JP2008068437A - Honeycomb sandwich panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a honeycomb sandwich panel which can minimize deformation by moisture absorption even when the humidity of an external environment is changed. <P>SOLUTION: In the sandwich panel, both surfaces of a honeycomb core composed of a carbon fiber-reinforced carbon composite material woven from carbon fibers are held between skins composed of the same kind of material. One orientation direction of the carbon fibers is made an approximately vertical direction to the surfaces of the skins. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a honeycomb sandwich panel having high dimensional stability, which is applied to a reflector rear structure and an optical support structure of a telescope used in outer space or on the ground.

  With the advancement of science and technology in recent years, there has been a demand for higher performance of telescopes used in outer space and on the ground. Future telescopes, including next-generation telescopes, will have a reflector rear structure and support structure for telescopes. In honeycomb sandwich panels used for optical structures such as these, there are increasing demands for light weight, high rigidity, low thermal expansion, low thermal strain, and the like. A honeycomb sandwich panel is obtained by sandwiching both surfaces of a honeycomb core of a carbon fiber reinforced carbon composite material composed of reinforcing fibers such as carbon fibers with plate-like members called skins. Usually, the skin is also composed of a carbon fiber reinforced carbon composite material.

  A honeycomb core composed of a carbon fiber reinforced carbon composite material woven with conventional carbon fibers is required to be lightweight and highly rigid. Therefore, the orientation direction of the carbon fibers in the honeycomb core is hexagonal. The direction was ± 45 ° with respect to the rotational symmetry axis direction of the honeycomb (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 5-124874 (2 pages, FIG. 1)

  A prototype of a reflector with a honeycomb sandwich panel using a honeycomb core in which the orientation direction of the conventional carbon fiber is ± 45 ° with respect to the rotational symmetry axis direction of a hexagonal honeycomb was evaluated. It was found that the reflection characteristics (focal length, etc.) of the reflecting mirror changed. It was also found that the honeycomb sandwich panel was deformed due to changes in humidity.

  An object of the present invention is to provide a honeycomb sandwich panel that can suppress deformation to a minimum even when the humidity of the external environment changes, since it has been made to solve the above-described problems.

  As a result of detailed investigation and analysis of the deformation of the honeycomb sandwich panel due to humidity changes in the external environment, the honeycomb sandwich panel composed of carbon fiber, which is an inorganic material system, has not been affected by humidity. Although it was considered, it was found that the honeycomb core, which is a constituent member of the honeycomb sandwich panel, was deformed by moisture absorption. Further, since the fiber orientation of the reinforcing fibers of the honeycomb core is in the direction of ± 45 ° with respect to the surface of the skin, the binding force of the honeycomb core is weak in the thickness direction and the in-plane direction of the honeycomb sandwich panel. It has been found that the core cannot be fully restrained from deformation when it absorbs moisture.

  A honeycomb sandwich panel according to the present invention is a honeycomb sandwich panel in which both sides of a honeycomb core composed of a carbon fiber reinforced carbon composite material woven with carbon fibers are sandwiched between skins, in one direction of fiber orientation of carbon fibers, The direction is substantially perpendicular to the surface of the epidermis.

  In the honeycomb sandwich panel according to the present invention, one direction of fiber orientation of the carbon fibers of the honeycomb core composed of the carbon fiber reinforced carbon composite material woven with carbon fibers is substantially perpendicular to the surface of the skin. Therefore, the amount of deformation of the honeycomb sandwich panel due to moisture absorption can be made almost zero.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram showing the structure of a honeycomb sandwich panel in the first embodiment for carrying out the present invention. FIG. 2 is a schematic diagram of the honeycomb core 3 in the present embodiment. In FIG. 1, a honeycomb sandwich panel 1 is configured by sandwiching a honeycomb core 3 from both sides with two skins 2. In FIG. 2, the honeycomb core 3 is composed of a carbon fiber reinforced carbon composite material woven with carbon fibers, and the cell size is about 1/4 inch (the cell size is the size of the hexagonal diagonal of the honeycomb). ), The thickness is about 25 mm. The carbon fiber reinforced carbon composite material is obtained by impregnating Toray's Torayca T300 (registered trademark) carbon fiber with an epoxy resin, followed by carbonization heat treatment to carbonize the epoxy resin. The fiber orientation directions of the carbon fibers constituting the honeycomb core 3 are 0 ° and 90 ° with respect to the rotational symmetry axis direction 4 of the hexagonal honeycomb as shown in FIG. A direction perpendicular to the surface of the skin 2 is 0 ° with respect to the rotational symmetry axis direction 4 of the honeycomb, that is, a direction parallel to the rotational symmetry axis direction 4.

  The skin 2 is also composed of a carbon fiber reinforced carbon composite material woven with carbon fibers. A Torayca T300 (registered trademark) cloth C06343 (trade name) of Toray is impregnated with a phenol resin to produce a prepreg sheet, After cutting it into an appropriate size, a plurality of sheets are laminated and heat-cured and molded, and then subjected to carbonization heat treatment.

  Using honeycomb core 3 and skin 2 obtained by carbonization heat treatment, both sides of honeycomb core 3 are sandwiched between two skins 2 as shown in FIG. Heat treatment was performed to carbonize the binder component of the carbon-based adhesive to obtain a honeycomb sandwich panel 1 composed entirely of carbon fiber reinforced carbon composite material.

  The amount of deformation due to moisture absorption of the honeycomb sandwich panel configured as described above was evaluated. FIG. 3 is a schematic diagram of a method for measuring the deformation amount of the honeycomb sandwich panel used in the present embodiment.

  First, the measurement method will be described. In FIG. 3, the honeycomb sandwich panel 6 that is symmetrical to the measurement and the reference 7 made of quartz are arranged side by side on the support fixing portion 5, and the end portion of the honeycomb sandwich panel 6 opposite to the support fixing portion 5 and the reference The total reflection mirror 8 is installed so as to be in contact with the end portion of 7 at the same time. The honeycomb sandwich panel 6 is arranged in a direction in which the direction parallel to the surface of the skin is perpendicular to the support fixing portion 5. The half mirror 9 is arranged in parallel with the total reflection mirror 8 in the vicinity of the total reflection mirror 8, and the laser light 11 is irradiated from the laser interferometer 10 to the half mirror 9. If the parallel interval between the total reflection mirror 8 and the half mirror 9 is slightly shifted, interference occurs between the laser light reflected by the half mirror 9 and the laser light transmitted through the half mirror 9 and reflected by the total reflection mirror 8. In the laser interferometer 10, interference fringes 12 are observed. Since the reference 7 is made of quartz, it hardly deforms due to changes in temperature or humidity. However, when the honeycomb sandwich panel 6 is deformed (expanded or contracted) due to temperature or humidity, the total reflection mirror 8 is inclined as shown in FIG. Since the tilt is not parallel to the half mirror 9, the interference fringes 12 observed by the laser interferometer 10 change. Actually, although the interval of the interference fringes 12 changes, in order to confirm more intuitively, the number of interference fringes 12 observed in a certain visual field was evaluated. In addition, the space | interval of the interference fringe 12 becomes narrow, that is, the number of the interference fringes 12 increases means that the honeycomb sandwich panel 6 as the measurement object has expanded. It can be seen that the honeycomb sandwich panel 6 is deformed by the change in the number of the interference fringes 12.

  Next, a method for measuring deformation with respect to humidity in the present embodiment will be described. The honeycomb sandwich panel obtained in the present embodiment is sufficiently dried by holding it at about 120 ° C. for 50 hours in a vacuum using a vacuum oven. The sufficiently dried honeycomb sandwich panel is set in an apparatus shown in FIG. 3 installed in a constant temperature and humidity chamber in which the atmosphere is kept constant at a temperature of 25 ° C. and a humidity of 55%. When exposed to an atmosphere of constant humidity for a long time, the honeycomb sandwich panel 6 gradually absorbs moisture and deforms, and the number of interference fringes 12 observed by the laser interferometer 10 changes.

  In the present embodiment, for comparison, a honeycomb sandwich panel composed of a honeycomb core having the same fiber orientation direction as that of the conventional carbon fiber was also produced, and the deformation amount was measured by the same method. As a comparative example, the carbon fiber constituting the honeycomb core has a fiber orientation direction of ± 45 ° with respect to the rotational symmetry axis direction 4 of the honeycomb. In addition, the same honeycomb sandwich panel whose deformation was measured was left in a constant temperature and humidity chamber at the same time, and when the interference fringes were observed, the weight was measured, and the amount of change (the change in weight since fully dried) Rate) was calculated.

  FIG. 5 is a characteristic table showing the relationship between the time left in a constant temperature and humidity chamber, the number of interference fringes, and the weight change rate. As can be seen from this table, in the comparative example, there was an increase in weight of about 0.8% due to moisture absorption after standing for 100 hours, and the number of interference fringes also increased from 4 to 26. It can be seen that the honeycomb sandwich panel has expanded. On the other hand, the honeycomb sandwich core of the present embodiment has a weight increase due to moisture absorption of about 0.2% even after being left for 100 hours, but the number of interference fringes is not changed and is hardly deformed. Recognize. From the above results, the direction of the fiber orientation of the carbon fibers constituting the honeycomb core is made substantially perpendicular to the surface of the skin, so that the amount of deformation of the honeycomb sandwich panel due to moisture absorption can be made almost zero. .

Embodiment 2. FIG.
FIG. 6 is a schematic diagram of the honeycomb core 3 used in the honeycomb sandwich panel in the second embodiment. In the present embodiment, the material of the carbon fiber constituting the honeycomb core 3 is the same as in the first embodiment, but there are three fiber orientation directions, one direction being the rotationally symmetric axial direction 4 of the hexagonal honeycomb. However, the remaining two directions are ± 60 ° with respect to the rotationally symmetric axis direction 4. A direction perpendicular to the surface of the skin 2 is 0 ° with respect to the rotational symmetry axis direction 4 of the honeycomb, that is, a direction parallel to the rotational symmetry axis direction 4. Using this honeycomb core 3, a honeycomb sandwich panel was produced in the same manner as in the first embodiment.

  The deformation due to moisture absorption of the honeycomb sandwich panel in the present embodiment was measured by the same method as in the first embodiment. Also in the present embodiment, as in Embodiment 1, a comparative example in which the direction of fiber orientation of the carbon fibers constituting the honeycomb core was ± 45 ° with respect to the rotationally symmetric axis direction of the honeycomb was simultaneously measured. . FIG. 7 is a characteristic table showing the relationship between the standing time, the number of interference fringes, and the weight change rate when the honeycomb sandwich panel of the present embodiment is left in a temperature and humidity chamber. As can be seen from this table, compared to the comparative example, the honeycomb sandwich core of this embodiment has a weight increase of about 0.2% even after being left for 100 hours, but the number of interference fringes is not changed. It can be seen that there is almost no deformation. From the above results, the direction of the fiber orientation of the carbon fibers constituting the honeycomb core is made substantially perpendicular to the surface of the skin, so that the amount of deformation of the honeycomb sandwich panel due to moisture absorption can be made almost zero. .

  In Embodiments 1 and 2 described above, TORAYCA T300 (registered trademark) of PAN (polyacrylonitrile) -based carbon fiber is used as the carbon fiber of the honeycomb core, but other highly elastic PAN-based carbon fiber is used. Alternatively, high-strength PAN-based carbon fibers or pitch-based carbon fibers may be used. Moreover, although the epoxy resin is used for the resin of the honeycomb core, a resin that can be carbonized by a heat treatment such as a phenol resin or an aramid resin may be used. Similarly, various PAN-based or pitch-based carbon fibers may be used as the material for the skin. Although a carbon-based adhesive is used as the adhesive, it may be bonded using a ceramic-based adhesive or the like. For example, Aron ceramics may be used and the organic binder may be volatilized by heating after bonding.

  Furthermore, in the above-described embodiment, the cross-sectional shape of the honeycomb core has been described as a hexagonal shape (honeycomb) shape. However, the honeycomb core shape may be a semicircular shape, a circular shape, or a combination of polygonal shapes of triangles or more May be.

It is a schematic diagram which shows the structure of the honeycomb sandwich panel in Embodiment 1 of this invention. It is a schematic diagram which shows the structure of the honeycomb core in Embodiment 1 of this invention. FIG. 3 is a schematic diagram of a method for measuring a deformation amount of a honeycomb sandwich panel according to Embodiment 1 of the present invention. FIG. 3 is a schematic diagram of a method for measuring a deformation amount of a honeycomb sandwich panel according to Embodiment 1 of the present invention. It is a characteristic table | surface of the honeycomb sandwich panel in Embodiment 1 of this invention. It is a schematic diagram which shows the structure of the honeycomb core in Embodiment 2 of this invention. It is a characteristic table of the honeycomb sandwich panel in Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Honeycomb sandwich panel 2 Skin 3 Honeycomb core 4 Rotation symmetry axis 5 Support fixing part 6 Honeycomb sandwich panel 7 Reference 8 Total reflection mirror 9 Half mirror 10 Laser interferometer 11 Laser beam 12 Interference fringe

Claims (3)

In a honeycomb sandwich panel in which both sides of a honeycomb core composed of a carbon fiber reinforced carbon composite material woven with carbon fibers are sandwiched by a skin composed of the same material as the honeycomb core,
A honeycomb sandwich panel, wherein one direction of fiber orientation of the carbon fibers of the honeycomb core is a direction substantially perpendicular to the surface of the skin. The honeycomb sandwich panel according to claim 1, wherein the other direction of fiber orientation of the carbon fibers of the honeycomb core is a direction substantially perpendicular to one direction of fiber orientation of the carbon fibers. The honeycomb sandwich panel according to claim 1, wherein the other direction of the fiber orientation of the carbon fibers of the honeycomb core is approximately 60 ° and -60 ° with respect to the one direction of the fiber orientation of the carbon fibers.

Images