Ballistics Penetration Simulants - lect 23

Ballistic Gels and Animal Analogues

• Ballistic gels help visualize what happens inside the human body during ballistic events.

• They aid in understanding complex phenomena not easily observed with real animal or human tissues.

• Animal analogues are an alternative, with pigs historically considered the closest to human tissues due to biological similarities.

• Live animal trials are not used in modern experimental ballistics.

• If animal models are used, they are typically animals already processed for meat products.

Ballistic Penetration Simulants

• Definition: Any material, biological or synthetic, used to simulate the human body for ballistic penetration testing.

• Examples:

  • Biological animal model systems (used in the past and for specific purposes today).

  • Synthetic gels like those from Clear Ballistics (reusable, remeltable, cost-effective).

• Simulants should provide comparable and reproducible wound data relative to human body penetration by projectiles.

• The goal is similarity, not exact duplication.

Reasons for Using Simulants

• Ethical considerations: Overcoming ethical issues associated with testing on human tissues.

  • Testing on live humans is unethical.

  • Cadaveric tissues are used in some countries under strict conditions (e.g., testing body armor effects).

• Comparative penetration data: Allowing valid comparisons between different projectiles, velocities, energies, stabilities, etc.

• Understanding wounding effects: Gaining insights into the potential wounding effects of projectiles.

• Accurate and reproducible data: Aiming for accuracy, but focusing on reproducibility with synthetic simulants compared to variable biological systems.

• Ballistic gelatin is hyper-elastic, more stretchy than human tissues, leading to more dramatic effects.

• Data reproducibility is crucial for scientific interpretation of results.

Desired Properties of Simulants

• Non-cadaveric (not from human bodies).

• Non-biological if possible.

  • Synthetic gels (polymeric materials) are preferred.

  • Traditional ballistic gel is biological (collagen-based) and degrades, having a short shelf life.

• Ethically sound in all senses.

• Readily available.

• Easy to handle.

• Stable in storage.

• Similar deceleration and deformation behavior upon penetration.

  • Similar depths of penetration.

  • Similar deformations and cavities.

• Similar behavior in relation to transferred kinetic energy.

• Measurable kinetic energy dissipation.

  • Clear materials allow high-speed video analysis.

  • High-speed cameras are expensive (e.g., £300,000).

• Ability to extrapolate temporary cavity diameters.

• Ability to understand and extrapolate the permanent cavity.

• Reproducible results for scientific methods.

• Ability to perform advanced analysis methods (e.g., CT scanning).

  • CT scanners provide three-dimensional images, particularly of bones.

Biological vs. Synthetic Materials

• Biological materials degrade and vary, leading to inconsistencies.

• Synthetic materials offer consistency.

• Mechanical properties of biological systems are difficult to measure due to variability.

• The body's response to trauma is rate-dependent.

  • Punching, stabbing, and shooting result in different body responses due to varying rates of loading.

  • At high rates, the body behaves hydrodynamically, like a lump of water.

• Replicating high rates of trauma while measuring mechanical properties is challenging.

  • It requires complex testing to understand the properties of the body in relation to trauma.

Materials Used to Simulate Soft Tissues

• Water (70% of body, bullet acts as if traveling through water).

• Hydrogels (solid blocks of water using gelatins).

• Wet phone book (not very useful).

• Straw boards (calibrated, but not ideal).

• Clay (moldable, used to measure body armor deformation).

  • Used to create clay bodies for testing body armor.

  • Used for molding necks in head models.

• Transparent gel candles (good for brains due to jelly-like consistency).

• Lead (soft metal, but dense).

• Soaps (glycerin soap can be useful for specific reasons).

• Synthetic polymers (current trend for ballistic blocks).

• Cadavers (ethical issues).

Traditional Ballistic Gelatin

• Collagen-based (from bones and sinews of pigs).

• Two common formulations:

  • 10% ballistic gelatin at 4 degrees Celsius (FBI block).

    • 10% weight percentage in warm water, cooled in a fridge.

    • Requires refrigeration due to temperature sensitivity affecting density.

  • 20% gelatin at 20 degrees Celsius (NATO block).

    • Higher concentration, room temperature.

    • No refrigeration needed.

• The properties of the two blocks should yield similar outcomes.

• NATO block is more universal for various testing conditions.

• This is a recipe (see original document for details) for making ballistic gel blocks.

Soap as a Simulant

• Glycerin soap is a plastic material (not elastic).

• Temporary cavities form but don't collapse, revealing the cavity's shape.

• Provides a way to visualize the temporary cavity without high-speed cameras (more cost effective: \$50 vs \$300,000).

• Was used to understand fragment behavior when high-speed cameras could not be placed near explosions.

Skin Simulants

• Leather (animal hide) can replicate human skin.

• Importance of skin simulation increases as projectile velocity decreases.

• Examples:

  • Upholstery leather.

  • Chamois leather (for thinner skin areas).

• Leather has similar grain structure to real skin due to it being real cured skin.

• Skin variability makes it a less ideal biological simulant since we prefer synethic materials.

Skin Skull Brain Model

• Multi-layered polyurethane bone structure replicates the skull.

• Includes:

  • Hard outer and inner layers (compact bone).

  • Soft, spongy middle layer (Diplo) for flexibility.

• Simplified shape compared to a real head to allow a multi layered structure.

• Supported by a clay neck.

• Silicone skull cap (synthetic skin simulant) with leather fibers to mimic grain structure.

Alternative Head Model

• Uses polyurethane from medical teaching aids (skeletons).

• Simplified (no Diplo layer) for high-velocity trauma simulation.

• Uses ballistic gelatin (10% at 4 degrees Celsius) poured into a skull.

• Uses silicone swimming cap as a skin simulant (cheap alternative).

• Cost-effective ( \$15 vs \$500 for the skin skull-brain model).

Using Head Models

• The models demonstrate bevelling (funnel-shaped opening) at the projectile's exit point in the bone.

• This can give realistic indications of true skulls from cadavers.

Experimental Setup

• Universal receiver (firing block) can accommodate various gun barrels.

• Remote activation for safety.

• Safety measures: eye and ear protection.

• Secure targets.

• Measure projectile velocity using a chronograph or Doppler radar.

Future of Ballistic Simulants

• Increased use of radiography (CT scans) to document wound patterns.

• Validation of current systems by measuring material properties more accurately.

• Potential use of AI and machine learning to better understand body properties and improve simulant materials.

• Laser scanning of crime scenes to enhance analysis.

• Interdisciplinary approach: Using techniques from various fields to improve forensic science.

• Horizon scanning: Identifying and applying innovations from other scientific fields to forensic analysis to improve analysis and accuracy.

Ballistic Gels and Animal Analogues

• Ballistic gels help visualize what happens inside the human body during ballistic events. They provide a translucent medium that mimics the density and viscosity of human tissue, allowing researchers to observe bullet paths, cavity formation, and fragmentation patterns.

• They aid in understanding complex phenomena not easily observed with real animal or human tissues, offering a repeatable and controlled environment for experimentation.

• Animal analogues are an alternative, with pigs historically considered the closest to human tissues due to biological similarities in skin, muscle, and bone density. However, ethical and practical considerations limit their use.

• Live animal trials are not used in modern experimental ballistics due to ethical concerns and regulatory restrictions. Most research now focuses on synthetic simulants.

• If animal models are used, they are typically animals already processed for meat products, minimizing ethical issues by utilizing tissues that would otherwise be discarded.

Ballistic Penetration Simulants

• Definition: Any material, biological or synthetic, used to simulate the human body for ballistic penetration testing. These simulants help researchers understand the effects of projectiles on human tissue without the ethical issues associated with using live subjects or cadavers.

• Examples:

  • Biological animal model systems (used in the past and for specific purposes today). Often, these were employed to study specific physiological responses or tissue interactions that are difficult to replicate with synthetic materials.

  • Synthetic gels like those from Clear Ballistics (reusable, remeltable, cost-effective). These gels offer consistency and can be reused multiple times, reducing waste and cost.

• Simulants should provide comparable and reproducible wound data relative to human body penetration by projectiles. The data should include penetration depth, cavity size, and fragmentation patterns to ensure the simulant accurately represents human tissue response.

• The goal is similarity, not exact duplication. Simulants aim to replicate key characteristics of human tissue to provide meaningful data, rather than creating an exact replica.

Reasons for Using Simulants

• Ethical considerations: Overcoming ethical issues associated with testing on human tissues. This is the primary driver for using simulants, ensuring that research is conducted in a humane and responsible manner.

  • Testing on live humans is unethical and illegal in most jurisdictions.

  • Cadaveric tissues are used in some countries under strict conditions (e.g., testing body armor effects). However, availability and ethical concerns limit their widespread use.

• Comparative penetration data: Allowing valid comparisons between different projectiles, velocities, energies, stabilities, etc. Simulants enable researchers to isolate variables and assess their impact on penetration and wounding.

• Understanding wounding effects: Gaining insights into the potential wounding effects of projectiles. This includes studying temporary and permanent cavity formation, fragmentation patterns, and energy transfer.

• Accurate and reproducible data: Aiming for accuracy, but focusing on reproducibility with synthetic simulants compared to variable biological systems. Reproducibility is crucial for ensuring the reliability and validity of research findings.

• Ballistic gelatin is hyper-elastic, more stretchy than human tissues, leading to more dramatic effects. This can exaggerate the extent of wounding compared to what would occur in human tissue.

• Data reproducibility is crucial for scientific interpretation of results. Consistent data allows researchers to draw meaningful conclusions and make valid comparisons between different scenarios.

Desired Properties of Simulants

• Non-cadaveric (not from human bodies). This eliminates ethical concerns and ensures a consistent supply of material.

• Non-biological if possible.

  • Synthetic gels (polymeric materials) are preferred for their consistency and availability.

  • Traditional ballistic gel is biological (collagen-based) and degrades, having a short shelf life, requiring careful storage and handling.

• Ethically sound in all senses, ensuring that the research is conducted in a responsible and humane manner.

• Readily available to ensure that researchers can easily access the materials needed for their studies.

• Easy to handle, allowing for efficient and straightforward experimental setup.

• Stable in storage to maintain consistent properties over time.

• Similar deceleration and deformation behavior upon penetration.

  • Similar depths of penetration, ensuring that the simulant accurately reflects how projectiles interact with human tissue.

  • Similar deformations and cavities, providing realistic representations of wound trauma.

• Similar behavior in relation to transferred kinetic energy, allowing researchers to accurately assess the energy imparted by a projectile.

• Measurable kinetic energy dissipation. This helps in understanding how energy is transferred and dissipated within the tissue.

  • Clear materials allow high-speed video analysis, providing detailed visual data on projectile behavior and tissue response.

  • High-speed cameras are expensive (e.g., £300,000), but they provide invaluable data on rapid events during ballistic impact.

• Ability to extrapolate temporary cavity diameters, which is crucial for understanding the extent of tissue damage.

• Ability to understand and extrapolate the permanent cavity, which represents the long-term tissue damage caused by the projectile.

• Reproducible results for scientific methods, ensuring the reliability and validity of research findings.

• Ability to perform advanced analysis methods (e.g., CT scanning).

  • CT scanners provide three-dimensional images, particularly of bones, allowing for detailed analysis of fracture patterns and tissue damage.

Biological vs. Synthetic Materials

• Biological materials degrade and vary, leading to inconsistencies in experimental results. This variability can make it difficult to draw meaningful conclusions.

• Synthetic materials offer consistency, ensuring that each experiment is conducted under the same conditions.

• Mechanical properties of biological systems are difficult to measure due to variability in tissue composition and structure.

• The body's response to trauma is rate-dependent. The rate at which force is applied affects how the body responds.

  • Punching, stabbing, and shooting result in different body responses due to varying rates of loading. Each type of trauma introduces force at a different rate, leading to different tissue responses.

  • At high rates, the body behaves hydrodynamically, like a lump of water. This is because the rapid application of force does not allow time for the tissue to deform in a conventional manner.

• Replicating high rates of trauma while measuring mechanical properties is challenging. It requires sophisticated equipment and techniques to accurately capture the body's response.

• It requires complex testing to understand the properties of the body in relation to trauma. This includes using techniques such as high-speed imaging and force measurement to characterize tissue behavior.

Materials Used to Simulate Soft Tissues

• Water (70% of body, bullet acts as if traveling through water). Water's high content in the human body means projectiles interact with it significantly.

• Hydrogels (solid blocks of water using gelatins). These provide a more solid, manageable medium that still retains many of water's properties.

• Wet phone book (not very useful). Although once used, it lacks the consistency and reliability of modern simulants.

• Straw boards (calibrated, but not ideal). These can offer a degree of consistency but do not accurately mimic soft tissue.

• Clay (moldable, used to measure body armor deformation).

  • Used to create clay bodies for testing body armor, providing a measure of how much the armor deforms upon impact.

  • Used for molding necks in head models, offering a way to create realistic head and neck structures for ballistic testing.

• Transparent gel candles (good for brains due to jelly-like consistency). These can mimic the texture and density of brain tissue.

• Lead (soft metal, but dense). While not ideal, it can be used in certain applications due to its malleability.

• Soaps (glycerin soap can be useful for specific reasons). These can be used to visualize temporary cavities formed by projectiles.

• Synthetic polymers (current trend for ballistic blocks). These offer consistency, reusability, and ethical advantages over biological materials.

• Cadavers (ethical issues). While they offer the most realistic simulation, ethical and logistical issues limit their use.

Traditional Ballistic Gelatin

• Collagen-based (from bones and sinews of pigs). This composition gives it properties similar to those of human tissue.

• Two common formulations:

  • 10% ballistic gelatin at 4 degrees Celsius (FBI block).

    • 10% weight percentage in warm water, cooled in a fridge. This formulation is widely used in law enforcement and forensic testing.

    • Requires refrigeration due to temperature sensitivity affecting density. Temperature control is crucial for maintaining consistent results.

  • 20% gelatin at 20 degrees Celsius (NATO block).

    • Higher concentration, room temperature. This formulation is more robust and less sensitive to temperature variations.

    • No refrigeration needed, making it more convenient for certain testing conditions.

• The properties of the two blocks should yield similar outcomes. While the formulations differ, they are designed to produce comparable results.

• NATO block is more universal for various testing conditions due to its stability and ease of use.

• This is a recipe (see original document for details) for making ballistic gel blocks, providing detailed instructions for preparing ballistic gelatin.

Soap as a Simulant

• Glycerin soap is a plastic material (not elastic). This means it deforms permanently rather than springing back to its original shape.

• Temporary cavities form but don't collapse, revealing the cavity's shape. This allows researchers to visualize the extent of the temporary cavity without needing high-speed cameras.

• Provides a way to visualize the temporary cavity without high-speed cameras (more cost effective: $50 vs $300,000). This makes it an accessible tool for researchers with limited budgets.

• Was used to understand fragment behavior when high-speed cameras could not be placed near explosions, providing valuable data in situations where high-speed imaging was not feasible.

Skin Simulants

• Leather (animal hide) can replicate human skin, offering a realistic texture and elasticity.

• Importance of skin simulation increases as projectile velocity decreases. At lower velocities, the skin's properties have a more significant impact on projectile behavior.

• Examples:

  • Upholstery leather, used for general skin simulation.

  • Chamois leather (for thinner skin areas), providing a more accurate representation of thinner skin regions.

• Leather has similar grain structure to real skin due to it being real cured skin, offering a more realistic simulation compared to synthetic alternatives.

• Skin variability makes it a less ideal biological simulant since we prefer synethic materials, synthetic materials offer consistency.

Skin Skull Brain Model

• Multi-layered polyurethane bone structure replicates the skull, providing a realistic representation of the skull's composition.

• Includes:

  • Hard outer and inner layers (compact bone), mimicking the dense outer layers of the skull.

  • Soft, spongy middle layer (Diplo) for flexibility, allowing the model to flex and deform like a real skull.

• Simplified shape compared to a real head to allow a multi layered structure, making it easier to manufacture and analyze.

• Supported by a clay neck, providing support and stability to the model.

• Silicone skull cap (synthetic skin simulant) with leather fibers to mimic grain structure, offering a realistic skin texture and appearance.

Alternative Head Model

• Uses polyurethane from medical teaching aids (skeletons), repurposing readily available materials.

• Simplified (no Diplo layer) for high-velocity trauma simulation, focusing on the key characteristics relevant to high-impact trauma.

• Uses ballistic gelatin (10% at 4 degrees Celsius) poured into a skull, providing a realistic representation of brain tissue.

• Uses silicone swimming cap as a skin simulant (cheap alternative), offering a cost-effective way to simulate skin.

• Cost-effective ($15 vs $500 for the skin skull-brain model), making it accessible for researchers with limited budgets.

Using Head Models

• The models demonstrate bevelling (funnel-shaped opening) at the projectile's exit point in the bone. This is a key indicator of the direction of the projectile.

• This can give realistic indications of true skulls from cadavers, offering valuable insights for forensic analysis.

Experimental Setup

• Universal receiver (firing block) can accommodate various gun barrels, allowing for testing with different firearms.

• Remote activation for safety, ensuring that the experiment can be conducted from a safe distance.

• Safety measures: eye and ear protection, crucial for protecting researchers from potential hazards.

• Secure targets to ensure consistent and accurate results.

• Measure projectile velocity using a chronograph or Doppler radar, providing critical data on projectile performance.

Future of Ballistic Simulants

• Increased use of radiography (CT scans) to document wound patterns, providing detailed three-dimensional images of tissue damage.

• Validation of current systems by measuring material properties more accurately, improving the reliability and accuracy of simulants.

• Potential use of AI and machine learning to better understand body properties and improve simulant materials, using advanced algorithms to analyze complex data and identify new materials.

• Laser scanning of crime scenes to enhance analysis, providing detailed three-dimensional maps of the scene.

• Interdisciplinary approach: Using techniques from various fields to improve forensic science, bringing together expertise from different disciplines to advance the field.

• Horizon scanning: Identifying and applying innovations from other scientific fields to forensic analysis to improve analysis and accuracy,