Multilayered material sheet and process for its preparation
The invention relates to a multilayered material sheet comprising a consolidated stack of unidirectional monolayers of drawn polymer. The draw direction of two subsequent monolayers in the stack differs. Moreover the strength to thickness ratio of at least one monolayer is larger than 4.5.10 13 N/m 3 . The invention also relates to a ballistic resistant article comprising the multilayered material sheet and to a process for the preparation of the ballistic resistant article.
1. A ballistic resistant article comprising a multilayered material sheet comprising:
a consolidated stack of multiple unidirectional film monolayers comprised of a plurality of drawn anti-ballistic polymer film tapes having a stretch factor of at least 9 and a tensile strength of at least about 1.2 GPa, wherein
adjacent monolayers in the stack have respective draw directions which differ from one another, and wherein
the film tapes in the stack have an areal density of from 5 g/m 2 to less than 50 g/m 2 and a strength to thickness ratio which is larger than 4.5×10 13 N/m 3 .
2. The ballistic resistant article according to claim 1 , wherein the film tapes or monolayers have a strength to thickness ratio which is larger than 7×10 13 N/m 3 .
3. The ballistic resistant article according to claim 1 , which comprises a binder.
4. The ballistic resistant article according to claim 1 , wherein the thickness of the film monolayers is between 3 and 25 μm.
5. The ballistic resistant article according to claim 4 , wherein the tensile strength of the drawn film tapes in the film monolayers is at least about 4 GPa.
6. The ballistic resistant article according to claim 1 , wherein the polymer comprises ultra high molecular weight polyethylene.
7. The ballistic resistant article according to claim 1 , wherein the draw directions of the adjacent monolayers in the stack differ by an angle α of between 45 and 135°.
8. The ballistic resistant article according to claim 1 , wherein adjacent drawn film tapes in the film monolayers do not overlap.
9. The ballistic resistant article according to claim 1 , wherein at least one of the film monolayers comprises a plurality of woven unidirectional film tapes of the drawn polymer.
10. The ballistic resistant article according to claim 1 , comprising at least 4 unidirectional monolayers.
11. The ballistic resistant article according to claim 1 , comprising a further sheet of material selected from the group consisting of ceramic, steel, aluminum, magnesium titanium, nickel, chromium and iron or their alloys, glass and graphite, or combinations thereof.
12. The ballistic resistant article according to claim 11 , wherein the further sheet of material is positioned at an outside of the stack of monolayers at least at a strike face thereof.
13. The ballistic resistant article according to claim 11 , wherein the further sheet of inorganic material has a thickness which is at most 50 mm.
14. The ballistic resistant article according to claim 11 , further comprising a bonding layer between the material sheet and the further sheet of material, wherein the bonding layer comprises a woven or non-woven layer of inorganic fibers.
15. The ballistic resistant article according to claim 1 , wherein the drawn anti-ballistic polymer film tapes have a stretch factor of at least 25.
16. The ballistic resistant article according to claim 7 , wherein the angle α is between 80 and 100°.
17. The ballistic resistant article according to claim 1 , wherein the ballistic resistant article has an E-abs ballistic performance value which is at least twice the E-abs ballistic performance value of an identical comparative ballistic resistant article of the same areal density but having monolayers in the stack with a strength to thickness ratio lower than 4.5×10 13 N/m 3 determined after two stops and two penetrations of the articles with 9 mm parabellum projectiles and 17 grain fragment simulating projectiles (FSP).
18. The ballistic resistant article according to claim 1 , wherein the ballistic resistant article has an E-abs ballistic performance value which is at least twice the E-abs ballistic performance value of an identical comparative ballistic resistant article of the same areal density but having film tapes in the stack which have an areal density of greater than 50 g/m 2 determined after two stops and two penetrations of the articles with 9 mm parabellum projectiles and 17 grain fragment simulating projectiles (FSP).
19. The ballistic resistant article according to claim 1 , wherein the film tapes in the stack have an areal density of less than 29 g/m 2 .
20. The ballistic resistant article according to claim 1 , wherein the film tapes in the stack have an areal density of less than 25 g/m 2 .
21. A process for the manufacture of a ballistic resistant article according to claim 1 comprising:
(a) stacking the multilayered material sheet and a sheet of material selected from the group consisting of ceramic, steel, aluminum, titanium, glass and graphite, or combinations thereof; and
(b) consolidating the stacked sheets under temperature and pressure.