JP4103768B2 - FRP hollow structure molding method and core used in this molding method - Google Patents

Description

  The present invention relates to a method for forming an FRP hollow structure and a core used in the method, and more particularly to a method for forming an FRP hollow structure having a beam structure therein and a core used in the method. Is.

  Conventionally, as a suitable manufacturing method for manufacturing an FRP structure having a complicated shape, a plurality of structural members constituting the FRP structure are each molded by a prepreg, and each structural member is temporarily molded in a semi-cured state. Subsequently, a method has been proposed in which structural members are combined to form a preform, and the preform is cured to manufacture a FRP structure (see, for example, Patent Document 1).

Here, according to Patent Document 1, each structural member formed by the prepreg is subjected to a semi-curing treatment in which the reaction rate of the matrix resin is 0.2 to 0.8, that is, the curing depth (Cure Index) is 20. A semi-curing treatment of ˜80% is performed, and in this state, each structural member is combined as a preform.
JP 2000-15710 A

  By the way, as described in Patent Document 1, each structural member subjected to the semi-curing treatment with a curing depth of 20 to 80% hardly flows even when reheated, and has a soft gel surface. There is a great risk that the adhesiveness (tackiness) will not develop. For this reason, even if each structural member is combined as a preform and cured, each structural member may not be firmly bonded, and there is a concern that a strong FRP structure cannot be produced unless an adhesive is used in combination. is there.

  In general, a core is used to manufacture a hollow FRP structure, but the core needs to be removed after the FRP structure is formed. That is, there is a problem in that the process of removing the core becomes indispensable for the production of the hollow FRP structure, and the number of steps increases.

  Therefore, the present invention has an object to provide a method for forming an FRP hollow structure capable of reliably forming a strong FRP hollow structure having a beam structure therein while eliminating a core removal step. In addition, an object of the present invention is to provide a core suitable for use in this FRP hollow structure molding method.

  A method for forming an FRP hollow structure according to the present invention is a method for forming an FRP hollow structure having a beam structure therein, and an inner shell preform having a beam structure by laminating a prepreg on a tool having a predetermined shape. A part preform molding process for molding a part preform for each part of the above, an inner shell preform assembling process for assembling each molded part preform as an inner shell preform, and preheating the assembled inner shell preform A preheating and curing step for curing to a predetermined curing depth (Cure Index), and an outer preform forming step for forming an outer preform by laminating a prepreg on the outer periphery of the preheated inner shell preform as a core. And a main heating and curing step in which the outer preform and the outer shell preform are heated and cured in the mold. In the preheating curing step, the inner shell preform is cured to a curing depth of 5 to 15%.

  In the method for forming an FRP hollow structure according to the present invention, the inner shell preform cured to a curing depth of 5 to 15% by the preheating and curing step has a high dimensional accuracy due to an increase in surface hardness. It functions reliably as a core when molding the outer preform by the molding process. In addition, the inner shell preform cured to a curing depth of 5 to 15% is softened and fluidized by reheating by the main heating and curing process, so that adhesiveness is developed. Adhering well to each other is surely integrated.

  Accordingly, in the FRP hollow structure molding method according to the present invention, the beam structure is obtained through the parts preform molding process, the inner shell preform assembling process, the preheating curing process, the outer preform molding process and the main heating curing process. The inner shell preform having the inner shell preform and the outer shell preform formed on the outer periphery of the inner shell preform as a core are reliably integrated and cured. As a result, a strong FRP hollow structure having a beam structure inside is reliably formed using the inner shell preform as a structural member. The inner shell preform as the core contributes to improvement in strength and rigidity as a structural member of the FRP hollow structure.

  On the other hand, the core according to the present invention is a core used in a method for forming an FRP hollow structure having a beam structure therein, and a plurality of parts formed by laminating a prepreg on a tool having a predetermined shape. It consists of a core preform having a beam structure in which a preform is assembled, and this core preform is cured by preheating to a curing depth of 5 to 15%.

  The core according to the present invention is configured by curing a core preform to a curing depth of 5 to 15% by preheating, and has a high dimensional accuracy due to an increase in surface hardness. Therefore, a prepreg is laminated on the outer periphery. Thus, in the FRP hollow structure forming method for forming the outer preform, it functions reliably as a core for forming the outer preform. In addition, the core cured to a curing depth of 5 to 15% in this way is softened and fluidized by reheating, and thus exhibits adhesiveness. Therefore, the core is heated together with the outer preform formed on the outer periphery thereof. As a result, it is firmly bonded to the outer preform and reliably integrated, and contributes to improvement in strength and rigidity as a structural member of a strong FRP hollow structure having a beam structure inside.

  The “prepreg” used in the FRP hollow structure molding method of the present invention and the core used in this molding method is a sheet-like intermediate material in which reinforcing fibers are impregnated with a thermosetting resin. is there. Examples of the reinforcing fibers include inorganic fibers such as carbon fibers, glass fibers, and aramid fibers, and various metal fibers. Examples of the thermosetting resin include an epoxy resin, a polyester resin, a silicone resin, and a polyimide resin.

  According to the FRP hollow structure forming method according to the present invention, the inner shell preform having a beam structure and the outer preform formed on the outer periphery of the inner shell preform as a core are reliably integrated. Since it can be cured, a strong FRP hollow structure having a beam structure inside can be reliably formed using the inner shell preform as a structural member. Further, since the inner shell preform as the core serves as a structural member of the FRP hollow structure, a conventional core removal step is not required, and the number of steps for forming the FRP hollow structure can be reduced.

  On the other hand, since the core according to the present invention has high dimensional accuracy due to the increase in surface hardness, the outer preform is molded in the FRP hollow structure molding method in which the outer preform is formed by laminating the prepreg on the outer periphery. The function as a core for doing this can be demonstrated reliably. In addition, since the core softens and fluidizes due to reheating and the adhesiveness is developed, this core adheres well to the outer preform by being heated together with the outer preform formed on the outer periphery thereof. As a structural member of a strong FRP hollow structure having a beam structure inside, it can contribute to the improvement of strength and rigidity.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a method for forming an FRP structure according to the present invention and a core used in the molding method will be described below with reference to the drawings. In the drawings to be referred to, FIG. 1 is a perspective view showing a structure of an FRP hollow structure formed by a forming method according to an embodiment, and FIG. 2 is a view for forming the FRP hollow structure by a forming method according to an embodiment. FIG.

  The FRP hollow structure forming method according to an embodiment is a method of forming the FRP hollow structure 1 as shown in FIG. 1, and includes a parts preform forming step A and an inner shell preform assembling step shown in FIG. 2. The FRP hollow structure 1 shown in FIG. 1 is formed by passing through B, the pre-heat curing step C, the outer preform forming step D, and the main heat curing step E.

  The FRP hollow structure 1 includes a rectangular tube-shaped inner shell preform 2 in which beam structures 2A and 2B having a groove-shaped cross section (a U-shaped cross section or a U-shaped cross section) are formed to face left and right wall surfaces (FIG. 3). And the outer preform 3 formed on the outer periphery of the inner shell preform 2 are cured by heat treatment and integrally bonded to form a rectangular tube having a beam structure inside.

  Here, in the part preform molding step A (see FIG. 2), each of the part preforms 2A to 2F obtained by dividing the inner shell preform 2 shown in FIG. 3 into, for example, six parts as shown in FIG. To do. That is, the parts preforms 2A and 2B corresponding to the beam-shaped portions 2A and 2B having a groove-shaped cross section, and a shape having a notch into which the part preforms 2A and 2B are fitted, are divided into two vertically and a notch Each of the part preforms 2C to 2F divided into two parts at the front and rear is formed.

  The part preforms 2A and 2B are each formed into a hat-shaped cross-sectional shape in which joining margins are continuous before and after the groove-shaped cross-section by laminating prepregs cut into a rectangle on the outer periphery of a dedicated tool (not shown). That is, the part preform 2A is formed into a hat-shaped cross-sectional shape in which the joining allowances 2A1, 2A2 are continuous in the front and back, and the part preform 2B is formed in a hat-shaped cross-sectional shape in which the joining allowances 2B1, 2B2 are continuous in the front and rear. To do.

  On the other hand, the part preforms 2C to 2F are outer peripheries of a dedicated tool (not shown) obtained by cutting a prepreg cut into a substantially rectangular shape having protrusions 2C1 to 2F1 corresponding to notches into which the part preforms 2A and 2B are fitted. To form a U-shaped cross-sectional shape.

  The prepreg used for molding each of the part preforms 2A to 2F is a sheet-shaped intermediate material in which a reinforcing fiber is impregnated with a thermosetting resin. For example, a carbon / epoxy prepreg in which a carbon fiber is impregnated with an epoxy resin (For example, W3101 / Q-112J manufactured by Toho Tenax Co., Ltd.) is used. And this prepreg is laminated | stacked on 11 layers, for example, and each part preform 2A-2F is shape | molded.

  In the inner shell preform assembling step B (see FIG. 2), the respective part preforms 2A to 2F formed into the shape shown in FIG. 4 are assembled as the inner shell preform 2 having the shape shown in FIG. At that time, the joining margin 2A1 on the front side of the parts preform 2A is overlapped on one side surface on the rear side from which the projecting pieces 2C1 and 2D1 of the parts preforms 2C and 2D protrude, and the joining margin 2A2 on the rear side is the parts preform. The 2E, 2F protrusions 2E1, 2F1 are overlapped on one side of the front side where the protrusions 2E1, 2F protrude. Further, the joint margin 2B1 on the front side of the parts preform 2B is overlapped with the other side surface on the rear side from which the projecting pieces 2C1 and 2D1 of the part preforms 2C and 2D protrude, and the joint margin 2B2 on the rear side is composed of the parts preform 2E. , 2F are overlapped with the other side surface on the front side from which the protruding pieces 2E1, 2F1 protrude.

  In the preheating and curing step C (see FIG. 2), the inner shell preform 2 assembled into the shape shown in FIG. 3 is preheated in a heating furnace (not shown) to 5 to 15% (preferably 5 to 10%). Cure to cure index. At that time, the preheating temperature of the inner shell preform 2 is set to a temperature of 70 to 80 ° C. which is at least about 50 ° C. lower than 120 to 130 ° C. recommended as a curing temperature of the carbon / epoxy prepreg.

  Further, the curing depth of the inner shell preform 2 is determined based on a detection signal of a dielectric property sensor attached to the surface of the inner shell preform 2. Then, when the detection signal value of the dielectric property sensor reaches a value obtained in advance as a value corresponding to a curing depth of 5 to 15% (preferably 5 to 10%), the inner shell preform 2 is cooled. The curing reaction is stopped.

A specific example of this pre-heating and curing step C is described as follows. A dielectric property sensor (IDEX-Midcon manufactured by NETZSCH-Geratebau) is attached to the surface of the inner shell preform 2 (see FIG. 3). The shell preform 2 is put into a heating furnace together with a thermocouple, and 80 ° C./0.0. Preheating was performed in a heated and pressurized atmosphere of 2 atm. Then, the resin temperature, resin viscosity, and cure depth (Cure Index) of the inner shell preform 2 were measured using a microdielectrometer (Eumetric system III manufactured by NETZSCH-Geratebau) as a measurement system.

  Prior to the measurement of the cure index by the measurement system, an experiment was performed in which a test piece equivalent to the inner shell preform 2 was rapidly heated and gradually cooled to be cured 100%. The measurement parameters were extracted from the data obtained in (1). And in the measurement of the cure depth (Cure Index) by a measurement system, the cure depth (Cure Index) was correct | amended based on the measurement parameter previously extracted by the measurement system.

  When the measurement result of the cure depth (Cure Index) by the measurement system reaches 10%, the heating of the inner shell preform 2 by the heating furnace is stopped, and the inner shell preform 2 is rapidly cooled to stop the curing reaction. I let you. The elapsed time of the preheating treatment in the heating furnace was 80 minutes, and the temperature reached by the resin of the inner shell preform 2 was 84 ° C. (see FIG. 5).

  The inner shell preform 2 molded through the preheating and curing step C is cured to a cure index of 10% and has a high dimensional accuracy due to an increase in surface hardness. It functions reliably as a core when the outer preform 3 is molded by the preform molding step D (see FIG. 2).

  Therefore, in the outer preform forming step D, for example, the inner shell preform 2 cured to a cure depth of 10% in the preheating and curing step C is used as a core, and a belt-like prepreg is formed on the outer periphery thereof with, for example, 12 layers. The outer preform 3 is formed by winding in a laminated state (see FIG. 6). The prepreg used is the same carbon / epoxy prepreg (for example, W3101 / Q-112J manufactured by Toho Tenax Co., Ltd.) as the prepreg used for forming the inner shell preform 2.

  In the main heat curing step E (see FIG. 2), the outer preform 3 laminated on the outer periphery of the inner shell preform 2 is finally heated and cured in the mold together with the inner shell preform 2. That is, the outer preform 3 laminated on the outer periphery of the inner shell preform 2 is put into an FRP mold 4 having an upper and lower split structure as shown by a two-dot chain line in FIG. This is heated for 4 hours in a heated and pressurized atmosphere of 4 atm.

  In such a main heating and curing step E, the inner shell preform 2 that has been cured to a curing depth of 10% in advance is softened and fluidized at the initial stage of the main heating time, and exhibits adhesiveness. It adheres well to the inner surface of the preform 3 and is reliably integrated. Thereafter, as the main heating time elapses, the inner shell preform 2 and the outer preform 3 are integrally cured.

  Therefore, according to the FRP hollow structure forming method according to the embodiment, as shown in FIG. 1, the strong FRP hollow structure 1 having the beam structures 2A and 2B inside can be reliably formed. . The inner shell preform 2 as a core for forming the outer preform 3 contributes to improvement in strength and rigidity as a structural member of the FRP hollow structure 1 as it is, and therefore, a core removal step is not required. The number of molding steps for the FRP hollow structure 1 can be reduced.

  The molding method of the FRP hollow structure according to the present invention is not limited to the above-described embodiment. For example, in the outer preform forming step D (see FIG. 2), as shown in FIG. 8, appropriate foam materials 5 and 5 serving as cores in the respective concave portions of the beam structure portions 2A and 2B of the inner shell preform 2 are formed. May be formed by stacking the outer preform 3 on the outer periphery thereof.

  Moreover, in the preheating curing process C (refer FIG. 2), when the measurement result of the cure depth (Cure Index) by the measurement system mentioned above reached arbitrary values in the range of 5 to 15% by the following experimental results. The heating of the inner shell preform 2 by the heating furnace may be stopped.

  FIG. 9 shows changes in resin viscosity due to reheating of the inner shell preform 2 using the inner shell preform 2 having a curing depth of 5% and the inner shell preform 2 having a curing depth of 15% as samples. The experimental results are shown. In this experiment, the two inner shell preforms 2 as samples were held at room temperature for 5 days, and then the inner shell preforms 2 were heated at 130 ° C./4 atm as in the above-described heat curing step E. Reheated in a pressurized atmosphere for 4 hours.

  Here, as shown in the graph of the experimental results in FIG. 9, the inner shell preform 2 having a curing depth of 5% has a resin viscosity that is greatly reduced by reheating (shown by a solid line graph in the figure). The adhesiveness increased and good tackiness (tackiness) was expressed. On the other hand, the inner shell preform 2 with a cure depth of 15% has a smaller decrease in resin viscosity due to reheating than the inner shell preform 2 with a cure depth of 5% (in the graph of the broken line in the figure). As shown in the figure, the fluidity is low, but it still exhibits slight tackiness (tackiness). From this experimental result, it was found that the inner shell preform 2 having a curing depth exceeding 15% cannot exhibit tackiness (tackiness) but exhibits tackiness (tackiness) at a curing depth of 15% or less. .

It is a perspective view which shows the structure of the FRP hollow structure shape | molded by the shaping | molding method which concerns on one Embodiment of this invention. It is a work process figure for shape | molding a FRP hollow structure by the shaping | molding method which concerns on one Embodiment. FIG. 3 is a perspective view showing the structure of the inner shell preform assembled by the inner shell preform assembling step of FIG. 2. FIG. 4 is a perspective view of each part preform obtained by dividing the inner shell preform shown in FIG. 3 into six parts. It is a graph which shows the relationship between the preheating temperature of the inner shell preform shown in FIG. 3, and the hardening depth of resin of an inner shell preform. FIG. 3 is a perspective view showing the outer preform formed by the outer preform forming step of FIG. 2 together with the inner shell preform. It is a perspective view which shows the FRP type | mold used for this heat curing process of FIG. 2 with an inner shell preform and an outer shell preform. It is a perspective view which shows the modification of the core used in the outline preform shaping | molding process of FIG. It is a graph which shows the change of the resin viscosity by the reheating experiment of two inner shell preforms from which the hardening depth similar to the inner shell preform shown in FIG. 3 differs.

Explanation of symbols

1 FRP hollow structure 2 Inner shell preform 2A Beam structure (part preform)
2B Beam structure (part preform)
2C-2F Parts preform 3 Outer preform 4 FRP type 5 Foam material A Parts preform molding process B Inner shell preform assembly process C Preheating curing process D Outer preform molding process E Main heating curing process

Claims (2)

A method for forming an FRP hollow structure having a beam structure therein,
A part preform molding process for molding a part preform of each part of the inner shell preform having a beam structure by laminating a prepreg on a tool of a predetermined shape,
An inner shell preform assembling step for assembling each molded part preform as the inner shell preform;
A preheating and curing step in which the assembled inner shell preform is preheated and cured to a predetermined curing depth;
An outer preform molding step for forming an outer preform by laminating a prepreg on the outer periphery of the preheated inner shell preform as a core,
A main heating and curing step of curing the outer preform together with the inner shell preform by heating in a mold.
In the preliminary heating and curing step, the inner shell preform is cured to a curing depth of 5 to 15%. A core used in a method for forming an FRP hollow structure having a beam structure therein,
Each consists of a core preform having a beam structure in which a plurality of part preforms formed by laminating prepregs on a tool of a predetermined shape are assembled,
A core formed by curing the core preform to a curing depth of 5 to 15% by preheating.

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