Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Staple length fiber
Reexamination Certificate
2002-06-14
2004-08-17
Dixon, Merrick (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Staple length fiber
C428S357000, C428S383000, C428S364000, C428S371000, C428S375000, C428S376000, C428S379000, C428S397000, C428S401000, C428S407000, C264S439000, C264S443000, C264S450000, C264S459000
Reexamination Certificate
active
06777081
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a reinforcing structure, comprising metallic elements, and the use of such reinforcing structure to reinforce stiff composite articles. The invention further relates to stiff composite articles and a method to provide stiff composite articles.
BACKGROUND OF THE INVENTION
Reinforcing structure are known to reinforce polymer articles. Often, glass fibers or C-fibers are used to reinforce polymer matrices, providing together a reinforced, eventually shaped article. During forming processes, the bending properties of the polymer matrix are influenced negatively, since the reinforcing structures are difficult to elongate.
Often, metallic filaments or fibers are integrated into composite materials in order to obtain a material that is EMI shielded. As a result of electromagnetic requirements, metallic filaments or fibers with fine diameters of 100 &mgr;m or less are used. An example of this can be found in U.S. Pat. No. 5,089,326. It is known in the art that the addition of fine metallic fibers or filaments, usually less than 100 &mgr;m, does not increase the strength of the composite material.
Metal wires or metal wire textile fabrics are also known as reinforcing structures, e.g. from FR1290278, EP234463A1, EP546962A1 or EP392904A1. To improve the deformability of the composite material, metal wires are preferably provided as knitted fabrics.
SUMMARY OF THE INVENTION
The present invention relates to a reinforcing structure comprising metallic elements. The reinforcing structure can be used to manufacture stiff composite articles, which further comprises a polymer matrix.
It is an object of the present invention to provide a reinforcing structure which comprises metallic elements, all metallic elements laying essentially parallel to each other, which has improved bending properties compared to the known wires or wire meshes, and which provide an alternative to the knitted wire structures.
A reinforcing structure as subject of the invention comprises metallic elements, which are all essentially parallel to each other in the reinforcing structure, wherein each of the metallic elements are structurally deformed. By “essentially parallel, ” it is meant that due to the nature of the metallic elements, the distance between adjacent metallic elements may vary only slightly.
In the scope of the present invention, metallic elements are to be understood as metallic wires, e.g. drawn metallic wires, a bundle of metallic wires, metallic strands or cords.
As subject of the invention, the bending properties of reinforcing structure are improved by integrating metallic elements in the reinforcing structure, which have an elongation at rupture of more than 3% compared to initial length. This elongation can even be more than 5% or more than 7%, e.g. more than 10% and most preferentially more than 15% at rupture.
According to the invention, this elongation is obtained by the use of a metallic element having structural deformations. Such structural deformation may have an irregular shape, e.g. undulated with a wavelength and/or amplitude, which varies over the length to the metallic element. Preferably however, the metallic element are undulated or spirally shaped in a regular way, with constant parameters over the whole length of the metallic element.
A structural deformation can be e.g. an undulation. The metallic element, being a wire, strand or cord, is given a form, characterized by a wavelength and an amplitude. This undulated metallic element is essentially comprehended in one plane, parallel to the axis of the metallic element. Another structural deformation can be that e.g. a metallic element has obtained a spiral shape, characterized by a diameter of the spiral and the length of the metallic element, necessary to make a 360° revolution in the spiral shape.
In case the metallic element is undulated, this undulation being the structural deformation, the removal of the structural deformation of the metallic element will lead to an elastic elongation, a plastic elongation, or a combination of both of the metallic element during the forming process, mainly depending on the wavelength of the undulation.
In case a small wavelength is used, e.g. less than 3 mm, a higher force will be necessary to elongate the metallic element, so removing the structural deformation, next to the elastic and plastic elongation of the metallic element under load as if there was no structural deformation. The removing of this structural deformation leads to a mainly plastic elongation of the metallic element. When the metallic element is released, the metallic element will not come back to its original undulated form, but will stay elongated to certain extend.
In case a longer wavelength is applied, e.g. more than 3 mm or even more than 4.5 mm, a lower force is sufficient to stretch the metallic element, so removing to some extend the structural deformation. This leads to a mainly elastic elongation of the metallic element, which is additional to the elastic elongation of the metallic element under low force as if there was no structural deformation. When the metallic element is released, the metallic element will come back to approximately its original undulated form. When higher forces are applied, a plastic elongation of the metallic element itself is found, next to the removal of the remaining structural deformation.
The elongation of the metallic elements being undulated with a large wavelength, can be more than 0.3%, e.g. more than 0.4%, or even more than 0.5%, preferably more than 1% or more, applying a force of 10% of the force at rupture of the metallic element.
In case the metallic element has a spiral shape structural deformation, an identical behavior is obtainable. Depending on the length to make a 360° rotation and the diameter of the spiral, the removal of the structural deformation of the metallic element will lead to an elastic elongation, a plastic elongation or a combination of both of the metallic element during the forming process.
One understands that the elongation due to a removing of the structural deformation, can be either elastic, or plastic or a combination of a plastic and an elastic elongation, depending on the wavelength or the length to make a 360° revolution applied.
Metallic elements, being part of a reinforcing structure as subject of the invention, may have more than one structural deformation, being e.g. undulations or spiral shape structural deformations, superposed one to another.
When a metallic element having two structural deformations, being two undulations of which one has a large wavelength and the second having a short wavelength, is subjected to an elongation force F, a stress-strain curve comprising different successive zones, limited by forces F
1
, F
2
, F
3
and F
4
(F
1
<F
2
<F
3
<F
4
), is obtained.
For a force F applied less than F
1
, an elastic elongation is obtained. When a force F larger than F
1
, but less than F
2
is applied, an additional, essentially plastic elongation is added. These elongations can be explained by the mainly removing of the structural deformation with large wavelength.
When the force F is increased to a level between F
2
and F
3
, the additional elongation again is mainly elastic. When F is increased to a level between F
3
and F
4
, the elongation in this zone becomes mainly plastic, until rupture occurs at F
4
. These two later elongations are mainly explained by the removal of the structural deformation with short wavelength, and the plastic deformation of the metallic element without structural deformation until rupture.
The forces F
1
, F
2
and F
3
, where the elongation change from elastic to plastic or vice versa, can be adjusted by the wavelength and amplitude of the undulations together with other parameters of the metallic element, such as diameter of wires, alloy and drawing history and eventually strand and cord construction.
In case more than 2 structural deformations are superposed to each other, a similar behavior of the metallic element under load can be obtaine
Boesman Peter
De Clercq Elsie
Van Giel Frans
Dixon Merrick
Foley & Lardner
N.V. Bekaert S.A.
LandOfFree
Reinforcing structure for stiff composite articles does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reinforcing structure for stiff composite articles, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reinforcing structure for stiff composite articles will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3287415