SOLID PROJECTILE WITHOUT STABILIZING STRUCTURE FOR BIRD STRIKE TESTS CONSISTING OF A GEL COMPRISING GLYCEROL

Abstract

Disclosed are a projectile and a method of its manufacture for the field of investigating the strength properties of a solid material by application of a mechanical force and more particularly for bird strike tests consisting of a gel including glycerol. A projectile 1 according to the invention may have a central portion 4 of cylindrical shape including a substantially hemispherical portion 2, 3 at each of the ends thereof.

Claims

1-10. (canceled)

11. A solid projectile without stabilizing structure for bird strike tests, wherein the projectile comprises more than 20% of glycerol.

12. The projectile according to claim 11, wherein the projectile comprises between 30% and 40% of glycerol.

13. The projectile according to claim 11, wherein the projectile comprises a gelling agent, glycerol, microbeads and water.

14. The projectile according to claim 13, wherein the microbeads have a size lower than 200 μm.

15. The projectile according to claim 13, wherein the microbeads are made of phenolic resin.

16. The projectile according to claim 13, wherein the projectile comprises: 2% to 8% of the gelling agent, 30% to 40% of glycerol, 1% to 5% of microbeads, at least 47% of water.

17. The projectile according to claim 16, wherein the projectile comprises 5% of the gelling agent.

18. The projectile according to claim 16, wherein the projectile comprises 35% of glycerol.

19. The projectile according to claim 16, wherein the projectile comprises 3.2% of microbeads.

20. The projectile according to claim 16, wherein the projectile comprises 56.8% of water.

21. The projectile according to claim 13, wherein the gelling agent is selected from the following list: gelatin, agar, carrageenan, pectin, konnyaku, carob gum, alginates, gellan gum, hypromellose, hydroxypropylmethyl cellulose, xantham gum and starch.

22. The projectile according to claim 11, wherein the projectile has a hemispherical shape on either side of a cylindrical central portion.

23. The projectile according to claim 22, wherein the central portion has a diameter between 90 mm and 130 mm for a height between 60 mm and 100 mm.

24. The projectile according to claim 23, wherein the central portion has a height of 70.1 mm and a diameter of 95 mm.

25. The projectile according to claim 23, wherein the central portion has a height of 88.3 mm and a diameter of 119.7 mm.

26. The projectile according to claim 11, wherein the projectile has a density between 950 kg/m.sup.3 and 970 kg/m.sup.3.

27. A method for manufacturing a projectile according to claim 13, wherein the method comprises the following successive steps: mixing the gelling agent in the glycerol for providing a binding, mixing the microbeads with the binding, adding hot water under stirring for several minutes, the water having been previously heated at a temperature between 80° C. and 85° C., pouring the resulting mixture into a mold having the desired shape of the projectile.

28. The method according to claim 27, wherein the step of pouring the resulting mixture into a mold having the desired shape is performed when the temperature of the mixture is between 50° C. and 54° C.

Description

[0030] Other advantages and features will become more apparent upon reading the description of several embodiments of the invention, together with the appended drawings in which:

[0031] FIG. 1 shows an example for the shape of a solid projectile without stabilizing structure according to the invention,

[0032] FIG. 2 shows the type of pressures measured on a plate as a function of time, the curve No. 1 being for the chicken and the curve No. 2 being for the impactor (AM) according to the invention,

[0033] FIG. 3 shows an example of view, under a microscope, of the microbeads within a projectile according to the invention,

[0034] FIG. 2 shows a table regrouping calculations of: [0035] the average of the correlation coefficients obtained on the various sensors, [0036] the average of the amplitude ratios obtained on the various sensors, [0037] the ratio of the kinetic energies of the chicken and the impactor (AM),

[0038] wherein the calculations have been performed from measurements of pressure and of deformation of said plate.

[0039] FIG. 1 shows an example for the shape of a solid projectile 1 without stabilizing structure according to the invention. It has a central portion 4 of cylindrical shape comprising a substantially hemispherical portion 2, 3 at each of its ends. The height of the central portion 4 is about 70.1 mm and its diameter is equal to about 95 mm, thereby having a maximum length of about 165.1 mm for a mass of about 908 g.

[0040] This projectile is composed of: [0041] 5% of gelling agent, namely agar with high solubility, [0042] 35% of glycerol, [0043] 3.2% of microbeads, [0044] 56.8% of water.

[0045] The preparation thereof was as follows 1:

[0046] 1. Heating water at a temperature between 80° C. and 85° C.,

[0047] 2. Mixing the gelling agent, namely agar, in the glycerol for obtaining a binding,

[0048] 3. Mixing the microbeads with the binding,

[0049] 4. Adding hot water smoothly and under stirring for several minutes, for example 5 minutes,

[0050] 5. Cooling the resulting mixture to a temperature between 50° C. and 54° C., and then pouring the resulting mixture into a mold having the shape of the projectile,

[0051] 6. Cooling at ambient temperature.

[0052] After complete cooling, the resulting projectile is unmolded and then stored, for example under plastic film, at a temperature preferably between 5° C. and 10° C.

[0053] Tests for comparison between the consequences of a chicken strike and that of an impactor (AM) according to the invention have been performed with a test piece constituted by a Kevlar plate on the rear face of which have been arranged pressure sensors FX, FY, FZ and strain gauges.

[0054] As shown in Table 1, first tests 2 and 17 were intended to describe the consequences of a strike of a chicken of 925 g and of an impactor according to the invention of 900 g which were thrown against the front face of said plate with an angle of 45° at a speed of 117 m/sec, respectively 123 m/sec, and second tests 2bis and 17bis were intended to describe the consequences of a strike of a chicken of 905 g and of an impactor according to the invention of 900 g which were thrown against the front face of said plate with an angle of 45° at a speed of 165 m/sec, respectively 167 m/sec.

TABLE-US-00001 TABLE 1 Plate Firing Speed Mass Energy Target Angle Projectile No. No. (m/sec) (g) (J) Kevlar 45 Substitute 678 2 123 900 6808 Chicken 679 17  117 925 6331 Substitute 678  2 bis 167 900 12550 Chicken 679 17 bis 165 905 12319

[0055] The pressures applied on said plate, measured as a function of time, are the same type as those shown in FIG. 2, the curve No.1 being for the chicken and the curve No.2 being for the impactor (AM) according to the invention. It can be noted that an offset of the pressure peaks increases over time.

[0056] Also, the comparison between the general shape of both curves is performed by calculating, as a function of time, the correlation coefficient of both curves between the initial time and time t. This coefficient is between −1 and 1; it is equal to 1 when these curves vary exactly in phase, and is equal to −1 if they are in antiphase. Furthermore, for quantifying the similarity of the importance of the deformations applied, it is necessary to calculate the amplitude ratio, namely the ratio of the efficient values of the signals.

[0057] From these results, have been calculated: [0058] the average of the correlation coefficients obtained on the various sensors, [0059] the average of the amplitude ratios obtained on the various sensors, [0060] the ratio of the kinetic energies of the chicken and of the impactor (AM)

[0061] Table 2 provides the results of the calculations mentioned above.

TABLE-US-00002 TABLE 2 Test parameters Energy Average of amplitude Speed Average of correlations Chicken/AM ratios Chicken AM Angle (m/sec) FX FY FZ Gauges deviation FX FY FZ Gauges 17 2 45° 120 91% 89% 96% 96% 92% 84% 87%  89% 96% 17 bis 2 bis 45° 166 91% 94% 99% 95% 98% 63% 84% 100% 98%

[0062] The values of 95% for the averages of the correlations are very high, thereby indicating that the time profile of the signals related to the chicken and those related to the impactor are close while the amplitude ratio is of the same order as the ratio of the incident energies, which means that, with identical energy, the impactor applies deformations equivalent to those of a chicken.

[0063] FIG. 3 shows an example of view, under a microscope, of the microbeads within a projectile according to the invention. In this example of embodiment, the microbeads are made of phenolic resin and have a diameter lower than 200 μm. On this picture, the size of the present microbeads is between 10 μm and 130 μm.