Experimental evaluation of non-lethal projectiles thoracic impacts

On constate depuis une vingtaine d'années une augmentation significative de l'emploi d'armes non-létales, aussi bien au sein des forces de l'ordre que du côté militaire. L'idée est effectivement séduisante: pouvoir stopper ou neutraliser la cible, sans lui occasionner de blessures graves, ou de lésions permanentes, voire létales. La technologie actuellement prépondérante consiste en le tir d'un projectile, généralement très déformable, à l'aide d'un lanceur pneumatique ou d'une arme à feu classique, à des vitesses de l'ordre de 100 m/s. L'impact provoque une douleur, qui amène à la neutralisation ou à l'obtempération de la cible. En pratique, on constate que ces armes provoquent néanmoins des blessures graves et même létales, d'où la nécessité de mettre au point des méthodes d'évaluation avant leur mise sur le marché. Les impacts au niveau du thorax, zone d'impact prépondérante, sont caractérisés par des lésions plus importantes que pour d'autres parties du corps, à l'exception de la tête qui n'est jamais visée. Les lésions observées consistent en des blessures provoquées par un impact non-pénétrant, ou en la pénétration du projectile dans l'organisme. Une étude de la littérature sur le sujet oriente cette recherche vers les résultats obtenus à l'Université de Wayne State, par le professeur C. Bir. Ainsi, le critère lésionnel de l'impact non-pénétrant étudié dans cette thèse sera le (VC)max, même si la méthode mise en place est adaptable à tout autre critère. Par ailleurs, l'étude de la pénétration de la peau s'inspirera d'un modèle anthropomorphique ou "surrogate", également développé par C. Bir. La méthode d'évaluation proposée dans ce travail combine des mesures expérimentales et des simulations numériques. La présente thèse s'intéresse exclusivement à l'aspect expérimental, l'aspect numérique faisant l'objet d'une autre thèse développée au département ABAL (Systèmes d'Armes et Balistique) de l'Ecole Royale Militaire. Les deux tests expérimentaux mis au point consistent en des tirs de projectiles non-létaux respectivement sur une cible supposée infiniment rigide, équipée d'un capteur de force, et sur le "surrogate" susmentionné. Ces deux tests nécessitent l'emploi d'un lanceur pneumatique, développé pour l'occasion, qui permet de tirer l'intégralité des projectiles aux vitesses voulues. Ses caractéristiques inédites apportent entière satisfaction tout au long de l'étude. L'emploi du "surrogate" ne nécessite qu'une mesure de vitesse avant l'impact, tandis que les mesures réalisées lors du tir sur le mur rigide consistent en une mesure de vitesse avant l'impact, ainsi que de force et de déplacement du projectile pendant l'impact. La mesure de force est effectuée à l'aide d'un capteur piézoélectrique, les deux autres sont réalisées à l'aide d'une caméra haute-vitesse. L'emploi de celle-ci nécessite le développement d'un logiciel de poursuite dédié à l'application de mesures dynamiques d'impacts de projectiles non-létaux. Ce logiciel apporte une flexibilité, une précision et quantité d'information jusque là jamais atteintes. Les résultats consistent alors en la prise de ces mesures pour six projectiles commerciaux et un projectile en développement. Un énorme effort est fourni pour quantifier les incertitudes de mesure. celles-ci sont calculées grâce à l'emploi du logiciel de poursuite dédié et constituent une originalité supplémentaire de cette thèse. Finalement l'ensemble des résultats expérimentaux sont collationnés et intégrés dans l'approche hybride expérimentale et numérique pour évaluer le potentiel lésionnel de l'impact non-pénétrant et de l'impact pénétrant, à différentes vitesses d'impact, pour le projectile Spartan LE 40 mm de Nobel Sport et le FN303. Les données obtenues pour ces deux projectiles sont ensuite reliés à des distances de tirs. Trois systèmes d'armes sont alors étudiés: le F2000 pour le projectile 40 mm, et le FN303 et FN303p pour le projectile FN303. Grâce à une étude de dispersion et d'efficacité supplémentaire, les résultats définitifs permettent de dimensionner des distances minimum et maximum d'engagement, qui garantissent un tir sûr et efficace.AR04-AR11 - Evaluation des armes non-létale

Standardisation de l'évaluation de la pénétration à l'impact de projectiles non létaux

Non-lethal weapons are in use in a lot of law-enforcement and military operations. While most of them are kinetic-energy systems, their effectiveness and dangerous limits on human targets are not clearly defined. The assessment of non-lethal projectiles effects on human targets follows usually two main directions: - The evaluation of internal damage - The evaluation of skin penetration This papers focuses on the second point. The literature gives some energy density values for a 50% skin penetration probability when different parts of the human body are shot at. These values are mainly based on cadaver and animals tests conducted in USA. Some countries don’t allow these kinds of tests and it is certainly much more convenient to use a mechanical surrogate for testing purposes. In that case, a standard on which different countries can rely would be a must. Wayne State University proposed in March 2010 a draft proposal for a surrogate to be used as a basis for NATO standardization. This surrogate is based on ballistic gelatin, foam and chamois leather. This paper goal is to assess this future standard surrogate regarding: - The equivalence between cadaver and surrogate penetration results - The reproducibility of the method and its sensitivity to external parameters - The availability and feasibility of basis elements of the surrogate. Our results rely on our own tests in our laboratory, and our views are presented in the final article. We give some recommendations about this standard, based on the statistical analysis of these results and on some practical considerations about the surrogate

Simulation numérique d'impact de projectile non létal sur thorax humain

These last decades have seen the development of a new type of weapons, the non lethal weapons. Unlike the conventional weapons which may cause severe or fatal injuries and whose injury mechanisms are well documented, the non lethal weapons are designed for temporary incapacitation with reversible consequences or minor damage to the human body. They try therefore to fill the gap wherever the use of excessive forces or conventional weapons is not necessary. There are various non lethal technologies but here we will focus on non lethal kinetic energy weapons (NLKEW). The non penetrating characteristics of non lethal projectiles lead to different injury mechanisms to those related to conventional lethal projectiles. In order to better understand these effects and assess the injury severity, experiments are carried out on Post Mortem Human Surrogates (PMHS), animals and mechanical anthropomorphic systems. Nevertheless nowadays with the development of high performance computing systems, numerical simulations based on finite element method are increasingly used because of their cost-effectiveness, their predictive capabilities and their adaptability (for example the possibility of adapting the geometry to take into account various morphologies, …). Physical injury is a consequence of the interaction between the human body and the projectile. To assess the severity of injury, injury criteria are defined. The most used criterion on the assessment of the thorax injury is the maximum viscous criterion. Because of the human body complexity, reliable information on injury mechanisms and tolerance level to the impact of non lethal projectiles is limited. The major challenge in the numerical simulations is the human tissue material model as human tissue responses to impacts are various and complex. As a consequence, models which are biofidelic to the human living tissues are a key issue. To investigate and predict the human thorax response to the impact of the usual non lethal kinetic projectiles (like the FN303, the 40mm COUGAR), a finite element thorax model has been developed from thorax CT-scan images and the projectile FN303 was used. The model was validated by using results (force-time and deflection-time characteristics of the thorax) from experiments on PHMS published in the litterature. Two types of projectiles made of polyvinyl chloride cylinder with 37 mm diameter and respectively 28.5 mm and 100 mm long were used and the human tissue material models were found in open litterature

Calibration dynamique des capteurs Flexiforce pour des mesures balistiques

In the field of terminal ballistics, non-invasive force measurements are sometimes needed. The cheap and thin Flexiforce sensors can be used for this purpose with low collateral effects. This paper works on the development of a method designed to dynamically calibrate the Flexiforce sensor. The objective is to find a calibration parameter that correlates the Flexiforce output signal, in terms of conductance, to the applied force. The process used to achieve this dynamic calibration is based on a drop test. The principle is to impact the sensor with the falling of a specified mass. The force signal delivered by the Flexiforce sensor is afterwards compared to the signal measured by a reference force sensor that measures the same impact. To further validate this measurement, the impact is applied on a spring, placed directly between the falling mass and the Flexiforce. The deflection of that spring is measured with a high-speed camera. Knowing the spring properties, we can determine the force produced by the spring on the two sensors, and consequently validate the reference measurement. The calibration factor seems independent of the applied force, and follows a normal distribution. Both the frequency of the impact and the contact surface have an influence on the output of the Flexiforce sensor. For that reason the calibration process should use a frequency and a contact surface similar to the considered application

Mesures à l'impacts de projectiles non létaux 40mm

In the world of kinetic energy non-lethal weapons (KENLW), the 40mm sponge grenade is a modern projectile that is widely being used. Indeed, it presents different advantages: firstly, thanks to its 40mm diameter, it can be fired with a classic cost-effective grenade launcher. Secondly, its big diameter makes it very unlikely to penetrate the human body, even for impact energy above 100J. Thirdly, it’s a quite accurate projectile for long distance non-lethal impacts, typically between 20m and 50m. These considerations explain why many ammunition manufacturers tend to develop their own 40mm sponge grenade. The 40mm sponge grenade is usually composed of a hard plastic body, with a deformable nose made in foam rubber. The deformation of the nose allows the projectile to absorb energy at impact, making it less lethal for a given velocity than an equivalent stiff projectile. The muzzle velocity is usually between 70m/s and 110m/s, and the mass between 30g and 40g. The muzzle kinetic energy is usually between 120J and 170J. The main issue in the study of this kind of projectiles is its ability to deform at impact. On the one hand, it makes measurements of the impact phenomena more complicated than for a stiff projectile. On the other hand, most of the published studies about KENLW deal with stiff projectiles, and their conclusions may not be applicable for deformable projectiles. Another problem is the wide variety of existing sponge grenades. As the way the projectile deform during the impact can vary from manufacturer to manufacturer, we can expect that the impact phenomena and its induced lethality can also vary, even for the same level of energy. The objective of this study is to assess the impact of different sponge grenades with force sensors and a high-speed camera. The 2 main goals are the following: • Different sponge grenades are shot at different velocities on a stiff surface equipped with a force sensor. The force and deformation occurring during the impact are measured for each projectile and then compared. • A relationship between force and deformation during the impact is established, and then compared at different velocities, for different sponge grenades

Meausrement de la force à l'impact d'un projectile non létal à l'aide d'un capteur Flexiforce

Force measurements are important to experimentally assess the effects of a non- lethal projectile on a human body. In addition they are also necessary to evaluate the bio-fidelity of a system regarding PMHS (post mortem human subject) data. So far, as we can see in the literature, these measurements are usually achieved with an accelerometer placed inside the projectile. By assuming this projectile is perfectly rigid, the impact force can be calculated [1, 2]. However, the limitations are obvious: on the one hand the embedded accelerometer will change the projectile properties. On the other hand the force cannot directly be deduced for the deformable projectiles usually used nowadays. Therefore, a new system to measure impact force has to be developed. In this study, we propose to use the Flexiforce sensor, which is a cheap and very thin force sensor compatible with the expected measurement range [3]. The final objective is to realise an efficient force measurement on any kinetic energy non-lethal weapon (KENLW) projectile, using this particular sensor. We can find in the literature some static calibration [3,4]. As our application is highly dynamical, we started this study with the design and application of a dynamic calibration process. Then results from rigid projectiles (comparing to a classic KENLW projectile) impacting rigid targets (comparing to human body or a biofidelic surrogate) are collected and Flexiforce and accelerometer signals are compared (“rigid-rigid impacts). Finally, force measurements of projectiles impacting deformable surfaces (comparing to the projectile ) with the Flexiforce sensor are achieved (“rigid-soft impacts”)