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Brisance (/brɪˈzɑːns/, /ˈbriːzəns/, /ˈbriːzɒns/; from French briser 'break, shatter'[1]) is the shattering capability of a high explosive, determined mainly by its detonation pressure.

Application

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Brisance is of practical importance in explosives engineering for determining the effectiveness of an explosion in blasting and quarrying, and in weaponry such as fragmenting shells, bomb casings, grenades, and plastic explosives. The sand crush test[2] and Trauzl lead block test are commonly used to determine the relative brisance in comparison to TNT (which is considered a standard reference for many purposes).

The value of brisance depends on the application. At one extreme, if an explosive is to be used for propulsion, e.g. by driving a piston or a bullet, brisance is likely to be undesirable, because the objective will be to move the load, not to shatter it or the engine or firearm, nor to produce a loud report. Such propulsive charges are designed to burn controllably, such as carburetted fuel/air mixes in vehicle piston engines, or nitrocellulose fibres or grains of controlled textures in firearm cartridges.

For certain types of blasting, as in some civil engineering works, the objective is to loosen the undesired material with the least amount of explosion and expense, both in explosive and safety precautions. Similarly, in quarrying a product such as slate, in which the objective is to loosen it from surrounding rock with as little damage as possible, no more brisance than is necessary to split off the valuable product profitably, without unacceptable waste, is desired. For this purpose blasting powder of low brisance is necessary.[3]

In shattering hard rock or military defences, high brisance generally is necessary, so high explosives with extremely high detonation velocity are used as far as is practical. One of the most brisant of the conventional explosives is cyclotrimethylene trinitramine (also known as RDX or Hexogen).[4] RDX is the explosive agent in the plastic explosive commonly known as C-4, constituting 91% RDX by mass.[5]

Fragmentation occurs by the action of the transmitted shock wave, the strength of which depends on the detonation pressure of the explosive. Generally, the higher this pressure, the finer the fragments generated. High detonation pressure correlates with high detonation velocity, the speed at which the detonation wave propagates through the explosive, but not necessarily with the explosive's total energy (or work capacity), some of which may be released after passage of the detonation wave. A more brisant explosive, therefore, projects smaller fragments but not necessarily at a higher velocity than a less brisant one.

See also

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References

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Brisance

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Brisance is the shattering or crushing effect produced by the detonation of an explosive, particularly high explosives, and is characterized by the material's ability to fragment or deform nearby objects through rapid pressure buildup.[1] It is primarily determined by the detonation velocity and pressure of the explosive, with higher values indicating greater disruptive power compared to the overall energy release.[2] The term originates from the French word brisant, the present participle of briser meaning "to break," derived from Old French brisier and ultimately of Celtic origin, reflecting its association with breakage and fragmentation.[2] First appearing in English in the early 20th century in discussions of explosives engineering, brisance distinguishes high explosives—which detonate at supersonic speeds exceeding 1,000 m/s—from low explosives that deflagrate more slowly.[3][4] Brisance is quantified through standardized tests and is crucial in applications requiring localized fragmentation, such as mining, demolition, and munitions.

Fundamentals

Definition

Brisance is the shattering or fragmenting capability of an explosive, characterized by its ability to break apart or deform surrounding materials through the rapid buildup of pressure during detonation.[5] This property arises from the explosive's capacity to generate a high-pressure shockwave that delivers energy intensely and locally, distinguishing it as a key trait of high explosives.[6] Unlike overall explosive power, which measures the total energy released—often assessed by heat of explosion or total gas production—brisance specifically quantifies the localized destructive effect on a target, emphasizing fragmentation over broad propulsion or heave.[5] High brisance thus prioritizes the speed and intensity of the pressure pulse, enabling efficient material breakup in applications like demolition or munitions.[6] Representative examples include high-brisance explosives such as pentaerythritol tetranitrate (PETN), with a detonation velocity around 6200–8000 m/s, and cyclotrimethylenetrinitramine (RDX), reaching up to 8500 m/s, both known for their strong fragmenting action.[6] In contrast, low-brisance materials like black powder exhibit minimal shattering due to their deflagration rather than detonation, producing a slower pressure rise with limited fragmentation capability.[6] Brisance correlates qualitatively with detonation velocity, where higher velocities enhance the shattering effect.[5]

Etymology and Historical Development

The term "brisance" derives from the French verb briser, meaning "to break" or "shatter," reflecting its focus on the rapid fragmenting action of an explosion. This etymological root traces back to Old French brisier, of Celtic origin, and entered English usage in the early 20th century to describe a specific property of high explosives.[2][7] The concept of brisance emerged in the late 19th century amid rapid advancements in explosive chemistry, particularly with the study of nitroglycerin and Alfred Nobel's dynamite, which required distinguishing the localized shattering effect from broader explosive energy release. French chemist Paul Vieille played a pivotal role in this development through his 1880s research on smokeless powders and detonation phenomena, collaborating with Marcellin Berthelot to measure detonation velocities that underscored brisance as a distinct metric. This period marked the term's first formal applications in scientific literature, formalizing its use to evaluate high explosives beyond simple power output.[6] Following its introduction in post-1870s ballistic testing, brisance became integral to explosive assessment, with early methods like lead block expansions quantifying the shattering capability of materials such as nitroglycerin-based dynamites. By World War I, the term was central to military evaluations, guiding the selection of high-brisance fillers like TNT for artillery shells to maximize fragmentation and penetration effects in combat.[6]

Physical Principles

Relation to Detonation Velocity and Pressure

Brisance in explosives is primarily determined by the peak detonation pressure PP and the detonation velocity DD, with high values of DD—typically exceeding 6000 m/s—generating intense shock waves that enhance the shattering and fragmentation of surrounding materials.[8][9] A key relationship linking these parameters is the approximate equation for detonation pressure:
P≈ρD24, P \approx \frac{\rho D^2}{4},
where ρ\rho is the density of the explosive. This formulation demonstrates the quadratic dependence of pressure on detonation velocity, underscoring how rapid detonation rates amplify the localized forces responsible for brisance.[10] The underlying physics involves supersonic shock wave propagation through the explosive and into adjacent materials, where the wave induces adiabatic compression ahead of the reaction zone. This compression rapidly elevates temperature and pressure, initiating a self-sustaining detonation while transmitting high-amplitude stresses into the target material.[11] The resulting shock waves cause material fragmentation by generating tensile stresses that exceed the target's fracture strength, leading to brittle failure and pulverization; for instance, the steep pressure gradient from high-DD detonations promotes spallation and fine particle breakup through localized adiabatic heating and shear.[11][12]

Distinction from Explosive Power

Brisance refers to the rapid, localized shattering effect produced by an explosive during detonation, primarily driven by the rate of pressure buildup rather than the total energy output. This rate-dependent property arises from the explosive's ability to generate a high detonation pressure in a short time, enabling it to fragment surrounding materials effectively. In contrast, explosive power, often termed strength, measures the overall energy release, quantified through metrics like heat of explosion and gas volume, which determine the capacity to perform work such as displacing or heaving large volumes of material. While brisance emphasizes the speed and intensity of the initial shock wave, explosive power focuses on sustained energy delivery over time, making the two distinct despite occasional overlap in high-performance explosives.[13] A clear illustration of this distinction appears in ammonium nitrate-based explosives, which exhibit high explosive power due to substantial heat of explosion and gas production but low brisance owing to their relatively slower detonation velocities, typically below 5000 m/s. This results in effective heaving for applications like quarrying but poor fragmentation. Conversely, nitroglycerin demonstrates both high brisance, from its rapid pressure rise and detonation velocity around 7300 m/s, and substantial power, allowing it to shatter targets while also delivering significant overall energy. These examples highlight how brisance is not synonymous with total energy content, as slower-reacting oxidizers like ammonium nitrate prioritize volume expansion over instantaneous disruption.[14][13] Conceptually, brisance prioritizes fragmentation and targeted destruction by exploiting the explosive's density and detonation rate to maximize localized stress, whereas explosive power supports broader displacement through cumulative gas pressure and thermal output. High brisance is thus essential for scenarios requiring precise breakup of structures, as it concentrates force to overcome material cohesion quickly, unlike power-driven effects that may merely push material aside without breaking it apart. This framework underscores brisance's role in applications demanding efficiency in shattering over mere bulk movement.[13]

Measurement

Traditional Test Methods

Traditional test methods for assessing brisance emerged in the early 20th century as empirical approaches to quantify the shattering effect of explosives through observable physical deformations or disruptions. These methods relied on simple setups to compare relative brisance among materials, often using standard reference explosives like TNT for calibration. They were pivotal in ordnance and mining research, providing practical insights before advanced instrumentation became available.[15][16] The sand crush test, one of the earliest standardized methods, involves detonating a small charge within a column or chamber of calibrated sand to measure the volume or weight of material crushed, with greater disruption indicating higher brisance. In the procedure developed by W.O. Snelling and refined by C.G. Storm and W.C. Cope at the U.S. Bureau of Mines, a 0.400 g sample of the explosive is initiated in a setup containing 80.0 ± 0.1 g of standardized sand (20-30 mesh size), typically confined in a tube or chamber; the sand is then sifted through a No. 30 sieve, and the weight of the fines passing through is averaged over five trials to determine the crushing efficiency.[15] A variant for larger charges uses 1000 g of Ottawa sand (passing No. 30 sieve) with a 0.400 g charge, focusing on the total volume displaced or crushed to assess shattering power.[15] This test, devised around 1910 and detailed in U.S. Bureau of Mines Technical Paper 125 (1916), offered a straightforward way to evaluate brisance relative to TNT, where typical results show TNT crushing about 43-48 g of sand under comparable conditions.[15] Its historical significance lies in enabling early comparative studies of high explosives in mining and military applications, influencing safety protocols and material selection during World War I-era developments.[16] The lead block test, commonly known as the Hess test, measures brisance by the compressive deformation of a soft lead cylinder subjected to the shock wave from a detonating charge, with deeper compression signifying greater shattering capability. In the standard setup, a 50 g cylindrical charge (40 mm diameter) of the explosive is placed atop a 10-30 mm thick steel disc, which rests on a lead cylinder (40 mm diameter, 60 mm height) mounted on a massive steel base; the charge is initiated with a detonator such as 0.65 g PETN, and the reduction in the lead cylinder's height—measured at four points and averaged—is recorded as the brisance value in millimeters.[17] For highly brisant materials, the charge may be reduced to 25 g to avoid excessive deformation.[17] Originating in Austria and attributed to Hess in the early 1900s, the method was refined by researchers like Wöhler and Matter in 1907 and adapted by the Prussian Military Research Department with a steel piston and nickel steel plate for enhanced precision in ordnance testing.[16] By the 1910s, it had become a cornerstone of German military explosive evaluation, as seen in comparative studies of materials like picric acid and TNT, where results often showed compressions of 15-20 mm for standard high explosives.[16] This test's enduring impact stems from its simplicity and correlation with detonation pressures, facilitating rapid assessments in early 20th-century research despite limitations in quantitative accuracy compared to later methods.[17]

Quantitative Metrics and Units

Brisance is quantified through empirical metrics that emphasize an explosive's ability to generate rapid pressure and induce fragmentation, often benchmarked against trinitrotoluene (TNT) as the standard reference material. Relative brisance values are commonly expressed as percentages of TNT's performance in standardized tests, such as the sand crush test, where a small charge (typically 0.1-0.4 g) is detonated within a bed of graded sand (e.g., 30-mesh size), and the mass of pulverized sand is measured. In this test, TNT crushes approximately 48 g of sand, serving as the 100% baseline. For example, pentaerythritol tetranitrate (PETN) achieves 62.7 g (131% relative to TNT), while cyclotrimethylenetrinitramine (RDX) yields 60.2 g (125% relative to TNT). These values highlight how high-velocity explosives like PETN exhibit greater shattering power due to their enhanced pressure profiles.[4] Units for brisance measurement are predominantly non-SI and test-specific, reflecting practical assessments of compression or fragmentation rather than absolute thermodynamic quantities. The sand crush test uses grams (g) of pulverized material to quantify disruptive capacity, while lead block compression tests (e.g., Hess method) report deformation in millimeters (mm) or, less commonly, derived volume reduction in cubic centimeters (cm³) for the crushed cylinder. Fragmentation-based metrics, such as fragment count from arena tests, enumerate the number of pieces generated from a standardized target (e.g., steel plate or rock sample), providing a direct indicator of shattering efficiency; higher counts correlate with increased brisance. In modern contexts, brisance is increasingly equated to peak detonation pressure in gigapascals (GPa), bridging empirical tests to hydrodynamic models.[18][19] Correlations to other explosive properties enable scaled predictions of brisance, with detonation velocity (D, in m/s) serving as a key proxy due to its influence on pressure buildup. An empirical brisance index can be approximated as (D / 1000)^2, yielding a dimensionless scaling factor relative to TNT (where D ≈ 6900 m/s gives an index of ≈47.6); for PETN (D ≈ 8000 m/s), this yields ≈64, or roughly 134% of TNT, aligning closely with sand test results. More precise models incorporate density (ρ, in g/cm³) and the adiabatic index (γ ≈ 3 for ideal gases), such as the impulse pressure formula $ p_i = \frac{\rho D^2}{\gamma} $ (in GPa), which estimates the effective pressure driving fragmentation—for TNT at ρ = 1.637 g/cm³, this approximates 20-25 GPa. These metrics prioritize conceptual scaling over exhaustive tabulation, ensuring brisance evaluations inform applications like munitions design without over-relying on variable test conditions.[19][4]

Influencing Factors

Chemical Composition

The brisance of an explosive is significantly influenced by its chemical composition, particularly the presence of high-nitrogen compounds such as azides and nitrates, which facilitate rapid decomposition into stable nitrogen gas, generating high pressures during detonation.[20] These compounds release substantial energy through the formation of N≡N triple bonds, promoting a self-contained reaction that accelerates the detonation front and enhances shattering power.[21] For instance, azides like lead azide decompose exothermically to produce nitrogen gas bubbles that amplify shock waves, while nitrates such as those in ammonium nitrate provide both nitrogen and oxygen for efficient oxidation, contributing to elevated detonation pressures.[20] A prime example of high brisance arises from cyclotrimethylenetrinitramine (RDX), where the molecule's strained heterocyclic ring structure, combined with three nitro groups, enables rapid ring-opening and decomposition, yielding a detonation velocity of approximately 8.75 km/s and high pressure that maximizes fragmentation.[22] In contrast, black powder, composed primarily of potassium nitrate, charcoal, and sulfur, exhibits low brisance because it undergoes deflagration—a subsonic combustion process—rather than detonation, resulting in slower energy release and minimal shattering effect.[4] In emulsion explosives, sensitizers play a key role in boosting brisance by creating inhomogeneities that initiate and sustain detonation. Aluminum powder acts as a solid sensitizer, generating localized hot spots upon shock compression to increase detonation velocity and pressure, as demonstrated in formulations where it enhances performance alongside microballoons.[23] Similarly, peroxides such as hydrogen peroxide decompose to form gas microbubbles, lowering the activation energy for detonation and improving brisance in water-resistant emulsions by facilitating faster energy propagation.[23]

Physical Properties of Explosives

The density of an explosive material significantly influences its brisance, as higher density leads to increased detonation pressure and velocity of detonation (VOD), thereby enhancing the shattering effect. According to the Chapman-Jouguet theory, detonation pressure $ P $ is proportional to the product of density $ \rho $ and the square of VOD $ D $, expressed as $ P \propto \rho D^2 $. For instance, cyclotrimethylenetrinitramine (RDX) exhibits a VOD of 8639 m/s and detonation pressure of 347 kbar at a density of 1.80 g/cm³, compared to 8035 m/s and lower pressure at 1.60 g/cm³. Pressed explosives achieve higher densities than loose powders, resulting in greater brisance; ammonium nitrate-fuel oil (ANFO) at 0.884 kg/dm³ shows a detonation pressure of 6.28 GPa and brisance dent depth of 10.94 mm, outperforming lower-density variants. Confinement, such as tamping in blast holes, enhances brisance by sustaining the shock wave and increasing VOD and pressure. In ANFO explosives, greater wall thickness in confining tubes (e.g., steel at 10.3 mm) raises VOD to 3.46 km/s and dent depth to 20.0 mm, compared to 2.19 km/s and 7.6 mm at 2.8 mm thickness. Grain size also modulates brisance, with finer particles promoting higher packing density and faster energy release, accelerating detonation initiation and propagation. Smaller grains in high explosives like RDX improve shock sensitivity and overall brisance by reducing the reaction zone duration. Temperature and humidity affect brisance through their impact on reaction rates and material integrity. Elevated temperatures can lower the critical detonation threshold, potentially increasing performance up to stability limits, as seen in pentaerythritol tetranitrate (PETN) with a critical temperature of 192°C. High humidity reduces brisance in hygroscopic explosives by moisture absorption, which desensitizes the material and slows detonation; RDX, for example, absorbs 0.12% moisture at 25°C and 100% relative humidity, leading to diminished VOD and pressure in wet conditions.

Applications

Military and Demolition Uses

In military applications, high-brisance explosives are essential for munitions designed to maximize fragmentation of the casing, thereby enhancing lethality against personnel and light structures. Composition B, a mixture of approximately 60% RDX (cyclotrimethylenetrinitramine) and 40% TNT with 1% wax, exemplifies this role due to its brisance of 113-142% relative to TNT, which promotes rapid shattering of artillery shell casings into numerous high-velocity fragments.[5] For instance, in 90 mm high-explosive shells, Composition B generates up to 998 fragments, significantly increasing the anti-personnel radius compared to lower-brisance fillers like TNT alone.[5] This property stems from RDX's high detonation velocity of 8,100-9,110 m/s, enabling efficient energy transfer to the casing for controlled fragmentation rather than mere blast displacement.[4] In demolition operations, brisance is critical for shaped charges that require precise, localized shattering to breach metal structures, such as armored vehicles or fortifications, while minimizing unwanted heave or scatter. PETN (pentaerythritol tetranitrate), with a brisance of 129-141% relative to TNT and a detonation velocity up to 8,300 m/s, is commonly employed in these configurations, often in pentolite (50/50 PETN/TNT) formulations.[5][4] Its rapid pressure buildup ensures a focused jet formation in shaped charges, capable of penetrating up to 76 mm of armor at optimal standoff distances of 2-6 charge diameters, ideal for tactical breaching without excessive collateral disruption.[5] This precision distinguishes high-brisance materials from bulk explosives, allowing engineers to achieve structural failure through shattering rather than broad displacement. During World War II, the prioritization of brisance in bomb design amplified anti-personnel effects in fragmentation munitions, where rapid casing breakup was key to dispersing lethal projectiles over wide areas. Composition B filled about 40% of U.S. general-purpose bombs, enhancing fragment production for infantry suppression.[5] Similarly, pentolite-based charges in bazooka rockets, rifle grenades, and demolition kits leveraged PETN's superior shattering capability to target exposed troops, contributing to the era's shift toward high-velocity fragment munitions over pure blast weapons.[5] These applications underscored brisance's role in optimizing explosive efficiency for defensive and offensive scenarios.

Mining and Civil Engineering

In mining and civil engineering applications, brisance is optimized to facilitate controlled rock fragmentation during non-military blasting, prioritizing uniform breakage for efficient material handling while avoiding excessive damage to surrounding structures. Emulsion explosives, including variants like ammonium nitrate fuel oil (ANFO), are widely used in quarry blasting due to their tunable brisance, which allows for precise energy release to achieve consistent fragment sizes without over-crushing the rock. This approach minimizes secondary breakage costs and enhances downstream processing, as ANFO's moderate brisance—typically corresponding to detonation velocities of 3,200–4,500 m/s—promotes effective shearing in softer to medium-hard formations like limestone.[24] In contrast, higher-brisance emulsions, such as those from commercial formulations like TITAN, deliver velocities up to 6,000 m/s for denser rock types, ensuring better penetration and fragmentation uniformity in aggregate production.[25] For tunnel and road construction, low-to-medium brisance explosive mixes are preferred to induce rock heave—lifting and displacing material—while reducing flyrock hazards that could endanger personnel and infrastructure. These mixes, often emulsions with reduced sensitizers, generate sufficient shattering power for excavation without excessive projection of debris, as seen in smooth wall blasting techniques where alternate boreholes use low-strength charges to control overbreak and maintain tunnel stability. Brisance levels are adjusted via composition to align with rock properties, minimizing airblast and ground vibrations in urban or sensitive environments.[26][24] Such controlled application ensures precise contouring, as excessive brisance could lead to uncontrolled fracturing and increased flyrock trajectories beyond safety perimeters.[27] Recent developments in the 2020s have introduced high-brisance emulsion explosives enhanced with additives like sodium borohydride (NaBH₄) to improve performance in hard rock mining and civil projects. These formulations increase detonation velocity and pressure, with optimal NaBH₄ content of 5% boosting brisance by up to 66.5% compared to standard emulsions, resulting in finer fragmentation and higher energy efficiency in challenging lithologies. This innovation addresses limitations in traditional mixes for deep quarries or tough terrains, reducing blast rounds and operational costs while maintaining safety standards.[28]

References

  1. Brisance | NIST - National Institute of Standards and Technology
  2. BRISANCE Definition & Meaning - Merriam-Webster
  3. brisance, n. meanings, etymology and more | Oxford English ...
  4. Properties of Selected High Explosives - PacSci EMC
  5. Results of brisance using the Hess method - ResearchGate
  6. Prediction of the Brisance of Energetic Materials - Wiley Online Library
  7. [PDF] 9546041.pdf - Environmental Protection Agency (EPA)
  8. None
  9. BRISANCE definition in American English - Collins Dictionary
  10. Brisance – Knowledge and References - Taylor & Francis
  11. [PDF] TNT Equivalence - OSTI.GOV
  12. US20160161236A1 - Device for the controlled initiation of the ...
  13. A Preliminary Study on the Design Method for Large-Diameter Deep ...
  14. None
  15. (PDF) Effects of heat-treatment and explosive brisance on ...
  16. [PDF] explosives-6th-edition-by-meyer-kohler-and-homburg-2007.pdf
  17. Detonation Performance of Aluminum-Ammonium Nitrate Explosives
  18. [PDF] ENCYCLOPEDIA OF EXPLOSIVES AND RELATED ITEMS ... - DTIC
  19. [PDF] Explosives, Volume 2, Properties and Tests - Bulletpicker
  20. [PDF] Lead block compression test for determining the brisance of ...
  21. [PDF] Encyclopedia of Explosives and Related Items. Volume 5 - DTIC
  22. [PDF] Determining the brisance of selected emulsion explosives used in ...
  23. The Explosive Chemistry of Nitrogen | Resonance
  24. [PDF] Progress in High-Nitrogen Chemistry in Explosives, Propellants and ...
  25. [PDF] molecular modelling of some explosives and propellants
  26. A Comprehensive Review of the Influence of Sensitizers on ... - MDPI
  27. [PDF] Engineering Geology Field Manual - Volume II - 2nd Ed. - Chapter 19
  28. Metal Bulk Explosives | Dyno Nobel
  29. [PDF] Tunneling in Rock by Drilling and Blasting - rexresearch1
  30. [PDF] Engineering and Design Blasting For Rock Excavations
  31. Research on the development and performance of new high ...
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