Unidirectional long fiber three dimensional fiber structure produced by short fiber intertwining and production method thereof

#1. Field of the Invention

#The present invention relates to a unidirectional long fiber three dimensional fiber structure suitable for use as a fiber reinforced material formed complicated shape preform for a composite material used in aircraft and spacecraft structures, ships, and vehicles and the like, as well as a method of producing such a structure.

#2. Description of the Related Art

#FIG. 1(A) to FIG. 1(C) are cross-sectional views of three dimensional fiber structures.

#FIG. 1(D) is a perspective view showing needlepunch of the three dimensional fiber structure of FIG. 1(A).

#FIG. 2(A) is a perspective view of a die for producing a three dimensional fiber structure.

#As follows is a description of preferred embodiments of the present invention, based on the drawings. FIG. 1(A) through FIG. 1 (C) are sample cross-sections of unidirectional three dimensional fiber structures 41, 42, and 43 of the present invention, showing circular, square, and triangular cross-sections, respectively. In addition to these shapes, the present invention can also be applied to any other arbitrary cross-sectional shape, including polygons of 5 or more sides, ellipses, star shapes, H shapes, I shapes, Y shapes and other irregular shapes. The unidirectional three dimensional fiber structure is produced by performing needlepunch from a plurality of directions, as shown in the unidirectional three dimensional fiber structure 41 of circular cross-section shown in FIG. 1(D). By conducting needlepunch in this manner, the individual long fibers 44 are intertwined and integrated by nap-like fibers 45 which extend in a plurality of directions, as shown in the enlarged view of FIG. 1(A).

#The unidirectional three dimensional fiber structure 41 can be produced, for example, using a cylindrical die 47 in which a straight aperture 46 has been opened, as shown in FIG. 2. This aperture 46 within the die 47 is preferably a tapered aperture in which the internal diameter narrows gradually from an inlet 46a at one end of the aperture through to an outlet 46b at the other end, as shown in FIG. 2(B). By employing such a construction, the insertion of the long fibers 44 can be achieved smoothly, while the density of the long fibers 44 at the outlet can be increased.

#A plurality of needle holes 48 are formed which extend through the side wall of the die 47 and into the aperture 46, and three dimensional multiaxial needlepunch of the long fibers 44 inside the die 47 is conducted through these needle holes 48. As shown in FIG. 2(C), a 90° zone, a +45° zone and a −45° zone can be arranged sequentially along the length of the aperture 46, starting at the inlet side 46a, and needlepunch is then performed at an angle of 90° , +45° and −45° respectively within each of these zones. In addition, as shown in FIG. 2(D), needlepunch is also performed from, for example, three different angles around the periphery of the aperture 46. According to this type of construction, nap-like fibers 45 are forced out in a plurality of directions from each long fiber 44, and these nap-like fibers 45 become intertwined with the nap-like fibers 45 from other long fibers 44, thereby binding the plurality of long fibers 44 into a single integrated unit, as shown in FIG. 1(A).