction helps in flame stabilization downstream of the injector.

Synthesis and characterization of an intumescent halloysite based fire-retardant epoxy system

In this research, a halloysite-based nitrogen-phosphorous fire retardant epoxy system was evaluated. The synthesized melamine phosphate in combination with pentaerythritol as an intumescent fire retardant which was effective in previous studies was introduced. To achieve a strong and thermally stable char residue a tubular high aspect ratio halloysite nanotube to make bridgeable network and reducing flame spread as a promising reinforcing nanoclay was proposed. The present study focuses on investigating the fire retardant capabilities of partially cured melamine formaldehyde resin that has been used to cover fire retardant additives. The synthesized fire retardant additives were characterized by spectroscopic, microscopic analysis, etc. The synthesized fire retardant additives had an excellent effect on fire retardancy of epoxy resin and the strength of residual char. Thermogravimetric analysis data showed that suitable amount of halloysite had positive effect on the char residue to protect the substrate at high temperatures. Cone calorimetery test showed that the epoxy based fire retardant sample was successful to release heat slowly, and slow down the burning process by the formation of an efficient char on the surface of the substrate. The total smoke released by epoxy based fire retardant sample was 1469.1 m2/m2 while that of neat epoxy was 5589.6 m2/m2.

Micro-explosive combustion and flame spread of Jatropha oil/2, 5-dimethylfuran (DMF) blended fuel droplet array

The micro-explosive combustion and flame spread characteristics of a multi-component fuel droplet array are investigated using high-speed backlight imaging technique. The multi-component blends consist of 2, 5-dimethylfuran (DMF) as a lower volatile component, while Jatropha oil is used as the higher volatile constituents. Three droplets (droplet array) with the same diameter are horizontally arranged at equal intervals using fiber support method. The effects of normalized droplet spacing (S/d0) and DMF concentration on multiple droplets micro-explosive combustion and flame spread are also analyzed. The results show that the interaction between multiple droplets combustion can not be ignored under small S/d0. It increases with the increase of DMF concentration and the decrease of S/d0. When the S/d0 is constant, the interaction between droplets depends on the duration of simultaneous combustion of multiple droplets and the number of droplets surrounded by the same flame. Due to the micro-explosion, the average flame spread velocity of Jatropha oil-DMF blended fuel droplet array decreases monotonously with S/d0 in normal gravity, which is different from that in microgravity. Four flame spread modes of droplet array containing micro-explosion are found: full-envelop flame, sequential full-envelop flame, semi-envelop flame to independent flame and independent sequential flame.

Influences of the presence of char layer on flame spreads over wood with different thermal thickness

Influences of the presence of char layer on flame spreads over wood with different thermal thickness

Multi-scale investigation of factors influencing moisture thresholds for litter bed flammability

Fuel moisture is important to flammability. Vegetation communities vary in their moisture thresholds for ignition and fire spread. Different factors, operating at distinct spatial scales (litter vs. vegetation community) may be responsible for these variations in moisture thresholds. The relative importance of these factors at each scale remains unquantified. Our study sought to examine what factors influence moisture thresholds for flammability across two spatial scales (point vs. plot). Litter samples were collected repeatedly over one fire season (2020–21) from selected sites within temperate eucalypt forest along an aridity gradient in south-eastern Australia. Samples were reconstructed then burnt under controlled conditions. At the point-scale (0.05 m2), we quantified flammability as the probability of sustained ignition, flame spread rate and flaming duration. At the plot-scale (400 m2), we quantified flammability as the proportion of sustained ignitions. At the point-scale, moisture thresholds varied with leaf cover on the surface of the litter bed for ignition and leaf size for flame spread rate. At the plot-scale, vapour pressure deficit (VPD) was the best predictor of ignitability and moisture thresholds varied with aridity. Wetter parts of the landscape had a higher VPD threshold for ignition than more arid parts, meaning they were available to burn less often. The relationship between leaf cover and ignitability observed at the point-scale was overwhelmed by the effect of moisture at the plot-scale. Variations in ignitability between vegetation communities were driven by aridity-induced changes in canopy cover and its effect on litter moisture. Ignitability models based on VPD and aridity could be used to predict ignitability now and into the future, given anticipated increases in VPD under climate change.

Numerical Simulation of Downward Flame Propagation in Discontinuous Region of Solid Fuel

This paper presents a numerical model that investigates the characteristics of flow, heat, and mass transfer on downward flame propagation in the discontinuous region of solid fuel. Simulations were carried out for various discontinuous distances to analyze the morphology of the flame front and the competition between the “jump” of flame spread and heat transfer from the flame to the unburned area. The results demonstrate that there is a “jump” in the flame propagation in the discontinuous zone, with the flame front exhibiting a defined “acute angle” that undergoes a process from large to small during the flame spreading in the discontinuous area and deflects towards the discontinuous area of the material. The temperature in the discontinuous zone reaches a peak, and the average flame spread rate initially increases and then decreases with the increase of discontinuity distance until the flame spread stops. The study provides valuable insights into the growth and development of fires involving discretely distributed combustible materials.

Effect of solid surface curvature and wall heat loss on the downward flame spread along the edge of thin PMMA sheets

Flames propagating along the sample edges (edge flame) will transform two-dimensional flame spread into three-dimensional flame spread, causing a significant interference with results of material flammability test. A potential method to minimize above effect is utilizing an inert wall to inhibit the side surface of sample with a designed air gap distance. In this work, the downward flame spread along the sample edge with various air gap distances is systematically studied. Cast PMMA with thicknesses from 0.4 to 2.5 mm were used as samples. The general trend of flame spread rate (FSR) at edge with respect to air gap distance can be summarized into three regimes: when the air gap distance is less than 2 mm, the edge flame is quenched by wall heat loss, and the overall flame spread behavior is two-dimensional. Then, the edge flame appears after the air gap distance exceeds 2 mm, resulting in a sharp increase in FSR. This critical air gap distance for the onset of edge flame is less sensitive to the sample thickness. Finally, as the air gap distance continues to increase, the FSR gradually approaches the asymptotic value of the uninhibited sample. With the increase in air gap distance, thermally-thin assumption loses validity as a result of the reduction in residence time of solid phase (larger FSR). To interpret the general trend of FSR with respect to air gap distance, a modified flame spread model based on conventional thermal theory is developed. The effect of air gap distance on flame spread along sample edge is characterized by two correction factors, one of which describes solid surface curvature at sample edge, the other of which is the effective flame temperature considering the heat loss from the spreading flame to the metal wall. The new model well reproduces the experimental results, and further supports the significance of heat loss in the trend of flame spread rate. This work helps to understand the flame spread mechanism under effects of solid surface curvature and heat loss, while also providing scientific support for optimization of material flammability testing standards.

An analysis of the sensitivity of the rate of buoyancy-driven flame spread on a solid material to uncertainties in the pyrolysis and combustion properties. Is accurate prediction possible?

In this study, upward flame spread over a combustible solid in a vertical corner configuration was simulated using two widely used computational tools – ThermaKin2Ds and the Fire Dynamics Simulator (FDS) – and predicted sensitivity of fire growth dynamics to variations in material properties was examined to determine which ones carry measurement uncertainties that translate into the largest errors in predicted behavior. The nominal value of each material property was calculated as the average of measured values of a balanced set of 26 materials that represent the combustible polymeric solids widely used in industrial, transportation, and construction applications. The upper and lower boundaries of each property were defined based on an uncertainty quantification of each specific measurement. These average material properties and related uncertainties were determined based on an extensive literature review presented in this work.A measure of average flame spread velocity was defined (based on the time derivative of pyrolysis front location) as the model output to characterize fire growth dynamics. Overall, ThermaKin2Ds and FDS generally demonstrate similar sensitivity to model inputs. For both simulation tools, uncertainties in reaction kinetics (Ea/ln(A)) and heat capacity of the virgin material, had the most significant effect on calculated average flame spread velocity, resulting in changes in this output (on average, for both simulation tools) of approximately 20%. FDS simulations also demonstrated a strong sensitivity to variations in heat of combustion when it was adjusted from its mean value to its lower or upper uncertainty bounds (17% change in average flame spread velocity; 2, 3 times as sensitive as ThermaKin2Ds results). In ThermaKin2Ds, an approximate 10% sensitivity in predicted average flame spread velocity was observed to variations in thermal conductivity of the virgin material, while in FDS this output demonstrated limited sensitivity to this parameter change. Uncertainties in the density of the virgin material and its char yield also showed a notable impact on predicted average flame spread velocity in both simulation tools. All other material properties considered in this work were found to demonstrate negligible influence on average flame spread velocity, which indicates that these parameters are measured with sufficient accuracy to deliver reasonably accurate predictions of flame spread dynamics.

On the radiation extinction of opposed flame spread over curved solid surface in low flow velocity conditions

The controlling mechanisms of the radiation extinction of the flame spreading over cylinders in low flow velocity conditions are investigated with an analytical approach. Attention is focused on the interaction among solid surface curvature, solid surface radiation, and gas-phase volumetric radiation heat loss in the flame spread process. The analysis uses a classical thermal model, which considers the heat balance on the unburned fuel surface near the flame front. A non-dimensional number that evaluates the effects of volumetric radiation heat loss and finite rate chemistry on the flame temperature is also proposed. It is found that solid surface radiation cannot be a dominant mechanism for the radiation extinction of a flame spreading over a thin cylinder. Furthermore, in the case of flame spread over a cylinder, flame spread rate significantly increases with decreasing opposed flow velocity due to curvature effect, thus the consideration of the relative gas flow velocity seen by the spreading flame becomes essential in low flow velocity conditions. However, when the volumetric radiation heat loss in the gas phase is taken into account in the thermal model, flame spread rate for a thin cylinder once increases with decreasing opposed flow velocity and then turns to decrease. As a result, the flame spread rate of a thin cylinder shows a peak value in low flow velocity conditions. This trend is in good agreement with previous microgravity experiments (Fujita et al., 2002 [1]). Moreover, the limit condition of flame spread appears as a bifurcation point where the stable and unstable solutions of flame spread rate coincide in the low flow velocity condition. The analytical results indicate that it is essential to consider the volumetric radiation heat loss in the gas phase to predict the flame spread over a curved surface in low flow velocity conditions.

Gliding Arc Plasma-Controlled Behaviors of Jet-Wake Stabilized Combustion in a Scramjet Combustor

A multichannel gliding arc (MCGA) plasma is used to control the jet-wake stabilized combustion in a Mach 2.92 cavity-based and ethylene-fueled scramjet combustor. Optical diagnostic methods (including high-speed photography, schlieren, and planar laser-induced fluorescence with acetone tracer) combined with plasma kinetic simulations and Reynolds-averaged Navier–Stokes/large-eddy simulations were employed to investigate the combustion behaviors. The results show that the flame is mainly located near the cavity leading edge and operated at the jet-wake stabilized mode. When the MCGA plasma is added at the upstream wall of the cavity leading edge, the vigorous region of the flame spreads upstream 6.5 times longer than the original one without the plasma. Once the plasma is turned off, the flame returns back to the cavity leading edge. The species (Nitrogen in the excited state) and hydrogen atoms produced by the plasma are favorable for igniting the flame near the plasma, and the average penetration depth of the fuel above the plasma is increased by about 10%. Intense combustion near the plasma occurs with higher pressure, establishing the recirculation zone with the boundary-layer separation. The combined effects of the reactive species produced, the elevated temperature, and the modified flowfield induced by the plasma contribute to the MCGA-controlled behaviors of jet-wake stabilized combustion.

Investigation of liquid fuel combustion processes in an electrostatic fieldе

Objective. The article presents the results of experimental studies on the effect of a high-potential electrostatic field on the combustion of liquid fuel. Method. Experimental studies were carried out on the developed laboratory installation, which makes it possible to ensure the combustion of liquid fuel in a high-potential electrostatic field with the possibility of changing the polarity. The change in the polarity of the applied voltage to the electrode system of the experimental setup led to an increase in the fuel burning rate in the first case, and to its attenuation in the second.Result. In this paper, studies have been carried out proving the effect of an electrostatic field on the burning rate and reducing the content of harmful components (soot and carbon monoxide) in fuel combustion purges. Based on the values of the fuel burning rate obtained as a result of the experiments, graphic dependences were constructed on the applied voltage, on which the areas of linear and non-linear changes in the combustion parameters were identified.Conclusion. The results of the research carried out can be used to create new highly efficient burners for liquid fuel boilers. The effect of reducing the burning rate can be used to create fire safety devices that block the spread of flame during a fire.

Numerical study of the firing, radicals and intermediates in the combustion process of a H2-assisted combustion DISI methanol engine

The firing, radicals and intermediates in the combustion process of a port-injection hydrogen (H2)-assisted combustion direct-injection spark-ignition (DISI) methanol engine were numerically simulated. The engine with port-injection H2 plus direct-injection methanol was tested at 1800 rpm with intake manifold absolute pressure of 68 kPa. AVL-Fire coupling the detailed methanol chemical kinetics modeling with 21 components and 84 elementary reactions was used to simulate in this study. The model calculation results agreed well with the experiments, and the average error is less than 3% and can guarantee other outcomes. The simulation results show that high added H2 ratio (RH2) has higher turbulent kinetic energy in the region closer to the combustion chamber wall. When RH2 is greater than 6%, the formation time of fire core is obviously shortened and the average flame propagation velocity is significantly increased. Increasing RH2, the generation speed and the peak value of H, O and OH radicals increase, and higher concentration of radicals accelerates the diffusion of combustion from the hot flame zone. OH radical is a key reactant, which always plays a decisive role in the process of methanol oxidation. Effect of added H2 on methanol oxidation reaction is reflected in accelerating the initial stage of combustion and ameliorating the intensity of reaction. The mass fractions of HCHO, HCO and CO, as the main intermediate products, all show a trend of increasing first and then decreasing with the crank angle (CA), and their peak values indicate the phase of the most violent reaction. The peak values of HCHO and HCO are all near the top dead center (TDC), which is consistent with the trend of H and OH radicals generation rate. The relationship between consumption rate of methanol and CA shows that the consumption rate of methanol at RH2 = 9% is the earliest and steepest, and most of methanol has been consumed by reaction before TDC. Added H2 accelerates the fire propagation, H2 dominates the process of radical formation and methanol chain reaction, the flame spread period is shortened rapidly, and the effect of added H2 to promote combustion is obvious.

Enhanced combustion characteristics of fuel‐rich propellant based on Al−Mg via GAP‐IPDI energetic thermoplastic polymer

AbstractIn this work, the energetic thermoplastic polymers were synthesized with different ratios of energetic prepolymer glycidyl azide (GAP) and isophorone diisocyanate (IPDI), and used as the binder to prepare fuel‐rich propellants based on Al−Mg. The results showed that energetic thermoplastic polymer enabled the fuel‐rich propellant a faster flame spread, greater flame strength, and a stronger injection effect of metal droplets. The weight loss (Δm) of the propellants increased with GAP content, while the weight loss rate (Dmax) increased similarly. The Δm increased from 7.92 % to 9.86 % and Dmax from −0.23 % ⋅ °C−1 to −0.35 % ⋅ °C−1 in the range 100–256.5 °C. The propellant with the highest GAP content (85GAP‐Prop) had the lowest apparent activation energy (150.77 kJ ⋅ mol−1). The average pressure rate of 85GAP‐Prop burning in a closed bomb reached 7.67 MPa ⋅ s−1 and the maximum instantaneous pressure rate could reach 16.52 MPa ⋅ s−1, significantly higher than the other propellants. The combustion products analysis indicated that the higher GAP content in the GAP‐IPDI energetic thermoplastic polymer more significantly reduced the agglomeration of Al particles and improved the loosening of the combustion products. The rapid combustion gas generation characteristic and energy release of energetic thermoplastic polymer enhanced the combustion characteristics of the fuel‐rich propellant based on Al−Mg, which promoted dispersion level between the metal droplets. This work provides insight into the combustion principles and performance improvements of fuel‐rich propellant based on Al−Mg.

Preparation, quasi-static, and dynamic compressive mechanical properties of BMG-W energetic structural materials

In this paper, the Zr41.2Ti13.8Cu12.5Ni10Be22.5 amorphous alloy powder and the spherical W particles were used to prepare the BMG-xW (BMG=Bulk Metallic Glass, x = 10, 20, 30, 40, 50 vol%) energetic structural materials (ESMs) by spark plasma sintering. The research results on energy performance indicated that the Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy powder had excellent thermal reactivity, high combustion enthalpy and combustion integrity. The microstructure, quasi-static, and dynamic compressive mechanical properties of the BMG-xW ESMs were investigated. The quasi-static compression test showed that when the sintering temperature was 365 °C and above, the BMG-xW ESMs with the W content of 20 vol% to 50 vol% had similar fracture strengths and higher plastic deformation abilities than the BMG samples prepared under the same conditions. We have analyzed the plasticity enhancement mechanism of the BMG-xW ESMs. In addition, the failure modes of the BMG-xW ESMs were all shear fracture, which was conducive to exerting their shear self-sharpening. The Hopkinson compression bar test showed that the fracture strength and failure strain of the BMG-xW ESMs were greater than the Zr41.2Ti13.8Cu12.5Ni10Be22.5 BMG under dynamic compression at the same strain rate, and the higher the W content, the fracture strength and failure strain tended to increase. All samples showed obvious flame during dynamic compression. The larger the strain rate, the lower the W content, the shorter the ignition delay time, the faster the flame spreading speed and the longer the combustion time. The damage experiment confirmed that the BMG-xW ESMs had significantly superior damage performance than the Zr41.2Ti13.8Cu12.5Ni10Be22.5 BMG.