Patent Description:
Document <CIT> teaches a conventional method and plant for consolidating fiber composite structures. Disclosed therein is a method for consolidating a fiber composite structure with at least one thermoplastic or thermoelastic polymer, wherein the fiber composite structure is firstly placed between a plate-shaped base and a plate-shaped cover, wherein the cover and base are sealed by a sealing element, wherein the cover is displaceable in relation to the base, wherein, by generating a negative pressure between cover and base, the cover is pushed against the base so as to clamp the fiber composite structure between the cover and the base; then, performing a heating step of the fiber composite structure by electromagnetic radiation; afterwards, performing a cooling step for cooling the fiber composite structure and removing the consolidated fiber composite structure.

In order to meet the requirements of various applications, the research of material technology has been rapidly developed. However, the requirements of material properties are tending to be severe as the developments of the applications. Accordingly, composite materials that blend various materials to combine properties of the materials are vigorously developed. Because carbon fiber materials have light weight and good mechanical properties (such as strength, modulus and like), they are often used as a reinforcing material for the composite materials.

The composite materials generally are formed by liquid molding methods (such as resin transfer molding (RTM), vacuum-assisted RTM, resin infusion (RI) or the like), pressure molding methods (such as a hot pressing apparatus), spraying, hand and spray lay-up, autoclave molding and the like. The molding with the hot pressing apparatus has higher operational convenience and efficiency, and the composite material produced by the autoclave molding has better properties and quality.

However, a mold is used in the molding with the hot pressing apparatus to adjust dimensions of the composite material, and therefore there is a need to enlarge the mold as an enlargement of the dimensions of the composite material. The enlarged mold is heavier, thus lowering convenience of the process. Furthermore, it is necessary to replace the mold when the composite materials with different specifications are to be produced, thereby increasing risks for operators to move the mold. The equipment for the autoclave molding is more complicated, and therefore racing and lowering for temperature of the equipment takes more time, thereby increasing cost of the composite materials. Besides, autoclave molding is applied to produce the composite materials under parameters of high temperature and high pressure, such that the system has higher instability and higher environmental risk.

Accordingly, there is an urgent need to provide a method for molding the composite material for improving the defects that the conventional molding process is not conveniently applicable to fabricate the composite materials with various dimensions.

Therefore, an aspect of the present application is to provide a method for molding a composite material. The method can conveniently produce composite materials with various thicknesses by disposing a plate element and a dimension control element.

According to an aspect of the present application, a method for molding a composite material according to claim <NUM> is provided. In this molding method, a component to be pressed is firstly placed in a gas-isolation element and between an upper pressing plate and a lower pressing plate. The component to be pressed includes a prepreg element, a sealing element and at least one dimension control element. In a plane perpendicular to the pressing direction, the sealing element surrounds the prepreg element. The sealing element has a discharge channel. The sealing element is disposed between the prepreg element and the dimension control element. Then, corresponding to a position of the prepreg element, a plate element is placed between the gas-isolation element and the upper pressing plate. And then, a hot pressing step is performed by the upper pressing plate and the lower pressing plate. After the hot pressing step is performed, a cooling step is performed to produce the composite material.

The sealing element is a material that can be compressively deformed by pressure and a height of the aforementioned sealing element is not lower than a height of the prepreg element. Furthermore, each dimension control element is a component that is not deformed under pressure.

According to some embodiments of the present application, a width of the aforementioned discharge channel is <NUM> to <NUM>.

According to some embodiments of the present application, the discharge channel penetrates the sealing element along a direction perpendicular to the aforementioned pressing direction.

According to some embodiments of the present application, a number of the aforementioned dimension control elements is even, and each of the dimension control elements is disposed opposite to another.

According to some embodiments of the present application, a height of each of the aforementioned dimension control elements is equal to the sum of heights of the composite material and the plate element.

According to some embodiments of the present application, along the aforementioned pressing direction, a projection area of the prepreg element completely falls within a projection area of the plate element.

According to some embodiments of the present application, along the aforementioned pressing direction, a projection area of the component to be pressed is located in a pressing area of the upper pressing plate.

According to some embodiments of the present application, a surface roughness of the aforementioned upper pressing plate, the lower pressing plate and the plate element is <NUM> to <NUM>.

According to some embodiments of the present application, before the aforementioned operation of performing the hot pressing step, the method selectively comprises an operation of performing a gas bleeding step to extract a gas in the gas-isolation element.

According to some embodiments of the present application, the composite material produced by the aforementioned molding method, has a porosity being not greater than <NUM>%.

According to some embodiments of the present application, a projection area of the plate element and a projection area of the sealing element are not overlapped along the pressing direction. As afore-mentioned, the discharge channel may penetrate the sealing element along a direction perpendicular to the pressing direction.

As afore-mentioned, a projection area of the component to be pressed may be located in a pressing area of the upper pressing plate along the pressing direction.

Before the aforementioned operation of performing the hot pressing step, the method may selectively comprise an operation of performing a gas bleeding step to extract a gas in the gas-isolation element.

The aforementioned sealing element can be deformed during the hot pressing step, and thereby the discharge channel is closed.

The aforementioned cooling step can be performed under a situation that a pressure applied by the upper pressing plate is maintained.

In the method for molding a composite material of the present application, dimensions of the composite material can be conveniently controlled by disposing the dimension control elements and the plate element, thereby meeting requirements. Moreover, in order to meet requirements of mechanical properties, the component to be pressed includes the sealing element surrounding the prepreg element, such that an outflow rate of a resin material can be efficiently controlled during the hot pressing step. Accordingly, the manufacturing method of the present application can effectively produce the composite material giving consideration to dimensional requirements and mechanical properties. Controlling dimensions of the composite material can be conveniently achieved by adjusting the dimension control element and/or the plate element, and therefore a hot pressing apparatus can be applied to produce composite materials with different specifications, and it is unnecessary to perform additional modifications.

The invention can be more fully understood by reading the following detailed description of the embodiments, with reference made to the accompanying drawings as follows:.

Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

Referring to <FIG>, it illustrates a flow chart of a method for molding a composite material according to the present invention. In the method <NUM>, a component to be pressed is firstly placed in a gas-isolation element, and the component to be pressed is disposed between an upper pressing plate and a lower pressing plate, shown as operation <NUM>.

Referring to <FIG>, it illustrates a three-dimensional view of a component to be pressed in a method according to an embodiment of the invention. The component to be pressed 200a includes a prepreg element <NUM>, a sealing element <NUM> and dimension control elements 231a and 233a. In the x-y plane, the sealing element <NUM> surrounds the prepreg element <NUM>, and the sealing element <NUM> is disposed between the prepreg element <NUM> and the dimension control elements 231a and 233a. The sealing element <NUM> has a discharge channel 221a.

The prepreg element <NUM> may be fiber materials which have been impregnated with a resin material. The prepreg element <NUM> may be, for example, a stack formed of multiple layers of fiber cloths which have been impregnated with the resin material. In some examples, the fiber materials can include but be not limited to rayon materials, natural fiber materials and/or other suitable fiber materials, and the resin material can include but be not limited to epoxy resin, vinyl ester resin (VE), bismaleimide (BMI), phenolic resin and/or other suitable thermosetting resin materials. For example, the fiber materials can be carbon fiber materials, and the fiber materials may be unidirectional (UD) fibers and woven fabrics (e.g. <NUM>, <NUM>, <NUM>, <NUM> and <NUM> woven fabrics).

The sealing element <NUM> is a material that can be compressively deformed by pressure. There are not limitations to the shape of the sealing element <NUM> as long as the prepreg element <NUM> can be surrounded by the sealing element <NUM>. As shown in <FIG>, although a projection shape of the prepreg element <NUM> on the x-y plane is a quadrilateral, and the sealing element <NUM> is a square frame, the present application is not limited to this. The projection shape of the prepreg element <NUM> on the x-y plane can be any shapes to meet requirements of applications, but the sealing element <NUM> can still be a square frame, or the sealing element <NUM> can be a frame body that can change with the shape of the prepreg element <NUM>.

There are no specific limitations to the location of the discharge channel 221a of the sealing element <NUM> as long as it can penetrate the sealing element <NUM> to allow excess materials extruded in the subsequent hot pressing step to be discharged. In some embodiments, width W of the discharge channel 221a may be <NUM> to <NUM>, and preferably be <NUM> to <NUM>. When the width of the discharge channel 221a is within the aforementioned range, the aforementioned excess materials can be easily discharged. In <FIG>, the sealing element <NUM> is not a continuous frame due to the disposition of the discharge channel 221a, but the present application is not limited thereto. In other embodiments, referring to <FIG>, and they respectively illustrate a side view of a sealing element used in some embodiments of the present invention. The discharge channel 221b of the sealing element <NUM> can be a circular channel (as shown in <FIG>), or the discharge channel 221c is a groove structure disposed on a bottom surface of a side wall of the sealing element <NUM> (as shown in <FIG>). In some embodiments, in order to obtain a better discharging effect, and further the sealing element <NUM> will be deformed under pressure, such that a distance between the sealing element <NUM> and the prepreg element <NUM> can be <NUM> to <NUM>, and preferably be <NUM> to <NUM>.

Referring to <FIG>. The dimension control elements 231a and 233a are both components that are not deformed under pressure. It is noted that the components that are not deformed under pressure means that dimensions of the components will not vary under the pressure applied during the following hot pressing step. In some examples, the dimension control elements 231a and 233a are formed from metal materials, polymer materials, and/or other suitable materials. In some examples, corresponding to the dimensions of the composite material to be produced, a deviation of dimensions of the dimension control elements 231a and 233a is controlled to be not greater than <NUM>. It is easily to control the dimensions of the composite materials with the disposition of the dimension control elements 231a and 233a when the following hot pressing step is performed. The component to be pressed 200a can selectively include other additional dimension control elements except the dimension control elements 231a and 233a. However, a number of the other additional dimension control elements is even for better hot pressing effect, and each of the dimension control elements and another one are disposed on opposite sides of the prepreg element <NUM>, for example, the arrangement of the dimension control elements 231a and 233a. Similarly, a distance between the sealing element <NUM> and the dimension control elements 231a and 233a may be <NUM> to <NUM>, and preferably be <NUM> to <NUM>.

In the z-axis direction, a height of the sealing element <NUM> is not lower than a height of the prepreg element <NUM>. Preferably, the height of the sealing element <NUM> is higher than the height of the prepreg element <NUM>. Further, the height of the sealing element <NUM> is higher than the heights of the dimension control elements 231a and 233a.

Referring to <FIG>, and it illustrates a three-dimensional view of a component to be pressed in a method according to an embodiment of the invention. The component to be pressed 200b is substantially similar to the component to be pressed 200a in configuration, but the difference therebetween resides in that the component to be pressed 200b includes a dimension control element 230b, and the dimension control element 230b surrounds the sealing element <NUM>.

Referring to <FIG>, <FIG> and <FIG> simultaneously, and <FIG> illustrates a cross-sectional view of a hot pressing apparatus before a hot pressing step is performed according an embodiment of the invention. During the operation <NUM>, the component to be pressed 200a is placed in the gas-isolation element <NUM> and disposed between the upper pressing plate 320a and the lower pressing plate 320b. There are not specific limitations to materials of the gas-isolation element <NUM> as long as it can efficiently block the gas and not be broken during the following hot pressing step. In some examples, the gas-isolation element <NUM> can be a vacuum bag. When the component to be pressed 200a is placed in the gas-isolation element <NUM>, the gas-isolation element <NUM> flatly and directly contacts a top surface and a bottom surface of the prepreg element <NUM> for preventing the composite materials from having lined surface, and the gas-isolation element <NUM> also flatly and directly contacts top surfaces and bottom surfaces of the sealing element <NUM> and the dimension control elements 231a and 233a for enhancing hot pressing effect. A projection area of the component to be pressed 200a projected along the z-axis direction (i.e. a pressing direction 300a of the hot pressing step) is within a pressing area of the upper pressing plate 320a for improving pressing effect of the following hot pressing step.

After the operation <NUM> is performed, the plate element <NUM> is placed corresponding to a position of the prepreg element <NUM>, shown as operation <NUM>. A projection area of the prepreg element <NUM> projected along the pressing direction 300a is completely within a projection area of the plate element <NUM> to obtain better hot pressing effect. In other words, the upper surface of the prepreg element <NUM> is completely covered by the plate element <NUM>. Preferably, the plate element <NUM> has a projection area corresponding to the prepreg element <NUM> along the pressing direction 300a. The projection area of the sealing element <NUM> and the projection area of the plate element <NUM> are not overlapped along the pressing direction 300a to avoid that the dimensions of the composite materials cannot meet the requirements. The bottom surface of the plate element <NUM> and the top surface of the lower pressing plate 320b can selectively have surface undulations to subject the composite materials to include a non-planar surface profile corresponding to the surface undulations, and/or an additional component is disposed on the top surface of the lower pressing plate 320b to subject the composite materials to include a non-planar surface profile. However, it should be noted that the dimensional requirements of the composite materials are also be considered when the additional component is disposed.

Before the following hot pressing step is performed, a height H<NUM> of the prepreg element <NUM> is lower than a height H<NUM> of the sealing element <NUM>, the height H<NUM> of the sealing element <NUM> is higher than heights H<NUM> of the dimension control elements 231a and 233a, and the sealing element <NUM> without being deformed by compression has a width W<NUM>. In order to allow the sealing element <NUM> to be deformed during the hot pressing step, there can be a space 220a between the sealing element <NUM> and the prepreg element <NUM>, and there is also a space 220b between the sealing element <NUM> and the dimension control elements 231a and 233a.

In some embodiments, after the operation <NUM> is performed, a gas bleeding step is selectively performed to extract the gas in the gas-isolation element <NUM>, and thereby flatness of the prepreg element <NUM>, the sealing element <NUM> and the dimension control elements 231a and 233a resulted from the gas-isolation element <NUM> is improved. Simultaneously, a portion of the excess resin materials in the prepreg element <NUM> can be discharged through the discharge channel 221a (shown in <FIG>) of the sealing element <NUM>.

Referring to <FIG>, <FIG> and <FIG> simultaneously, and <FIG> illustrates a cross-sectional view of the hot pressing apparatus after the hot pressing step is performed according to an embodiment of the invention. After the operation <NUM> is performed, the hot pressing step and the cooling step are performed to produce the composite material <NUM>, shown as operations <NUM> to <NUM>. When the hot pressing step is performed, the upper pressing plate 320a is pressed down along the pressing direction 300a, and the prepreg element <NUM> is pressed down by the plate element <NUM> until the upper pressing plate 320a pressed against the dimension control elements 231a and 233a, and thereby the uncooled composite material <NUM> is obtained. In some embodiments, a surface roughness of the upper pressing plate 320a, the lower pressing plate 320b and the plate element <NUM> is <NUM> to <NUM> for improving surface quality of the composite material <NUM>, and preferably the surface roughness thereof is <NUM> to <NUM>. In some examples, the upper pressing plate 320a and the lower pressing plate 320b can be formed from SKD series, SUS series and/or SCM series steel, and the plate element <NUM> can be formed from aluminum metal. High temperature heat energy applied in the hot pressing step can subject the resin materials in the prepreg element <NUM> to have fluidity, and therefore the excess resin materials can be discharged through the discharge channel 221a (shown in <FIG>) of the sealing element <NUM> as the lowering of the upper pressing plate 320a, and further air bubbles in the materials are brought out with the flowing of the resin materials, thereby reducing pores in the composite materials <NUM> and enhancing quality thereof. Because the excess resin materials and the pores can be eliminated, it is unnecessary to use high-pressure gas in the method of the present application, and the obtained composite material <NUM> can have better surface quality and mechanical properties to meet the requirements of the application without further performing a processing step.

Before and during the hot pressing step is performed, the height H<NUM> of the prepreg element <NUM> is lower than the initial height H<NUM> of the sealing element <NUM>, and thus the resin materials merely flow out from the discharge channel 221a rather than other positions. Accordingly, a total outflow rate of the materials can be easily adjusted, and thereby properties of the composite materials <NUM> are controlled.

Further, the pressure applied by the upper pressing plate 320a also causes the sealing element <NUM> to be deformed, and therefore the compressed sealing element <NUM> has a lower height H<NUM> and a wider width W<NUM>. Because the prepreg element <NUM> and the dimension control elements 231a and 233a are fixed, the space 220a and the space 220b are both reduced as the deformation of the sealing element <NUM> to compared with those before the hot pressing step is performed. Based on the compression deformation of the sealing element <NUM>, the discharge channel 221a (<FIG>) will also be closed due to the deformation, such that the resin materials with fluidity will not further flow out, thereby maintaining the quality and mechanical properties of the composite material <NUM>. In some examples, the total outflow rate of the aforementioned resin materials is not greater than <NUM>% in the method <NUM> of the present application. When the total outflow rate of the resin materials is not greater than <NUM>%, the composite material <NUM> has more suitable fiber content, and thereby dimensions and mechanical properties required in the application can simultaneously be met.

When the upper pressing plate 320a is pressed against the dimension control elements 231a and 233a, the upper pressing plate 320a cannot be further pressed down, and therefore a difference between the height H<NUM> of the dimension control elements 231a and 233a and the height H<NUM> of the plate element <NUM> is the height H<NUM> of the obtained composite material <NUM>. In other words, the composite materials with various dimensions can be conveniently produced with the method <NUM> of the present application by adjusting the height H<NUM> of the plate element <NUM>.

The aforementioned cooling step is performed to cool the uncooled composite material <NUM> to <NUM> under a situation that the pressure applied by the upper pressing plate 320a is maintained, and further a demolding step is performed to obtain the composite material. In some examples, the composite material <NUM> manufactured by the present application contains <NUM>% to <NUM>% of fiber materials, and its porosity is not greater than <NUM> %. The coefficient of variation (CV) of mechanical properties of the composite material <NUM> is not more than <NUM>%. When the composite material <NUM> contains <NUM>% of the fiber materials, tensile strength of the composite material <NUM> with a general modulus (<NUM> msi) is not less than <NUM> MPa, and tensile strength of the composite material with an intermediate modulus (<NUM> msi) is not less than <NUM> MPa, in these examples.

A <NUM> woven prepreg and a UD fiber prepreg made of vinyl resin were laminated to obtain a stack. Then, the component to be pressed containing the stack, a sealing rubber strip and two dimension control sheets was placed in a vacuum bag, and the component to be pressed was placed on a central area of the mirror-surface pressing iron plate. The dimension control sheets were respectively placed on opposite sides of the stack and on the corresponding two sides, and the sealing rubber strip was located between the stack and the dimension control sheets. Moreover, a distance between the sealing rubber strip and the stack and a distance between the sealing rubber strip and the adjacent dimension control sheet can be independently <NUM> to <NUM>. Next, the gas in the vacuum bag was bled, such that the vacuum bag was flatly on the component to be pressed. An aluminum plate was placed corresponding to a position of the stack, and a hot pressing step was performed by the two mirror-surface pressing iron plate in a vacuum state based on curing properties of a resin material. After the hot pressing step was performed, the pressurized state of the mirror-surface pressing iron plates was maintained, and a cooling step was performed to cool to less than or equal to <NUM>. After demolding, the composite material of Preparation Embodiment <NUM> can be obtained.

Preparation Embodiment <NUM> to Preparation Embodiment <NUM> were practiced with the same method as in Preparation Embodiment <NUM> by using various resin materials and kinds of the prepreg. The stack of Preparation Embodiment <NUM> was formed from <NUM> woven prepreg and the UD fiber prepreg, and the prepreg both were made of epoxy resin. The stack of Preparation Embodiment <NUM> was obtained by laminating UD fiber prepreg with multi-angles (such as the angle was <NUM>°, <NUM>°, +<NUM>°and -<NUM>°), and the UD fiber prepreg was made of epoxy resin. The stack of Preparation Embodiment <NUM> was obtained by laminating UD fiber prepreg with a single angle, and the UD fiber prepreg was made of epoxy resin.

The method for producing the composite material (glass transition temperature was <NUM>) of Preparation Embodiment <NUM> was adopted by Embodiment <NUM>. During the hot pressing step, temperature was <NUM>, pressure was <NUM>, and pressing period was <NUM> minutes. The obtained composite material was further subjected to evaluation methods of mechanical properties such as tensile, bending and compression, and coefficients of variation of the evaluation results all were controlled to be not more than <NUM>%. Besides, porosity of the composite material was <NUM>%.

The method for producing the composite material (glass transition temperature was <NUM>) of Preparation Embodiment <NUM> was adopted by Embodiment <NUM>. During the hot pressing step, temperature was <NUM>, pressure was <NUM>, and pressing period was <NUM> minutes. Coefficients of variation of the mechanical properties such as tensile, bending and compression of the composite material all were controlled to be not more than <NUM>%, and porosity of the composite material was <NUM>%.

The method for producing the composite material (glass transition temperature was <NUM>) of Preparation Embodiment <NUM> was adopted by Embodiment <NUM>. During the hot pressing step, temperature was <NUM>, pressure was <NUM>, and pressing period was <NUM> minutes. The obtained composite material was further subjected to evaluation methods of mechanical properties such as unnotched tension and compression. Coefficients of variation thereof both were controlled to be not more than <NUM>%, and porosity of the composite material was <NUM>%.

The method for producing the composite material (glass transition temperature was <NUM>) of Preparation Embodiment <NUM> was adopted by Embodiment <NUM>. During the hot pressing step, temperature was <NUM>, pressure was <NUM>, and pressing period was <NUM> minutes. The obtained composite material was further subjected to an evaluation method of open hole compression test. A coefficient of variation thereof was controlled to be not more than <NUM>%, and porosity of the composite material was <NUM>%.

The method for producing the composite material (glass transition temperature was <NUM>) of Preparation Embodiment <NUM> was adopted by Embodiment <NUM>. During the hot pressing step, temperature was <NUM>, pressure was <NUM>, and pressing period was <NUM> minutes. Coefficients of variation of the mechanical properties such as tensile, bending and short-beam of the obtained composite material all were controlled to be not more than <NUM>%, and porosity of the composite material was <NUM>%. The measurement of the short-beam mechanical property was evaluated with a standard method of American Society for Testing and Materials (ASTM) No. D2344.

The method for producing the composite material (glass transition temperature was <NUM>) of Preparation Embodiment <NUM> was adopted by Embodiment <NUM>. During the hot pressing step, temperature was <NUM>, pressure was <NUM>, and pressing period was <NUM> minutes. Coefficients of variation of the mechanical properties such as tensile, bending and short-beam of the obtained composite material all were controlled to be not more than <NUM>%, and porosity of the composite material was <NUM>%.

Claim 1:
A method for molding a composite material, comprising:
placing a component to be pressed (200a) in a gas-isolation element (<NUM>) and between an upper pressing plate (320a) and a lower pressing plate (320b), wherein the component to be pressed (200a) includes:
a prepreg element (<NUM>);
a sealing element (<NUM>), which is a material that can be compressively deformed by pressure; wherein, in z-axis direction, a height (H<NUM>) of the sealing element (<NUM>) is not lower than a height (H<NUM>) of the prepreg element (<NUM>); and
at least one dimension control element (231a and 233a), wherein each dimension control element (231a and 233a) is a component that is not deformed under pressure; wherein a height (H<NUM>) of the sealing element (<NUM>) is higher than a height (H<NUM>) of the at least one dimension control element (231a and 233a); and
in a plane perpendicular to a pressing direction (300a), the sealing element (<NUM>) surrounds the prepreg element (<NUM>), the sealing element (<NUM>) has a discharge channel (221a), and the sealing element (<NUM>) is disposed between the prepreg element (<NUM>) and the at least one dimension control element (231a and 233a);
corresponding to a position of the prepreg element (<NUM>), placing a plate element (<NUM>) between the gas-isolation element (<NUM>) and the upper pressing plate (320a);
performing a hot pressing step by the upper pressing plate (320a) and the lower pressing plate (320b); and
performing a cooling step to produce the composite material (<NUM>).