HIGH PERFORMANCE FIBERS COMPOSITE SHEET
Composite sheets include at least two adjacent fibrous monolayers of unidirectionally aligned high tenacity polyethylene fibers, whereby the direction of orientation between the polyethylene fibers of said two fibrous layers differs by at least 80° and up to 90°, the fibers having a tenacity of at least 1.5 N/tex, the fibers being in a matrix comprising a homopolymer or copolymer of ethylene and wherein the homopolymer or copolymer of ethylene has a density as measured according to ISO1183 of between 870 to 980 kg/m 3 . The composite sheets have an areal density of between 50 and 500 g/m 2 , wherein the composite sheets have an areal density normalized in-plane shear force measured at 25° C. evaluated according to a bias extension test method variant of ASTM D3518 of at least 0.40 N·m 2 ·g −1 and lower than 5.0 N·m 2 ·g −1 at 10 mm clamp displacement and an areal density normalized in-plane shear force measured at 110° C. and clamp displacement of 10 mm of at least 0.01 N·m 2 ·g −1 and lower than 0.20 N·m 2 ·g −1 .
1 . A composite sheet comprising:
a matrix comprising a homopolymer or copolymer of ethylene having a density as measured according to ISO1183 of between 870 to 980 kg/m 3 , and
at least two adjacent fibrous monolayers of unidirectionally aligned high tenacity polyethylene fibers impregnated with the matrix, wherein a direction of orientation between the polyethylene fibers of the at least two fibrous layers differs by at least 80° and up to 90°, wherein the fibers have a tenacity of at least 1.5 N/tex, and wherein
the composite sheet has an areal density of between 50 and 500 g/m 2 wherein the composite sheet has an areal density normalized in-plane shear force measured at 25° C. evaluated according to a bias extension test method variant of ASTM D3518 of at least 0.40 N·m 2 ·g −1 and lower than 5.0 N·m 2 ·g −1 at 10 mm clamp displacement and an areal density normalized in-plane shear force measured at 110° C. and clamp displacement of 10 mm of at least 0.01 N·m 2 ·g −1 and lower than 0.20 N·m 2 ·g −1 .
2 . The composite sheet according to claim 1 , wherein the areal density normalized in-plane shear force measured at 25° C. of the composite sheet is at least 0.50 N·m 2 ·g −1 and lower than 3.0 N·m 2 ·g −1 .
3 . The composite sheet according to claim 1 , wherein the areal density normalized in-plane shear force measured at 25° C. of the composite sheet is at least 0.60 N·m 2 ·g −1 and lower than 2.0 N·m 2 ·g −1 .
4 . The composite sheet according to claim 1 , wherein the areal density normalized in-plane shear force measured at 25° C. of the composite sheet is at least 0.70 N·m 2 ·g −1 and lower than 1.5 N·m 2 ·g −1 .
5 . The composite sheet according to claim 1 , wherein the areal density normalized in-plane shear force measured at 25° C. of the composite sheet is at least 0.90 N·m 2 ·g −1 and lower than 1.5 N·m 2 ·g −1 .
6 . The composite sheet according to claim 1 , wherein the areal density normalized in-plane shear force measured at 25° C. of the composite sheet is at least 1.0 N·m 2 ·g −1 and lower than 1.5 N·m 2 ·g −1 .
7 . The composite sheet according to claim 1 , wherein the areal density normalized in-plane shear force measured at 110° C. of the composite sheet is at least 0.03 N·m 2 ·g −1 and lower than 0.10 N·m 2 ·g −1 .
8 . The composite sheet according to claim 1 , wherein the areal density normalized in-plane shear force measured at 110° C. of the composite sheet is at least 0.04 N·m 2 ·g −1 and lower than 0.08 N·m 2 ·g −1 .
9 . The composite sheet according to claim 1 , wherein the areal density normalized in-plane shear force measured at 110° C. of the composite sheet is at least 0.05 N·m 2 ·g −1 and lower than 0.06 N·m 2 ·g −1 .
10 . The composite sheet according to claim 1 , wherein the composite sheet has an areal density normalized in-plane shear secant stiffness at 1% longitudinal deformation of at least 30 N·m 2 ·g −1 and less than 200 N·m 2 ·g −1 , the in-plane shear secant stiffness being measured at 25° C. according to the bias extension test.
11 . The composite sheet according to claim 1 , wherein the composite sheet has an areal density normalized in-plane shear secant stiffness at 1% longitudinal deformation of at least 40 N·m 2 ·g −1 and less than 150 N·m 2 ·g −1 , the in-plane shear secant stiffness being measured at 25° C. according to the bias extension test.
12 . The composite sheet according to claim 1 , wherein the composite sheet has an areal density normalized in-plane shear secant stiffness at 1% longitudinal deformation of at least 50 N·m 2 ·g −1 and less than 100 N·m 2 ·g −1 , the in-plane shear secant stiffness being measured at 25° C. according to the bias extension test.
13 . The composite sheet according to claim 1 , wherein the composite sheet has an areal density normalized in-plane shear secant stiffness at 1% longitudinal deformation of at least 60 N·m 2 ·g −1 and less than 100 N·m 2 ·g −1 , the in-plane shear secant stiffness being measured at 25° C. according to the bias extension test.
14 . The composite sheet according to claim 1 , wherein the composite sheet has an areal density normalized in-plane shear secant stiffness at 1% longitudinal deformation of at least 0.5 N·m 2 ·g −1 and less than 7.0 N·m 2 ·g −1 , the in-plane shear secant stiffness being measured at 110° C. according to the bias extension test.
15 . The composite sheet according to claim 1 , wherein the composite sheet has an areal density normalized in-plane shear secant stiffness at 1% longitudinal deformation of at least 1.0 N·m 2 ·g −1 and less than 5.0 N·m 2 ·g −1 , the in-plane shear secant stiffness being measured at 110° C. according to the bias extension test.
16 . The composite sheet according to claim 1 , wherein the composite sheet has an areal density normalized in-plane shear secant stiffness at 1% longitudinal deformation of at least 1.5 N·m 2 ·g −1 and less than 3.0 N·m 2 ·g −1 , the in-plane shear secant stiffness being measured at 110° C. according to the bias extension test.
17 . The composite sheet of claim 1 , comprising from 2 to 25 wt % of the homopolymer or copolymer of ethylene, based on the total weight of the composite sheet.
18 . The composite sheet of claim 17 , wherein the matrix comprises an ethylene acrylic acid (EAA) copolymer, an ethylene methacrylic acid (EMA) copolymer or mixtures thereof.
19 . A ballistic resistant article comprising at least one composite sheet as defined in claim 1 .
20 . The ballistic resistant article of claim 19 , wherein the article is a compression molded panel which comprises at least 10 of the composite sheets.