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  • 权利要求
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    • 专利摘要:
    Method for evaluating aging, remaining life and properties of ballistic protection vests. Bulletproof vests made of polymeric shields modify their properties over time, since they are subjected to conditions of humidity, temperature, light, body heat, among others. This affects the resistance to bullet impact and, therefore, its reliability as a protection system. To know the deterioration over time, aging tests are usually carried out under controlled artificial conditions: but the correlation between natural aging and accelerated aging is a subject of great controversy, so a method that allows reliable information would be desirable. and objective in real time of the state of a protection vest to calculate its reliability and its remaining life in service. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2870305A2
    申请号:ES202031217
    申请日:2020-12-04
    公开日:2021-10-26
    发明作者:Trujillo Francisco Javier Pérez；CARRASCO Mª ISABEL LASANTA；MIGUEL GAMO Mª TERESA DE；Martín Gustavo García；Sánchez Andrea Illana
    申请人:Universidad Complutense de Madrid；
    IPC主号:
    专利说明:

    [0001] Method for evaluating the aging, remaining life and properties of ballistic protection vests
    [0003] TECHNICAL SECTOR
    [0005] The present invention falls within the field of ballistic protection equipment. More specifically, it refers to the prevention of failure of ballistic protection vests due to aging and loss of properties.
    [0007] BACKGROUND OF THE INVENTION
    [0009] Bulletproof vests use layers of tough fiber to capture and deform the bullet, spreading its force over a large surface area of the vest. They can also include layers of metal (such as steel or titanium), ceramic or polyethylene, which provide extra protection to vital areas.
    [0011] The fibers used are Aramid fibers based on Aramid which is a polyamide where at least 85% of the amide bonds are attached to aromatic rings (such as Kevlar® and Nomex®) and UHMWPE fibers, which are polyethylene fabrics that have been improved and now offer a significant reduction in weight and improved ballistic resistance compared to Aramid (such as Dyneema® and Spectra®, for example). Although UHMWPE fibers are younger, Kevlar® is still one of the strongest materials in the world and is still used today for many different purposes.
    [0013] In addition to fibers, vests can include layers of metal (such as steel or titanium), ceramic, and other components (graphene and other carbon compounds, for example) that provide extra protection to vital areas. These additional layers are effective against all pistols and against some rifles.
    [0015] There are several types of regulations referring to bulletproof vests or ballistic plate, the best known being the American NIJ ( National Institute of Justice) regulation, which is accepted worldwide. The NIJ standard provides the level of performance for most bulletproof vests. The NIJ standard specifies which are the minimum requirements for armor that have been tested under its performance protocols, and evaluates and classifies different types of vests according to threat levels.
    [0017] In Europe, the EN ISO 13688: 2013 standard establishes the “General requirements and ballistic protection against stab impacts” and in Spain, the UNE 108132 standard “Opaque shields. Testing and classification of resistance to attack by bullet impacts derived from the firing of firearms (short arms, rifles and shotguns) ”specifies the performance requirements and test methods for the classification of opaque armor resistant to attack by bullet impacts. derived from shooting with firearms. These tests are carried out at a constant temperature of 18 ° C ± 5 ° C.
    [0019] On the other hand, it has been proven that bulletproof vests made of polymeric shields modify their properties in humid environments due to the presence of humidity (not necessarily absorbed) that lubricates the nodes and the fiber wicks and, therefore, reduces the transfer of load between the threads. This does not reduce the resistance of the fibers, but it does reduce the resistance to penetration of the fabric because they offer less resistance to the passage of a projectile.
    [0021] Thus, there are some studies that reflect how a fiber fabric can lose resistance when exposed to humidity and / or temperature conditions, such as the one presented by Chin et al. (J. Chin et al. Polymer Degradation and Stability 92 (2007) 1234-1246) who subjected to humidity conditions of up to 60% and temperature of 60 ° C to bulletproof vests made of PBO, poly (phenylene-2-6 benzobisoxazole ), showing that the fiber loses 30% of its resistance after 84 days of exposure. This deterioration of the properties was attributed to the temperature of the benzoxazole ring, creating functional groups with the subsequent hydrolysis of the amide. Aramids are slightly affected by humidity; It has been reported that, in hot / humid environments, they lose 20% of their mechanical properties (HH Yang. Aramid Fibers. In: Anthony K; Carl Z, editors. Comprehensive Composite Materials, Oxford: Pergamon; (2000) 199-229 ; H. Hansmann, Aramid fibers, Hochschule Wismar Du Pont de Nemours & Company, lnc. (2003) p. 26). However, this effect is more perceptible in aramid composite materials, as demonstrated by the study carried out by Imelinska and Guillaumat (K. lmielinska; L. Guillaumat, The effect of water immersion aging on lowvelocity impact behavior of woven aramid-glass fiber / epoxy composites, Composites Science and Technology. 64 (2004) 2271-2278).
    [0023] For this reason, bulletproof vests on the market, in addition to submitting to the standards demanded by buyers in relation to the level of protection, are also usually required that the fibers that compose it are resistant to cold and heat, and must maintain their properties. in wide temperature ranges (from -30 ° C to 100 ° C, for example) and resistant to humidity. And once purchased, they are usually subjected to confirmatory resistance tests under normal conditions (21 ° C ± 2 ° C), in conditions of low and high temperatures and different degrees of humidity. But also, during subsequent use, personal armor is always exposed to conditions of humidity, temperature, body heat, acid solutions (such as sweat), among others.
    [0025] Therefore, it is necessary to know the behavior that these materials have in humid and temperature environments, not only at the time of purchase (without use) but also to know the possible change in properties that they have as a consequence of their storage or use in function of time, so as to ensure its reliability of protection against ballistic impact.
    [0027] The tests to determine the behavior of the material that make up the vests before the effects of natural factors: temperature, humidity and visible light spectrum, are usually carried out in the laboratory in an accelerated way within chambers under controlled artificial conditions, the main purpose being to establish a relationship between a short period of time at the laboratory level and the behavior of the material under natural conditions.
    [0029] These types of accelerated tests are carried out in special chambers called accelerated aging chambers. These devices are capable of manipulating parameters inside them, such as temperature, the percentage of relative humidity and the wavelength in the irradiated light (the UV spectrum being the most used for these tests). These conditions are applied to material samples under cycles determined by the user based on established standards. In natural aging, however, the material is exposed to real conditions: ambient temperature, visible light spectrum, normal humidity cycles.
    [0030] Achieving this correlation has generated much controversy in the scientific field, since the contrasting conditions that exist with natural and accelerated aging (wavelengths shorter than visible light, temperatures above ambient temperature and relative humidity percentages of up to 100%) make it difficult to establish a correlation with some degree of precision.
    [0032] Many studies have been conducted to correlate accelerated aging and natural aging, such as that conducted by Robert (JH Robert, Durability Testing of Nonmetallic Material, In: 1294 S, ed .: Center For Library Initiatives pursuant to;
    [0033] 1996 ). 13 polymers were studied at the same time by means of mechanical and chemical tests trying to establish a relationship between aging in an aging chamber and their exposure to natural aging. A ratio was reached, in some cases, of 3:24 (three months in accelerated aging represents 24 months of natural aging). In another study (Ricardo Alberto Gamboa Castellanos "Study and characterization of a thermoplastic shielding based on aramid fibers", Doctoral Thesis, 2011 ) accelerated aging tests are carried out by suppressing the UV radiation from the chamber, since it is known that the aramid reduces its resistance by almost 49% after 5 weeks of exposure to visible light (D. Poynter, The Parachute Manual: A Technical Treatise on Aerodynamic Decelerators. For Pub; 4 Rev Sub edition, 1991 , 64), and It is only a question of determining how the humidity absorbed by the composite material affects the impact resistance and, therefore, the ballistic limit of the laminates; in practice, however, the materials can be exposed to light and suffer photo- degradation.
    [0035] For all the above, it would be desirable a method that allows knowing the properties, the degree of degradation and the remaining life of personal protective vests applicable to any base material (ceramic, composite and / or polymeric) with any addition to increase its properties ( graphene, for example) or with any other reinforcement of organic, inorganic or hybrid nature, in such a way that it provides reliable and objective information in real time without the need for extrapolations based on assumptions.
    [0036] EXPLANATION OF THE INVENTION
    [0038] In the present invention a new method for calculating the life is presented remnant of personal protective vests that allows to evaluate the reliability of protection against ballistic impact. The method is based on a calibration curve with respect to the aging of the fibers and composites that compose it. The state of the structural properties, chemical bonding and deterioration are analyzed to be able to evaluate if the personal protective vest may still have remaining in service.
    [0040] The method includes the following stages:
    [0041] - Define a calibration curve for chemical, physical and impact resistance properties of a protection element based on the degree of aging.
    [0042] - Determine the chemical, physical and impact resistance properties of an element of unknown degree of aging.
    [0043] - Locate the value of each property determined in the calibration curve. - Calculate the degree of aging and the remaining life based on the quality standards required to continue in service.
    [0045] The method is applicable to both conventional vests with aramid fibers and new designs that incorporate graphene, new fibers or carbon compounds.
    [0047] As previously indicated, it is not possible to directly correlate simulated aging cycles with the durability of the constituent materials of the personal protective vests since the aging conditions are not common to all vests since, depending on the storage location, degree of humidity, ultraviolet radiation from the light that has hit it, contact with personal sweat, etc., will have a different degree of deterioration.
    [0049] In the present invention it is proposed to carry out aging cycles and, based on them, to reference the aging of materials and the safety limit of durability of the vests. The cycles are carried out until reaching the limit of properties of the vests, when they fail catastrophically when they are pierced by projectiles. A number of cycles are programmed, each with a set duration of days. Vests are removed from time to time and their properties are analyzed. The cycles are prolonged until reaching the point of deterioration-failure in service.
    [0050] Each of the extracted vests is subjected to structural analysis techniques to determine chemical and physical properties that indicate the degree of breakage of the fiber links and the degree of crystallinity, thus determining the degree of structural aging of the materials that make up the vest. . These techniques are:
    [0051] - Fourier transform infrared spectrometry (FTIR), which allows analyzing the breakage of fiber links due to aging. If necessary, additional analysis by RAMAN spectroscopy can also be performed. - Scanning electron microscopy (SEM) that allows knowing the structural integrity.
    [0052] - X-ray diffraction (XRD), for characterization of crystalline phases.
    [0053] - Ballistic impact analysis to determine the critical rejection point.
    [0055] Additional structural characterization techniques can also be employed. Thus, if the vests have ceramic ballistic protection squares, their state of integrity is characterized by radiography in the initial state and in different degrees of ballistic impact.
    [0057] The ballistic impact analysis can be carried out following the quality standard required in each case, for example, according to the UNE108132 standard.
    [0059] In this way, for each of the extracted vests, three structural properties are obtained that characterize their state: the "fingerprint" of the fibers that make up said vests, which allows determining the degree of breakage of the most important links between the fibers, their structural integrity or fracture and their level of ballistic protection Taking into account the moment in which they were extracted, the calibration curve of properties of ballistic protection vests is defined as the variation of these three properties as a function of the simulated aging time.
    [0061] Once the calibration curve (Figure 4) has been obtained, for any vest in different storage conditions, temporary use, time since warranty, etc. you can establish the curve point for each property and estimate its remaining life in service.
    [0062] BRIEF DESCRIPTION OF THE DRAWINGS
    [0063] To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, a set of drawings is attached as an integral part of said description, in which, with an illustrative and non-limiting nature, the following has been represented. following:
    [0065] Fig. 1: represents an example of an aging cycle lasting 7 days, where a relative humidity of 90% is maintained and the temperature is varied between -20 and 55 ° C.
    [0067] Fig. 2: representation of the calibration curve of properties of a vest as a function of simulated aging The red line refers to properties against ballistic impact, the blue line represents the degree of fracture of the fibers and the green line the degree of breakage of fiber bonds.
    [0069] Fig. 3: shows an FTIR spectrum of the fibers that make up a sample vest.
    [0071] Fig. 4: shows a microstructural analysis (SEM) of fibers without deterioration (a) and of deteriorated fibers (b).
    [0073] Fig. 5: location of the value of each property determined in the calibration curve and calculation of the degree of aging and the remaining life.
    [0075] Fig. 6: monitoring by the FTIR technique during the aging of aramid fibers that make up a vest, comparing the absorbance in the spectrum with respect to time.
    [0077] PREFERRED EMBODIMENT OF THE INVENTION
    [0079] The present invention is illustrated by the following examples, which are not intended to be limiting of its scope.
    [0081] Example 1.
    [0082] This example refers to aging cycles of ballistic protection vests.
    [0084] The cycles are established following the French model. Thus, 24 7-day cycles (Figure 1). In each of the cycles, a vest is removed at the end of day 3 and another vest at the end of day 7. If after 24 cycles the deterioration-failure point in service has not been reached, the cycles are prolonged until this point is reached. point.
    [0086] The cycles are carried out under the following conditions:
    [0087] a) Duration: from 7 days onwards until it is old enough so that in ballistic tests the vest is pierced on impact.
    [0088] b) Upper temperature: from 30 to 95 ° C; it can be varied to accelerate aging.
    [0089] c) Lower temperature: from 0 ° C to - 40 ° C, and can also vary to speed up the cycle more or less.
    [0090] d) Degree of humidity: Up to a maximum of 100% humidity, and from 30% humidity, also varying to make the atmosphere more aggressive.
    [0091] e) Chlorides and pollutants in the atmosphere: from 0% to saturation in the liquid solution, to simulate marine, industrial and tropical atmospheres and near the coast.
    [0093] Example 2.
    [0094] This example refers to the FTIR technique used to determine the degree of breakage of the fiber bonds that form the vests.
    [0096] For different aramid vests, using the FTIR technique, a "fingerprint" of the aramid fiber is established (Figure 3). The variation of the intensity of the peaks in the most important bonds is used to determine the degree of breakage of links and the subsequent loss of properties in the face of ballistic impact.
    [0098] A follow-up is also carried out using the FTIR technique to know the evolution of the most critical links of the fiber against aging, observing the variation of the corresponding absorbance peak against time (Figure 5).
    [0100] Example 3
    [0101] The micro-structural state of the fibers that make up the vests is observed using scanning electron microscopy (SEM).
    [0102] Thus, Figure 4 shows the difference between a non-deteriorated aramid fiber (a) and a deteriorated fiber (b).
    权利要求:
    Claims (7)
    [1]
    1. Method for evaluating the degree of aging, remaining life and properties of a ballistic protection element comprising:
    - Define a calibration curve for chemical, physical and impact resistance properties of a protection element based on the degree of aging.
    - Determine the chemical, physical and impact resistance properties of an element of unknown degree of aging.
    - Locate the value of each property determined in the calibration curve.
    - Calculate the degree of aging and the remaining life based on the quality standards required to continue in service.
    [2]
    2. Method, according to claim 1, where the ballistic protection elements are conventional vests composed of aramid fibers or new fibers and which can incorporate new designs such as graphene or carbon compounds.
    [3]
    3. Method, according to claims 1 and 2, where the calibration curve is determined by subjecting the protection element to aging cycles until the vests' property limit is reached, when they fail catastrophically when they are pierced by projectiles, and extracting from time to time elements to analyze their properties.
    [4]
    4. Method, according to claim 3, where the cycles are carried out under the following conditions:
    a) Duration: from 7 days onwards until it is old enough so that in ballistic tests the vest is pierced on impact.
    b) Upper temperature: from 30 to 95 ° C; it can be varied to accelerate aging.
    c) Lower temperature: from 0 ° C to - 40 ° C, which can also be modified to speed up the cycle more or less.
    d) Degree of humidity: Up to a maximum of 100% humidity, and from 30% humidity, varying to make the atmosphere more aggressive.
    e) Chlorides and pollutants in the atmosphere: from 0% to saturation in the liquid solution, to simulate marine, industrial and tropical atmospheres and near the coast.
    [5]
    5. Method, according to claims 2 and 3, where the chemical and physical properties are the degree of breakage of the fiber links and the degree of crystallinity that determine the structural integrity of the materials that make up the vest.
    [6]
    6. Method according to claim 5, where the properties are determined by FTIR analysis, SEM scanning electron microscopy, X-ray diffraction, RAMAN spectroscopy or any other structural characterization technique.
    [7]
    7. Method, according to claims 1 and 2, where the ballistic impact analysis is carried out following the quality standard required in each case.
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    同族专利:
    公开号 | 公开日
    ES2870305R1|2021-11-15|
    引用文献:
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    KR101919304B1|2011-01-18|2018-11-16|데이진 아라미드 비.브이.|Ballistic resistant article comprising a self-crosslinking acrylic resin and/or a crosslinkable acrylic resin and process to manufacture said article|
    JP2015519482A|2012-04-11|2015-07-09|バテル・メモリアル・インスティテュートＢａｔｔｅｌｌｅ Ｍｅｍｏｒｉａｌ Ｉｎｓｔｉｔｕｔｅ|PBO fibers that exhibit improved mechanical properties when exposed to high temperatures and high relative humidity|
    CN109371695B|2018-09-20|2021-05-14|天津工业大学|Preparation method of anti-ultraviolet flexible stab-resistant material|
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    ES202031217A|ES2870305R1|2020-12-04|2020-12-04|Method for evaluating the aging, remaining life and properties of ballistic protection vests|ES202031217A| ES2870305R1|2020-12-04|2020-12-04|Method for evaluating the aging, remaining life and properties of ballistic protection vests|
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