Method of producing a filament wound curved product and product obtained thereby

Abstract

The invention relates to a curved product, and in particular an armor product. The armor product is produced by a filament winding process in which a plurality of reinforcing elements in the form of fibers and/or tapes are impregnated with a polymer matrix and wound onto a mandrel. The polymer matrix comprises a solution and/or dispersion of a polymer in a carrier fluid, which carrier fluid is at least partly evaporated during and/or after winding. The armor product comprises a high amount of reinforcing elements with respect to the total mass of the product.

Claims

1. A filament winding process for producing a 3D curved product comprising: (a) winding a plurality of reinforcing elements having a tensile strength of at least 1.6 GPa onto a mandrel which substantially approximates an inner shape of the 3D curved product to form a 3D curved fiber structure preform having a shape which substantially approximates the 3D curved product, (b) impregnating the plurality of reinforcing elements or the 3D curved fiber structure preform with a polymer matrix comprised of a solution and/or a dispersion of a polymer in a carrier fluid, (c) at least partly evaporating the carrier fluid from the solution and/or dispersion during and/or after winding the reinforcing elements onto the mandrel according to step (a), (d) consolidating the 3D curved fiber structure preform under elevated pressure onto the mandrel to thereby form the 3D curved fiber structure preform having a shape which substantially approximates the 3D curved product, (e) cutting the 3D curved fiber structure preform thereby also removing the mandrel, and (f) subjecting the fiber structure to a subsequent pressing process at elevated temperature and pressure to form the 3D curved product, wherein the reinforcing elements are present in an amount of at least 85% of the total mass of the 3D curved product.

2. The filament winding process according to claim 1, wherein the reinforcing element is a fiber.

3. The filament winding process according to claim 1, wherein the reinforcing element is a tape.

4. The filament winding process according to claim 1, wherein the reinforcing element is aramid.

5. The filament winding process according to claim 1, wherein the reinforcing element is ultrahigh molecular weight polyethylene.

6. The filament winding process according to claim 1, wherein the reinforcing element is glass fiber, carbon fiber, poly(p-phenylene-2, 6-benzobisoxazole) fiber, poly(2,6-diimidazo-(4,5b-4,5e)pyridinylene-1,4(2,5-dihydroxy)phenylene) fiber, and polyethylene or polypropylene fibers, and/or combinations of the above fibers.

7. The filament winding process according to claim 1, wherein the polymer matrix comprises a thermoplastic polymer.

8. The filament winding process according to claim 1, wherein the polymer matrix comprises polyvinyls, polyacrylics, polyolefins, thermoplastic elastomeric block copolymers, polyisopropene-polyethylene-butylene-polystyrene, or polystyrene-polyisoprene-polystyrene block copolymers.

9. The filament winding process according to claim 1, wherein the filaments are positioned according to a pattern that is geodetic.

10. The filament winding process according to claim 1, wherein the fiber structure has a wall thickness of at least 3 mm.

11. The filament winding process according to claim 1, further comprising pressing the fiber structure to obtain a pressed product.

12. The filament winding process according to claim 11, wherein the pressed product is an armor product.

13. The filament winding process according to claim 11, wherein the pressed product is a helmet.

14. The filament winding process according to claim 11, wherein the pressed product is a radome.

15. A filament winding process for producing a 3D curved product comprising: (a) winding a plurality of reinforcing elements having a tensile strength of at least 1.6 GPa onto a mandrel which substantially approximates an inner shape of the 3D curved product to form a 3D curved fiber structure having a shape which substantially approximates the 3D curved product such that when positioned on a flat surface the 3D curved fiber structure has a ratio of maximum elevation with respect to the flat surface relative to a largest linear dimension within a projected surface of the 3D curved fiber structure onto the flat surface of at least 0.20, (b) impregnating the plurality of reinforcing elements or the 3D curved fiber structure with a polymer matrix comprised of a solution and/or a dispersion of a polymer in a carrier fluid, (c) at least partly evaporating the carrier fluid from the solution and/or dispersion during and/or after winding the reinforcing elements onto the mandrel according to step (a), (d) consolidating the 3D curved fiber structure under elevated pressure onto the mandrel to thereby form a 3D curved fiber structure preform having a shape which substantially approximates the 3D curved product, (e) cutting the 3D curved fiber structure preform thereby also removing the mandrel, and (f) subjecting the 3D curved fiber structure preform to a subsequent pressing process at elevated temperature and pressure to thereby form the 3D curved product, wherein the reinforcing elements are present in an amount of at least 85% the total mass of the 3D curved product.

16. The filament winding process according to claim 15, wherein the ratio of maximum elevation to the largest linear dimension within a projected surface of the 3D curved product onto the flat surface is at least 1.00.

Description

EXAMPLES I AND COMPARATIVE EXPERIMENT A

(1) Antiballistic Dyneema UHMWPE fibers of type SK76 1760 dTex were wound onto a mandrel in the shape of a combat helmet. The mean tension of the fibers was about 14 N during winding. The fibers were impregnated with an aqueous dispersion (mixing ratio 1:1 on a weight basis) of a Kraton thermoplastic polymer. After winding the produced helmets were dried in an oven at about 80 C. during 24 hours to evaporate the water from the polymer matrix. The density of the matrix material after drying is 1040 kg/m.sup.3. The dried helmet preforms were then further consolidated under vacuum in an autoclave at a temperature of about 100 C. during 2.5 hours. Compression pressure was about 20 bar. After autoclave moulding the cylindrical product thus produced was cut into two halves, thereby also removing the mandrel. The two product halves were then post-processed by pressing them in a press between two metal moulds at a temperature of 125 C. and at a maximum pressure of about 165 bar during 45 minutes.

(2) The characteristics of the helmets produced according to the invention are summarized in Table 1.

(3) TABLE-US-00001 TABLE 1 characteristics of produced helmets. Example I Thickness [mm] 5.5 Surface area [cm2] 1295 Weight [kg] 0.98 Pressure moulded Yes

(4) Testing was performed according to the STANAG 2920 standard. Typical V50 values for conventionally produced helmets made from 38 ply Dyneema HB25 at a temperature of 125 C. and at a maximum pressure of about 165 bar during 45 minutes are 622 m/sec for a helmet with a thickness of 7.8 mm, and 730 m/sec for a helmet with a thickness of 9.2 mm (46 ply Dyneema HB25).

(5) Results obtained are summarized in Table 2.

(6) TABLE-US-00002 TABLE 2 anti-ballistic results Areal Density [kg/m.sup.2] V.sub.50 [m/s] E.sub.abs [J/kg/m.sup.2] Example I 5.5 564 31.8 Comparative 8.7 622 24.4 Experiment A

(7) When assuming that the V.sub.50 is linearly dependent on the thickness, a conventionally produced helmet of 5.5 mm thickness would accomplish a V.sub.50 of 438 m/s, whereas the filament wound helmet according to the invention (Example I) obtained a V50 of 564 m/s which is 126 m/s higher.

(8) The known helmet (Comparative Experiment A) made out of 38 plies HB25 has a V.sub.50 of 622 m/s and an areal density of 7.8 kg/m2. The absorbed energy E.sub.abs for this helmet is therefore (0.5*m.sub.FSP*V.sup.2.sub.50)/AD=24.4 J/kg/m.sup.2. The absorbed energy of the filament wound helmet is higher, so the filament wound helmet performed better.

(9) Based on the amount of energy a helmet can absorb, a filament wound helmet according to the invention performs better than a conventionally pressed helmet. The typical value for the absorbed energy of a conventional helmet is 24.4 J/kg/m.sup.2. The absorbed energy of a helmet according to the invention lies above 32.4 J/kg/m.sup.2, a performance increase of at least 30%. Adding to the performance increase the filament winding process offers other advantages such as the absence of wrinkles in the final product, the cheaper starting materials (yarns+resin vs. cross-ply prepreg), the freedom of combining different materials, the low amount of waste and the opportunity for far-reaching automation.