(19)
(11) EP 0 310 203 A1

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication:
05.04.1989 Bulletin 1989/14

(21) Application number: 88202164.5

(22) Date of filing: 30.09.1988
(51) International Patent Classification (IPC)4D02G 3/40, D02G 3/48, D03D 15/00, D04H 1/42
(84) Designated Contracting States:
AT BE CH DE ES FR GB GR IT LI NL SE

(30) Priority: 02.10.1987 DE 3733444

(71) Applicant: STAMICARBON B.V.
NL-6167 AC Geleen (NL)

(72) Inventor:
  • Timmermans, Hubertus Theodorus Marie
    NL-6003 PB Weert (NL)


(56) References cited: : 
   
       


    (54) Combination of filaments having substantially different damping responses to mechanical vibrations in a matrix, and use thereof


    (57) The invention relates to combinations of fila­ments having substantially different damping responses to mechanical vibrations in a matrix, the filaments hav­ing good damping properties being present in an amount of about 30 to 50% by volume of the total quantity of filaments. The filaments having high damping properties are in particular filaments made of polyethylene of ultra­high molecular weight and the filaments having low damp­ing properties are glass fibers or carbon fibers. The composite articles produced from the filaments, which are embedded in a matrix, in particular a matrix made of epoxy resin, are preferably suitable for producing skis, hockey sticks, tennis rackets, robot arms, machine hou­sings, angling rods, competition bows or the like.


    Description


    [0001] The present invention relates to a combination of filaments having substantially different damping re­sponses to mechanical vibrations in a matrix.

    [0002] With many structural parts incorporating compo­site materials which are reinforced with fibers or fila­ments, the situations under load incured cause incidental vi bra­tions or oscillations of high frequency. These vibra­tions or oscillations are generally undesirable, since they lead to premature fatiguing of the material or have an adverse effect on the performance characteristics of the structure. There are existing composite materials composed of graphite, glass and Kevlar fibers and fila­ments embedded in a matrix in order to have a positive effect on the damping properties of structural parts. Nonetheless, structural parts which are produced in this known manner are subject to undesirable vibrations or oscillations. In addition, composite materials based on graphite, glass and Kevlar fibers or filaments are expensive.

    [0003] It is an object of the present invention to pro­vide a composite material of high strength combined, at the same time, with good internal damping.

    [0004] This object is achieved according to the inven­tion by combinations of filaments having substantially different damping responses to mechanical vibrations, preferably filaments having high internal damping and consisting of highly drawn filaments of polymers having ultrahigh molecular weight and high tensile strengths and also moduli and filaments of low internal damping, for example glass fibers or carbon fibers, being embed­ded in a matrix made preferably of epoxy resin. Other suitable materials for the matrix are unsaturated poly­ester, polyethylene, vinyl or thermoplastics.

    [0005] The filaments of high internal damping have pre­ferably been produced by the gel process with subsequent drawing to high draw ratios. In a preferred embodiment, the filaments of high internal damping consist of poly­mers having an ultrahigh molecular weight of more than 600,000 g/mol (weight average of molecular weight), in particular polyolefins.

    [0006] Replacing a portion of the filaments of low in­ternal damping with filaments of high internal damping and made in particular of a polyethylene of ultrahigh molecular weight gives a hybrid structure which, depend­ing on the proportion of filaments of high internal damp­ing, is adaptable to the purposes required. Preferably, the filaments of high internal damping are present in a proportion from 30 to 50% by volume of the total quantity of filaments in the composite material or combination.

    [0007] A gel process whereby the filaments of high in­ternal damping are preferably produced is described for example in GB-A-2,042,414 and -2,051,667 and also in DE Offenlegungsschrift 3,724,434 and comprises essentially dissolving the particular polymer used for filament produc­tion in a solvent, molding the solution at a temperature above the dissolving temperature of the polymer into a filament, cooling the filament, for gelling, down to a temperature below the dissolving temperature and drawing the filament with solvent removal. The polymer used for producing the filaments of high internal damping can be of any desired type, for example polyolefins, polyesters, polyamides, as also polyacrylonitrile, polyvinyl alcohol, polyvinyl chloride etc.

    [0008] Preferably, the filaments of high internal damp­ing consist of polymers of ultrahigh molecular weight, in particular polyolefins, particular preference being given to polyethylenes, in particular linear polyethy­lenes. These polyethylenes may contain minor amounts, preferably not more than 5 mol-%, of one or more other alkenes copolymerizable therewith, such as propylene, butylene, pentene, hexene, 4-methylpentene, octene etc. and have 1 to 10, in particular 2 to 6, methyl or ethyl groups per 1,000 carbon atoms. It is also possible to use other polyolefins, for example polypropylene homo­polymers and copolymers. Furthermore, the polyolefins used may also contain minor amounts of one or more other polymers, in particular alkene-1 polymers.

    [0009] Preferably, the filaments of high internal damp­ing have an oscillation damping factor of more than 20 . 10⁻³. Filaments made of polyethylene of ultrahigh molecular weight have an internal damping factor of more than 100 . 10⁻³.

    [0010] The filaments of high internal damping and of low internal damping are preferably embedded in a plastic matrix, made in particular of epoxy resin, polyester, polyethylene or the like. In a preferred embodiment, the filaments of low internal damping are arranged around the filaments of high internal damping.

    [0011] The combination of fibers of high internal damp­ing and fibers of low internal damping in a matrix improves the dynamic behavior of the composition as a consequence of the high damping capacity of the filaments, made for example of polyethylene of ultrahigh molecular weight, and as a consequence of the high energy absorption by the filament/­matrix interface, in particular if the filaments consist of a polyethylene of ultrahigh molecular weight and matrix of epoxy resin. The composite materials made of filaments of high internal damping, filaments of low internal damping and a matrix in which the filaments are embedded are prefer­ably suitable for producing skis, hockey sticks, tennis rac­kets, arms for industrial robots, machine housings, angling rods, competition bows or the like. In the composite mater­ial the polyethylene filaments of ultrahigh molecular weight are preferably covered with glass fibers. In the event of oscillations this prevents the polyethylene fibers from emerging and projecting out of the matrix. Moreover, the composite article can be covered with a nonwoven to produce a smooth surface.

    Examples:



    [0012] 

    1. A vibration test (RES ME 87 0037 MT-AC) at fre­quencies from 100 to 310 Hz revealed the follow­ing damping factors for fibers embedded in an epoxy matrix:
    Carbon fibers in epoxy matrix: damping factor
    3 . 10⁻³
    Glass fibers in epoxy matrix: damping factor
    6 . 10⁻³
    Kevlar fibers in epoxy matrix: damping factor
    10 . 10⁻³
    Fibers made of PE of ultrahigh molecular weight in epoxy matrix: damping factor
    20 . 10⁻³

    2. Torsion damping test (RVD no. 00 00 33).
    The test specimens were hybrid structures compo­sed of glass fibers and fibers made of PE of ultrahigh molecular weight in an epoxy matrix and composed of glass fibers in a epoxy matrix.



    [0013] 
    Temperature T (°C) Proportion of glass fibers Proportion of PE fibers tan
    76% 0% 0.9 x 10⁻²
    35% 41% 2.8 x 10⁻²
    20° 76% 0% 1.2 x 10⁻²
    35% 41% 4.0 x 10⁻²
    40° 76% 0% 2.4 x 10⁻²
    35% 41% 5.8 x 10⁻²


    [0014] It has been found that the damping of the hybrid structure is 2.5 to 3 times better than the internal damp­ing of glass fibers in an epoxy matrix.


    Claims

    1. A combination of filaments having substantially different damping responses to mechanical vibrations in a matrix.
     
    2. A combination as claimed in claim 1, wherein the filaments are present in the form of yarns, fabrics, blends and/or nonwovens.
     
    3. A combination as claimed in claim 1 or 2, wherein the bulk of the filaments consists of filaments of low internal damping.
     
    4. A combination as claimed in any one of claims 1 to 3, wherein the filaments of high internal damping account for 30 to 50% by volume of the total quantity of filaments.
     
    5. A combination as claimed in any one of claims 1 to 4, wherein the filaments of high internal damping consist of highly drawn filaments of polymers having a high molecular weight and high tensile strengths and also moduli.
     
    6. A combination as claimed in claim 5, wherein the filaments have been produced by the gel process and sub­sequent drawing to high draw ratios.
     
    7. A combination as claimed in any one of claims 1 to 6, wherein the filaments of high internal damping con­sist of polymers having an ultrahigh molecular weight of more than 600,000 g/mol (weight average of molecular weight), in particular polyolefins.
     
    8. A combination as claimed in any one of claims 1 to 7, wherein the filaments of low internal damping are glass fibers or carbon fibers and have an internal damp­ing factor of less than 10 . 10⁻³.
     
    9. A combination as claimed in any one of claims 1 to 8, wherein the matrix in which the filaments are embed­ded comprises a plastics material.
     
    10. A combination as claimed in claim 9, wherein the plastics material is polyester, epoxy, polyethylene or the like.
     
    11. A combination as claimed in any one of claims 1 to 10, wherein the filaments of low internal damping are arranged around the filaments of high internal damping.
     
    12. Use of a combination as claimed in any one of claims 1 to 11 for producing composite materials for skis, hockey sticks, tennis rackets, robot arms, machine hou­sings, angling rods, competition bows or the like.
     





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