JPH07112721B2 - Method for manufacturing honeycomb sandwich panel - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon fiber reinforced plastic (CFR) suitable as a structural material or interior material for an aircraft.
P) as a skin and a method for producing a sandwich panel having a honeycomb body as a core.

[0002]

2. Description of the Related Art A honeycomb sandwich panel having CFRP as a skin and a honeycomb body as a core is conventionally manufactured by adhering a skin CFRP plate to the honeycomb body. First of all, this adhesion is the CFR that becomes the skin.
After sanding the part of the P plate that becomes the adhesion surface with the honeycomb body and cleaning it by washing with acetone or the like, apply an adhesive or attach an adhesive film, and then attach the CFRP plate to the honeycomb body. , So that the adhesive-coated surface or the adhesive film-bonded surface is on the honeycomb body side,
It is carried out by placing it in an autoclave and heating and pressurizing it to bond the CFRP plate and the honeycomb body. However, in this method, since it is necessary to separately form a CFRP plate that serves as a skin, the number of steps is large and the manufacturing cost is high.

On the other hand, a method generally called a co-cure molding method has been proposed in which the molding of the skin and the adhesion to the honeycomb body are simultaneously performed. In this method, a prepreg of a carbon fiber woven fabric and a honeycomb body are overlapped with each other, and the prepreg and the honeycomb body are pressed under heating to cure the resin of the prepreg to form a skin and to bond the skin and the honeycomb body. However, the number of steps is smaller than that of the method described above, and the manufacturing cost can be reduced. However, on the other hand, there are problems as described below, which are caused by the fabric constituting the prepreg.

That is, as is well known, a carbon fiber yarn is produced by firing precursor fiber yarn (multifilament yarn) such as polyacrylonitrile fiber in an inert atmosphere to carbonize it. Most of the manufacturing cost of the carbon fiber yarn is occupied by this firing step, and the quality of the productivity in the firing step has a great influence on the cost of the carbon fiber thread and eventually the woven fabric.

The productivity in the firing process is improved as the thicker precursor fiber yarn is used. Since it can be fired at a stretch, the thinner the product, the worse the productivity and the higher the cost of the fabric. However, if the cost of textiles rises, CF
Since the ratio of material cost to RP increases, cost performance decreases, and the limitation of applications increases, the precursor fiber yarn usually has several thousand single yarns,
Sometimes I use thick ones that exceed 10,000. Therefore, the carbon fiber yarn obtained from such a thick precursor fiber yarn is naturally also thick and brings various disadvantages to the woven fabric.

That is, in a woven fabric, the thicker the weaving yarn, the greater the bending of the weaving yarn due to the interlacing. However, as is clear from the mechanics, when there is a bend, stress concentrates on that portion, so that the characteristics originally possessed by the carbon fiber cannot be fully utilized. This is because the breakage of the woven fabric begins to occur from the bent portion before the characteristics of the carbon fiber are exhibited.

Further, when the bending of the weaving yarn becomes large, the texture becomes large and the surface irregularities also become large. The texture and unevenness are increased by the fact that the carbon fiber has high rigidity and the converging force due to the interlacing acts on the yarn. However, if the texture becomes large or the irregularities become large, the CFR
When it is set to P, a part where carbon fiber does not exist at all is formed due to uneven distribution of carbon fiber, or a part where resin is excessive is formed, so that it is difficult to obtain CFRP excellent in not only physical properties but also reliability.

When a prepreg is formed by impregnating the woven fabric as described above with a thermosetting resin of B stage under heating, the prepreg is heated and the viscosity of the thermosetting resin is lowered. Due to the pressing, the weaving yarn is widened, the weave is almost closed, and the surface irregularities are almost eliminated.
This seems to be preferable at first glance, but this is a result of the fact that the highly rigid single fiber of carbon fiber was forcibly moved by the pressurization, and when the pressurization was released, it was completely in the original state. If not, it will recover to a state close to it.

When such a woven prepreg and a honeycomb body are superposed and heated and pressed to cure a thermosetting resin to form a skin, the skin and the honeycomb body are adhered to each other to produce a honeycomb sandwich panel. ,
The woven fabric is pressed in the cell wall part to move the single yarn, but the above-mentioned recovery state is almost maintained as it is not pressed in the cell hole part. Fibers may be completely absent, resin may be excessive, or voids may be formed between the prepreg layers. However, if such a honeycomb sandwich panel is used to construct an aircraft spoiler, for example, moisture will collect in the voids, which will freeze during flight at high altitude, causing cracks in the skin, and so on. Moisture will infiltrate into the honeycomb body, and the physical properties of the panel will be deteriorated, which will hinder the safe operation of the aircraft.

In the first place, CFRP is not an isotropic material like a metal material, but an anisotropic material, so that the design itself is difficult, and there are also various subtle problems in the reinforcing material, which makes it difficult to design. Is made even more difficult, which makes reliability one step less reliable.
Although CFRP is used in aircraft as an advanced material with excellent properties such as specific strength and specific elastic modulus, its use is limited to secondary structural materials, and its use as a primary structural material whose destruction affects flight safety. This is also the reason why hesitates.

[0011]

An object of the present invention is to solve the above-mentioned problems in the conventional method for manufacturing a honeycomb sandwich panel, and to provide a carbon fiber woven fabric constituting a prepreg in which the bending of the weaving yarn in the intersecting portion is small. It is not only necessary to worry about the problem of fracture due to stress concentration, but also using a woven fabric that has excellent surface smoothness and can avoid most of the inconveniences due to uneven distribution of carbon fibers. It is an object of the present invention to provide a method for manufacturing a sandwich panel which is expensive and highly reliable at low cost.

[0012]

In order to achieve the above-mentioned object, the present invention is designed by designing a multifilament yarn of carbon fiber as a warp yarn and a weft yarn.
The relationship between the width and the fineness is, respectively, an expression, W = k · (D / ρ) ^5/9 , where W: the width of the warp or weft (mm) k: a coefficient of 3.5 × 10 ⁻² to 10 ^0.0 × 10 ^-2 (mm · d ^-5/9 ) D: ^{Fineness of} warp or weft ( d: Denier) ρ: Satisfies the specific gravity of carbon fiber and has a cover factor of 90 to 9
A prepreg of a carbon fiber woven fabric in the range of 9.8% and a honeycomb body are superposed on each other, and the prepreg and the honeycomb body are pressed under heating to cure the resin of the prepreg to form a skin and the skin and the honeycomb. Provided is a method for manufacturing a honeycomb sandwich panel, which is characterized by adhering to a body.

The carbon fiber woven fabric used in the present invention is composed of multifilament yarns of carbon fiber as woven yarns, that is, warp yarns and weft yarns. The warp yarns and the weft yarns each have a relationship between the width and the fineness expressed by the formula: W = K · (D / ρ) ^5/9 However, W: width of warp or weft (mm) k: coefficient, 3.5 × 10 ^{−2 to} 10.0 × 10 ⁻² (mm · d ^{−5 / 9} ) D: Fineness of warp or weft ( d: Denier) ρ: Satisfies the specific gravity of carbon fiber, and has a cover factor of 90 to 9
It is in the range of 9.8%. Such fabrics are
For example, it can be manufactured as follows.

That is, first, by a normal weaving operation,
A woven fabric having carbon fiber multi-filament yarns as woven yarns, that is, warp yarns and weft yarns is obtained.

The number of single filaments of the multifilament yarn is taken into consideration in view of easiness of weaving operation and improvement of uniformity of dispersion of single filaments in the woven yarn in the opening, widening and flattening treatments described later.
3,000 to 30,000, denier 1,
It is preferably about 200 to 40,000 denier. The single yarn diameter is about 5 to 10 μm. The multifilament yarn preferably has a twist number of 5 times / m or less in order to facilitate the opening, widening and flattening treatment and to have excellent uniformity. From the viewpoints of opening, widening and flattening, it is most preferable that no twist is formed, but if there is no twist, weaving operation is difficult.

When weaving a woven fabric using the above-mentioned carbon fiber multifilament yarn as a woven yarn, the subsequent opening, widening and flattening treatment can be performed easily and uniformly, and the cover factor is within a specific range. Therefore, the gaps formed between the warp yarns and the weft yarns, that is, the weaves, are set to be slightly wider than those of ordinary woven fabrics. The extent to which the warp is widened depends on the thickness of the weaving yarn, but is at least ⅕ of the width of the warp. For example, if the width of the warp is 1.5 mm, 0.5 mm
Before and after.

Most preferably, the weave of the fabric is a flat weave. Usually, as warp and weft, yarns having the same number of single yarns and the same fineness are used, and the weaving density is made equal in the warp direction and the weft direction.

On the other hand, although the basis weight can be arbitrarily selected, when the number of single yarns of the weaving yarn is small, the spreadability, the widening / flattening treatment is easy, the uniformity, the shape retention of the obtained woven fabric, and the cover factor are obtained. Considering the above, preferably 120 to 250 g /
m ² , more preferably in the range of 140 to 195 g / m ² . This weight range is particularly preferable when the number of single yarns is 3,000. In addition, the basis weight is opened, widened,
It does not change even after the flattening process.

Next, while the above-mentioned woven fabric is continuously run in the warp direction, the warp yarn and the warp yarn are directed to the woven fabric from a plurality of nozzles arranged in a row in the weft direction of the woven fabric. Open the weft and widen and flatten it.

The nozzle diameter is preferably in the range of 0.05 to 0.5 mm. If it is less than 0.05, the amount of water is small, and even if the beating force on the surface of the woven fabric is increased, sufficient energy may not be obtained to open the woven yarn and widen / flatten it. Also, it becomes easy to become clogged. On the other hand, 0.5
On the other hand, if it exceeds mm, the amount of water will be too large, and depending on the hitting force, adjacent water jets will interfere with each other on the surface of the fabric, and the single yarns that make up the weaving yarn will become irregular. Bending may occur, and the uniformity of spreading, widening and flattening of the weaving yarn may decrease.

The nozzle pitch is preferably 1/3 or less of the warp pitch of the woven fabric. When the nozzle pitch exceeds 1/3, the unevenness of the energy distribution of the water jet on the surface of the woven fabric becomes large, and in extreme cases, a weaving yarn in which the water jet is not directed appears,
The uniformity of opening, widening, and flattening of the weaving yarn may decrease.

Further, it is preferable that the water jet has a striking force on the surface of the fabric within the range of 0.1 to 3 gf. If it is less than 0.1 gf, the striking force may be too small to obtain the energy required for opening, widening and flattening the woven yarn. On the other hand, if it exceeds 3 gf, the striking force is too large, the single yarn breaks frequently, the broken single yarns are fluffed, and the uniformity of the opening, widening and flattening of the woven yarn is easily deteriorated.

The warp and weft of the woven fabric thus obtained have a relationship between the width and the fineness as expressed by the formula: W = k · (D / ρ) ^5/9 , where W: width of the warp or weft (mm) k : Coefficient: 3.5 × 10 ^{-2 to} 10.0 × 10 ^-2 (mm · d ^-5/9 ) D: ^{Fineness of} warp or weft ( d: Denier) ρ: Satisfies the specific gravity of carbon fiber There is. A woven fabric satisfying this condition has a very uniform opening, widening and flattening of the weaving yarn, very little bending due to crossing, and excellent surface smoothness. It should be noted that k in the above formula is related to the degree and uniformity of opening, widening and flattening of the woven yarn, and when k is below the lower limit value, widening and flattening is not sufficiently advanced. Therefore, the bending due to the interlacing of the weaving yarns is large, and the unevenness of the surface is also large. Also,
If the upper limit is exceeded, the spread of the fibers is uneven.

The resulting woven fabric has a cover factor in the range of 90 to 99.8%. Here, the cover factor (C _f ) relates to the size of the weave, and when a region having an area S ₁ is set on the woven fabric, the area S ₁
And the total sum S ₂ of the areas of the textures existing in the region,
It is obtained by the equation, C _f = [(S ₁ −S ₂ ) / S ₁ ] × 100. The larger the cover factor, the more the weaving yarn is opened, the wider and flattened, and the smaller the weave. The cover factor is 100%, that is, the weave is completely closed, in the sense that it avoids the formation of carbon fiber-free areas, resin-rich areas, and voids. It seems to be preferable. However, such a woven fabric is too poor in drape property because the binding force between the woven yarns is too strong and the freedom of movement of the woven yarns is too small.
Wrinkles are likely to occur. Although very small, it is extremely important to make a gap between the weaving yarns so as to have a degree of freedom of deformation. And in this invention,
The upper limit of the cover factor is set to 9 in consideration of the balance between the above-mentioned degree of opening and widening / flattening of the woven yarn and the drapeability.
It is 9.8%. On the other hand, if it is less than 90%, the drape property is excellent but the texture is too large. The cover factor is preferably measured as follows.

That is, first, using a stereomicroscope, for example, a stereomicroscope SMZ-10-1 manufactured by Nikon Corporation, the front surface of the fabric is photographed while shining light from the back side of the fabric. As a result, the transmitted light pattern of the fabric in which the weaving yarn portion is black and the weave portion is white is photographed. The amount of light is set in the range that does not cause halation. In the present invention, the light of the double arm fiber manufactured by Nikon Corporation is reflected by an acrylic plate and used. The photographing magnification is set within 10 times so that 2 to 20 warps and 2 wefts are included in the analysis range in the subsequent image analysis. next,
The obtained photograph is photographed by a CCD (charge coupled device) camera, the photographed image is converted into digital data representing black and white lightness and stored in a memory, which is analyzed by an image processing device, and the total area S ₁ is obtained. , The total area S ₂ of the white portions and the cover factor are calculated based on the above-mentioned formula. The same thing is done 10 times for the same woven fabric, and the simple average value is taken as the cover factor in the present invention. In this invention, a personal image analysis system LA-525 manufactured by Pierce Co. was used as the CCD camera and the image processing device. In the horizontal direction, the analysis range of the image is from the left end of the leftmost warp thread to the leftmost end of the warp thread, and the vertical direction is the lowest end of the top weft thread. Up to the upper end of the weft, and the warp and the weft are each 2
I tried to enter ~ 20. In addition, in digital data,
An intermediate portion between black and white is included in the boundary between the weaving yarn portion (black portion) and the texture portion (white portion). In order to distinguish this intermediate portion into the weaving yarn portion and the weave portion, as a model, a black tape with a width of 6 mm is attached in a grid pattern vertically and horizontally at intervals of 6 mm so that the cover factor becomes 75%. Standardized to. That is, the aperture of the CCD camera is set to 2.8, and the memory value of the image analysis system LA-525 is 128.
The following portions were standardized as the woven yarn portion (in this system, black and white light and dark are stored as memory values of 0 to 255 levels).

Among the above-mentioned woven fabrics, multifilament yarns of carbon fibers having the same number of single yarns and the same fineness are flat-structured as warp and weft. The warp and weft have a relation of width and fineness as expressed by the formula: W = k ・ (D / ρ) ^5/9 However, W: width of warp or weft (mm) k: coefficient, 3.5 × 10 ^{-2 to} 10.0 × 10 ^-2 (mm ・d ^-5/9 ) D: Fineness of warp or weft ( d: Denier) ρ: Satisfies the specific gravity of carbon fiber, the weaving density is equal in the warp and weft directions,
Those having a basis weight of 120 to 250 g / m ² and a cover factor of 90 to 99.8% can be particularly preferably used in the present invention. It is more preferable to use a multifilament yarn having a single yarn number of 3,000.

That is, except for a special woven fabric, the woven fabric has large anisotropy because the woven yarns extend in two directions orthogonal to each other, but the warp and weft have the same number of single yarns and fineness, and Woven fabrics having the same weaving density in the warp direction and the weft direction have the same characteristics in the directions orthogonal to each other. Therefore, when the warp yarns or the weft yarns are laminated and used so as to be offset by a specific angle, for example, 45 °, Pseudo-isotropy can be easily obtained. Also, in terms of manufacturing method, the number of single yarns of warp and weft,
When the fineness is the same and the weaving density is the same in the warp direction and the weft direction, the size of the weave is the same in the warp direction and the weft direction,
Widening and flattening can be easily done by spreading the weaving thread equally in both directions.

Further, with the flat design, it is possible to obtain a thin woven fabric having a stable design with less deviation of the weave.

Further, in the case of a woven fabric in which the number of single yarns of warp and weft is the same, the fineness is the same, and the basis weight is in the range of 120 to 250 g / m ² , the bending of the woven yarn in the intersecting part is smaller and the stress concentration The destruction problem can be avoided more reliably. In addition, surface irregularities are also reduced. Weight is 120g
If it is less than / m ² , the cover factor becomes too small,
If it exceeds 250 g / m ² , the bending of the woven yarn becomes too large. Even in terms of manufacturing method, a fabric having a fabric weight in such a range has a small binding force between the weaving yarns due to the interlacing even though it has a flat design, and the size of the fabric is also small. Can easily open, widen and flatten. The more preferable weight range is 140 to 195 g /
m ² .

In the present invention, the above-mentioned woven fabric is heated with a thermosetting resin such as an epoxy resin, an unsaturated polyester resin, a phenol resin, a polyimide resin or a bismaleimide resin in the B stage by a conventional method. Is pressure-impregnated into a prepreg. Since the woven yarn is sufficiently opened, widened and flattened, even during impregnation,
When the pressure is released after impregnation, the single yarn hardly moves. The proportion of thermosetting resin in the prepreg is
Since this thermosetting resin is also used as an adhesive for bonding the skin and the honeycomb body, it is preferable to set it in a range of 36 to 44% by weight, which is slightly higher than that of a normal prepreg. In addition, various fillers and rubbers may be added to the thermosetting resin for the purpose of adjusting the viscosity thereof.

In the present invention, next, the desired number of prepregs are laminated on each side of a honeycomb body such as an aluminum honeycomb body or a paper honeycomb body, and the prepreg and the honeycomb body are pressed under heating. The resin of the prepreg is cured to form a skin, and the skin and the honeycomb body are bonded together. At this time, the prepreg fabric is pressed in the cell wall portion of the honeycomb body and is not pressed in the cell hole portion, but since the woven yarn is sufficiently opened, widened and flattened, Almost no movement occurs.

The molding can be carried out by a compression molding method, but it is preferable to use a known autoclave molding method.
Molding temperature is 120-180 ℃, molding pressure is 2-8kg / cm
^{2 is} enough.

Each skin is usually of the same construction, but one of the skins, for example, the skin on the inner surface side when in use,
It is also possible to use a normal woven prepreg made of glass fiber or polyaramid fiber, or a unidirectional prepreg. Further, these prepregs can be used together by being sandwiched between the layers of the woven prepreg described above.

[0034]

[Example] Carbon fiber "Torayca" T300 yarn manufactured by Toray Industries, Inc. with a twist number of 0.8 times / m (average single yarn diameter: 7 μm, single yarn number: 3,000, fineness: 1,800 denier, specific gravity 1.76) as the woven yarn, that is, the warp and the weft, and the widths of the warp and the weft are 1.47 mm and 1.4, respectively.
9 mm, the warp and weft direction weave sizes are 0.57 mm and 0.59 mm, and the warp and weft direction weave densities are both 4.85 yarns / cm (warp pitch: about 2.06 m
m), a plain-woven fabric having a basis weight of 194 g / m ² and a thickness of 0.31 mm was obtained.

Next, the above woven fabric was subjected to fiber-spreading, widening and flattening treatment using a water jet while running in the warp direction at a speed of 1.5 m / min. At this time, the nozzle hole diameter was 0.13 mm, the nozzle pitch was 0.6 mm, and the striking force per water jet was 0.6 gf.

The woven fabric thus obtained is well opened,
The widths of the warp and weft are 1.71 mm and 1.91 mm, respectively
Was widened and flattened. Also, the thickness is 0.28 mm,
The cover factor was about 99%, which was thin, and the surface irregularities were extremely small. Furthermore, single yarn breakage and fluff generation were not observed.

Next, the woven fabric prepreg was obtained by impregnating the above-mentioned woven fabric under pressure with heating at 120 ° C. so that the B-stage epoxy resin was 38% by weight. Even with this heating and pressure impregnation, the movement of the single yarn hardly occurred.

Next, one piece of the woven prepreg is placed on an aluminum plate coated with a silicone release agent, and the weaving direction of the prepreg is ± 45 with respect to the weaving thread of the prepreg woven fabric having the direction of the weaving yarn first. The cell hole size is 1/8 inch (about 3.2 mm) and the thickness is 1 /
A 2-inch (about 12.7 mm) aramid honeycomb body (honeycomb body made of aramid paper impregnated with heat-resistant phenolic resin) is placed, and two prepregs are further placed on the aramid honeycomb body. Was placed so as to be mirror-symmetric with the first two prepreg fabrics placed with respect to the thickness center of the aramid honeycomb body, and the whole was packed with a fluororesin film.

Next, the above-mentioned pack body is put into an autoclave, and while the pressure inside the pack body is reduced, the pack body is heated to 180 ° C. at a rate of 1.5 ° C./minute under a pressure of 3 kg / cm ² , and the temperature is raised to 2 ° C.
After holding for a time, the epoxy resin of the woven fabric prepreg was cured to form a skin, and the skin and the honeycomb body were bonded together.

The cross section of the honeycomb sandwich panel thus obtained was observed, and it was found that carbon fibers were extremely uniformly dispersed in the skin. Moreover, no void was observed.

[0041]

INDUSTRIAL APPLICABILITY The present invention, as a prepreg fabric,
A multifilament yarn of carbon fiber is organized as warp and weft, and the relationship between width and fineness of each warp and weft is expressed by the formula: W = k · (D / ρ) ^5/9 where W: warp or weft Width (mm) k: coefficient, 3.5 × 10 ^{-2 to} 10.0 × 10 ^-2 (mm · d ^-5/9 ) D: fineness of warp or weft ( d: denier) ρ: carbon fiber And the cover factor is 90 to 9
In the range of 9.8%, the woven yarn is very uniformly opened, widened and flattened, and the bending due to the crossing is very small,
Since a woven fabric having excellent surface smoothness is used, the conventional problem was the so-called co-cure molding method.In the cell wall portion of the honeycomb body, the woven fabric was pressed and movement of the single yarn occurred.
The carbon fibers are unevenly distributed due to not being pressed in the cell hole parts, and thus, there may be a part where the carbon fibers do not exist at all in the skin, a resin excessive part may be formed, or a void may be formed between the prepregs laminated. Inconvenience can be solved, and a honeycomb sandwich panel having high physical properties and excellent reliability can be obtained. So also with this, for example, when configuring an aircraft spoiler, moisture collects in the voids, freezing during flight at high altitudes and causing cracks in the skin,
In addition, it is possible to prevent the inconvenience that the moisture penetrates into the honeycomb body after repeating this process, and the physical properties of the panel are deteriorated, which hinders safe operation of the aircraft. In addition, when used as an interior material for aircraft, carbon fibers that never burn in the skin are evenly dispersed, and since the cover factor is large, it is expected to have the effect of preventing the penetration of flame in the event of a fire. it can. Further, according to the present invention, the so-called co-cure molding method is adopted, and the molding of the skin and the bonding with the honeycomb body are performed at the same time, so that the number of steps is small and the honeycomb sandwich panel can be manufactured at low cost.

Claims (2)

[Claims] 1. A carbon fiber multifilament yarn is designed as a warp yarn and a weft yarn, and the warp yarn and the weft yarn each have a relationship between the width and the fineness expressed by the formula: W = k · (D / ρ) ^5/9 , W: width of warp or weft (mm) k: coefficient, 3.5 × 10 ^{-2 to} 10.0 × 10 ^-2 (mm ・d ^-5/9 ) D: fineness of warp or weft ( d: denier ) Ρ: The specific gravity of the carbon fiber is satisfied, and the cover factor is 90 to 9
The prepreg of the woven fabric and the honeycomb body in the range of 9.8% are superposed, and the prepreg and the honeycomb body are pressed under heating to cure the resin of the prepreg to form a skin and the skin and the honeycomb body. A method for manufacturing a honeycomb sandwich panel, which comprises bonding 2. A woven fabric is flat-structured with multifilament yarns of carbon fibers having the same number of single yarns and fineness as warps and wefts, and each of the warps and wefts has a formula, W = k.multidot. (D / ρ) ^5/9 However, W: width of warp or weft (mm) k: coefficient, 3.5 × 10 ^{-2 to} 10.0 × 10 ^-2 (mm ・d ^-5/9 ) D : Fineness of warp or weft ( d: denier) ρ: Satisfies the specific gravity of carbon fiber, the weaving density is the same in the warp direction and the weft direction,
The method for producing a honeycomb sandwich panel according to claim 1, which is a woven fabric having a basis weight of 120 to 250 g / m ² and a cover factor of 90 to 99.8%.