CN110328834A - A kind of forming and machining method of crystallinity CFRTP - Google Patents

Abstract

The invention provides a forming and processing method of crystalline CFRTP, which belongs to the field of composite material processing and forming. The forming processing method includes: heating the CFRTP until the CFRTP is in a completely molten state, putting the CFRTP into a cooling medium, and performing quenching treatment; heating the cooled CFRTP until the CFRTP is in a rubber state, and then starting to perform forming treatment on the CFRTP, and Continue to heat the CFRTP, complete the forming process to the CFRTP before the CFRTP is completely melted; and continue to heat the formed CFRTP to a completely melted state, then cool naturally. This forming processing method can realize the separation of CFRTP preparation and forming, which is conducive to the implementation of standardization; and in this method, the forming temperature is below the complete melting temperature of the resin, which effectively avoids the problem of fiber bundle flow caused by resin flow, and improves the stability of CFRTP after forming. mechanical properties.

Description

A kind of forming processing method of crystalline CFRTP

technical field

The invention relates to the field of composite material processing, in particular to a forming and processing method of crystalline CFRTP.

Background technique

CFRTP, for continuous fiber reinforced thermoplastic composites. Thermoplastic fiber reinforced laminates have been widely used in aerospace, automobile industry, wind power generation, sports and leisure equipment and other fields because of their light weight, high specific modulus, high specific strength, corrosion resistance and other excellent properties.

The traditional forming process of CFRTP needs to heat the CFRTP above the melting end temperature of the high molecular polymer. At this temperature, the CFRTP is in a completely melted state, so it has better fluidity. In this case, when CFRTP is formed, the forming pressure will force the reinforcing fibers to change the arrangement direction under the flow of resin, which seriously weakens the reinforcing effect of fibers in the resin and greatly affects the mechanical properties of CFRTP after forming.

Contents of the invention

The object of the present invention is to provide a forming and processing method of crystalline CFRTP to overcome the problem that the fiber reinforcement effect of the resin is weakened during the forming process of CFRTP.

In order to realize the above-mentioned purpose of the present invention, special adopt following technical scheme:

A forming and processing method of crystalline CFRTP, comprising:

After the CFRTP is heated until the CFRTP is completely melted, the CFRTP is put into a cooling medium for quenching treatment;

After the cooled CFRTP is heated until the CFRTP is in a rubber state, the forming process of the CFRTP is started, and at the same time, the heating of the CFRTP is continued, and the forming process of the CFRTP is completed before the CFRTP is completely melted and heating the CFRTP after the forming treatment to a completely molten state, and then cooling it naturally.

Further, in a preferred embodiment of the present invention, during the process of heating the cooled CFRTP, the heating rate is 10-20° C./min.

Further, in a preferred embodiment of the present invention, in the process of heating the cooled CFRTP, when the temperature reaches the melting start temperature of the CFRTP, continue to heat at a rate of 10-20°C/min The CFRTP is heated and at the same time the forming process of the CFRTP is started.

Further, in a preferred embodiment of the present invention, the time for forming the CFRTP is 30-45s.

Further, in a preferred embodiment of the present invention, the final temperature of the heat treatment for the cooled CFRTP is 15-25° C. above the melting end temperature.

Further, in a preferred embodiment of the present invention, after heating the CFRTP to 15-25° C. above the melting end temperature, keep it warm for 10-15 minutes, and then cool naturally.

Further, in a preferred embodiment of the present invention, during the quenching process, the final temperature for heating the CFRTP is 15-25° C. above the melting end temperature.

Compared with prior art, the beneficial effect of the present invention is:

The forming and processing method of this CFRTP provided by the present invention changes the crystallinity and the size of spherulites inside the resin through the quenching treatment of first heating up and then rapidly cooling down. Sufficient crystallization increases the number of incompletely crystalline crystals in the resin, so that when CFRTP is reheated, it will appear like an amorphous polymer rubber state. At the same time, compared with the original CFRTP, the melting start temperature of the quenched CFRTP is lowered by 10-15°C, and the melting end temperature remains basically unchanged, that is, the melting range of the quenched CFRTP is increased by 10-15°C. Forming in the rubbery state provides deformation time.

Since the incompletely crystallized crystal melts first at a lower temperature, the phenomenon that the incompletely crystallized crystal melts first and the completely crystallized crystal melts, when CFRTP is in a rubber state (that is, heating CFRTP above the melting start temperature and melting end temperature The following times) perform forming treatment on CFRTP, so that the entire forming process is in the stage where some segments of the polymer move, but the entire polymer chain does not move, thus effectively solving the problem of weakening fiber reinforcement caused by resin flow. In addition, the resin is in a rubber state during the forming process, and has certain deformation ability and mechanical properties; the temperature rises at the same time during the deformation process, so that the resin continuously changes from solid to liquid, which can effectively solve the internal stress problem caused by CFRTP deformation.

Therefore, compared with the traditional forming process, the forming temperature of the present invention is below the complete melting temperature of the resin, which effectively avoids the problem of fiber bundle flow caused by resin flow, improves the mechanical properties of CFRTP after forming, and the forming process of the present invention can realize The separation of CFRTP preparation and shaping facilitates the implementation of standardization.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art.

Fig. 1 is the DSC curve of the carbon fiber/polyamide 6 composite plate after quenching in Example 1.

Detailed ways

Embodiments of the present invention will be described in detail below in conjunction with examples, but those skilled in the art will understand that the following examples are only for illustrating the present invention, and should not be considered as limiting the scope of the present invention. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased from the market.

This embodiment provides a forming and processing method of crystalline CFRTP, which includes:

Step S1, quenching treatment: heating the prefabricated CFRTP plate until the CFRTP is completely melted, then putting the CFRTP into a cooling medium for quenching treatment.

Put the CFRTP in the molten state into the cooling medium for rapid cooling to reduce the chance of rearrangement and recrystallization of polymer chains, increase the number of incomplete crystals with more defects, and change the crystallinity and spherulites inside the resin. size, and widen the melting range of CFRTP, which is beneficial to buy more time for the subsequent deformation process.

The reason why the quenching treatment can widen the melting range of the resin is that the melting limit range of the polymer crystal is related to the degree of perfection of the crystal structure. When the polymer is rapidly cooled from the molten state, it will cause the polymer chains to fail to form relatively perfect crystals when they are regularly arranged into crystals, and the crystallization stays at different stages, that is, there will be many kinds of crystals with different degrees of perfection in the polymer crystals at the same time. crystalline structure. Subsequently, under the condition of increasing temperature, the polymer crystals with a poor degree of perfection melt first at a lower temperature, while the polymer crystals with a higher degree of perfection melt at a higher temperature, so there is a phenomenon of melting while heating up. The phenomenon widens the melting range of the resin.

Further, the final temperature of heating CFRTP is 15-25° C. above the melting end temperature, and the temperature is kept at this temperature for 10-15 minutes. When CFRTP is heated to 15-25°C above the melting end temperature of the resin and kept for 10-15 minutes, CFRTP is in a completely melted state, which can completely destroy the crystallization between polymer molecular chains, and suppress the high temperature for subsequent rapid cooling. Molecular polymer crystallization preparation.

Further, the cooling medium is water at normal temperature or steel plate at normal temperature.

Step S2, heating and deformation treatment: heating the cooled CFRTP plate until the CFRTP is in a rubbery state, then start forming the CFRTP, and continue to heat the CFRTP, and complete the CFRTP before the CFRTP is in a completely melted state Forming treatment.

When CFRTP is in a rubbery state, the resin has certain deformation ability and mechanical properties. This characteristic is used to ensure that the resin will not flow in a large area during the forming process to affect the direction of the reinforcing fibers, thereby effectively solving the problem of resin flow in the traditional CFRTP forming process. During the deformation process, the temperature increases at the same time, and the high molecular polymer is continuously converted from solid to liquid, which can coordinate the internal stress caused by deformation.

Since the quenched CFRTP contains more defective crystals, the thermal movement of polymer molecular chains increases during the heating process, and the imperfect polymer crystals can be destroyed at lower temperatures, that is, the incomplete crystals melt first. , melted after fully crystallized crystals. Therefore, the entire forming process is in the stage where some segments of the resin polymer move but the whole does not move, thereby avoiding resin flow during the forming process.

Further, during the process of heating the cooled CFRTP, the heating rate is 10-20° C./min.

Further, in the process of heating the cooled CFRTP, when the temperature reaches the melting start temperature of CFRTP, continue to heat CFRTP at a heating rate of 10-20°C/min, and at the same time perform shaping treatment on CFRTP.

Further, the time for forming the CFRTP is 30-45s.

After CFRTP is quenched, the melting process is broadened, which provides forming time for forming. The inventor found that when the quenched CFRTP is heated at a heating rate of 10-20°C/min, and then DSC test is performed, it is found that the melting range of CFRTP can be increased by 10-15°C when the temperature rises at 10°C/min ℃. Therefore, when forming at a heating rate of 10-20°C/min, the forming time should be kept within 30-45s.

Step S3, cooling: heating the formed CFRTP to a completely melted state, and then naturally cooling to normal temperature.

Further, the final temperature of the heat treatment for the cooled CFRTP is 15-25° C. above the melting end temperature.

Further, after heating the CFRTP to 15-25°C above the melting end temperature, keep it warm for 10-15 minutes, and then cool it down naturally. Preferably, the final temperature is 20°C above the melting end temperature of CFRTP, and the temperature is kept for 15 minutes. This step can completely melt the resin, and then air-cool to room temperature, reduce excessive cooling, restore CFRTP crystallinity, and restore the mechanical properties of CFRTP.

It should be noted that, in this application, "melting start temperature" refers to the starting temperature of the melting peak in the DSC curve; "melting end temperature" refers to the ending temperature of the melting peak in the DSC curve. "Melting" means that the resin is in a state where solid and liquid coexist; "melting" means that the resin is in a completely liquid state.

Below in conjunction with embodiment, feature and performance of the present invention are described in further detail:

Example 1

This embodiment provides a forming and processing method for crystalline CFRTP. Since polyamide 6 is a crystalline polymer commonly used as a resin matrix for thermoplastic fiber-reinforced composite materials, this embodiment uses carbon fiber/polyamide 6 composite The board is the raw material for processing, and its DSC curve is shown in Figure 1, which specifically includes the following steps:

Step (1) First, quench the carbon fiber/polyamide 6 composite board: heat the prepared carbon fiber/polyamide 6 composite board to 250°C and keep it warm for 15 minutes until the resin is completely melted, then quickly heat the carbon fiber/polyamide 6 composite board Put it between two normal temperature steel plates for rapid cooling. Through the rapid cooling of polyamide 6, the crystallization of polyamide 6 crystals is in different stages, thereby widening the melting range.

Step (2) Heating and deformation: After step (1), heat the carbon fiber/polyamide 6 composite board at a heating rate of 10°C/min. When the temperature reaches 200°C, put the carbon fiber/polyamide 6 composite board into the Stamping begins in the mold. The mold temperature was 220°C. When the upper mold and the lower mold are fully attached, the mold starts to heat up to 250°C and keep warm for 15 minutes to completely melt the carbon fiber/polyamide 6. The heating and forming treatment are carried out at the same time, and the time for forming the carbon fiber/polyamide 6 composite plate is controlled within 30-45s. The forming process ends before the polyamide 6 is completely melted, and the mechanical properties of the unmelted polyamide 6 are used to constrain the arrangement direction of the fibers, so as to prevent the resin flow from affecting the arrangement direction of the fibers.

Step (3) cooling; mold opening, air cooling to normal temperature. Restore the crystallinity of polyamide 6 and restore the mechanical properties of polyamide 6.

Example 2

This embodiment provides a forming and processing method for crystalline CFRTP. Since polyamide 6 is a crystalline polymer commonly used as a resin matrix for thermoplastic fiber-reinforced composite materials, this embodiment uses carbon fiber/polyamide 6 composite The board is the raw material for processing, and the specific implementation includes the following steps:

Step (1) First, quench the carbon fiber/polyamide 6 composite board: heat the prepared carbon fiber/polyamide 6 composite board to 245°C and keep it warm for 20 minutes until the resin is completely melted, then quickly heat the carbon fiber/polyamide 6 composite board Quickly cool in coolant.

Step (2) Heating and deformation: After step (1), put the carbon fiber/polyamide 6 composite board and the mold into a vacuum bag, and seal the vacuum bag. Heat the vacuum bag as a whole at a heating rate of 5°C/min. When the temperature reaches 200°C, start to evacuate the vacuum bag and heat the vacuum bag as a whole at a heating rate of 5°C/min. The heating and forming treatment are carried out at the same time, the deformation time of the carbon fiber/polyamide 6 composite plate should be controlled within 30-45s, and the forming step should be completed before the heating temperature reaches 220°C. Finally, heat it to 245°C and keep it warm for 15 minutes, so that the carbon fiber/polyamide 6 is in a completely melted state.

Step (3) cooling; air cooling to normal temperature. Take out the finished carbon fiber/polyamide 6 composite board.

Example 3

This embodiment provides a forming and processing method for crystalline CFRTP. Since polyamide 6 is a crystalline polymer commonly used as a resin matrix for thermoplastic fiber-reinforced composite materials, this embodiment uses carbon fiber/polyamide 6 composite The board is the raw material for processing, and the specific implementation includes the following steps:

Step (1) First, quench the carbon fiber/polyamide 6 composite board: heat the prepared carbon fiber/polyamide 6 composite board to 250°C and keep it warm for 10 minutes until the resin is completely melted, then quickly heat the carbon fiber/polyamide 6 composite board Quickly cool in coolant.

Step (2) Heating and deformation: After step (1), put the carbon fiber/polyamide 6 composite board and the mold into a vacuum bag, and seal the vacuum bag. Heat the vacuum bag as a whole at a heating rate of 5°C/min. When the temperature reaches 200°C, start to evacuate the vacuum bag and heat the vacuum bag as a whole at a heating rate of 5°C/min. The heating and forming treatment are carried out at the same time, the deformation time of the carbon fiber/polyamide 6 composite plate should be controlled within 30-45s, and the forming step should be completed before the heating temperature reaches 220°C. Finally, heat it to 250°C and keep it warm for 15 minutes, so that the carbon fiber/polyamide 6 is completely melted.

Step (3) cooling; air cooling to normal temperature. Take out the finished carbon fiber/polyamide 6 composite board.

It should be noted at last that each embodiment described above is only used to illustrate the technical solution of the present invention, and is not intended to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (7)

1. A forming method of crystalline CFRTP, characterized in that it comprises: After the CFRTP is heated until the CFRTP is completely melted, the CFRTP is put into a cooling medium for quenching treatment; After the cooled CFRTP is heated until the CFRTP is in a rubbery state, the forming process of the CFRTP is started, and at the same time, the heating of the CFRTP is continued, and the forming process of the CFRTP is completed before the CFRTP is completely melted and heating the CFRTP after the forming treatment to a completely molten state, and then cooling it naturally. 2 . The forming method of crystalline CFRTP according to claim 1 , characterized in that, in the process of heating the cooled CFRTP, the heating rate is 10-20° C./min. 3. The forming processing method of crystalline CFRTP according to claim 2, characterized in that, in the process of heating the cooled CFRTP, after the temperature reaches the melting start temperature of the CFRTP, continue to use 10 The CFRTP is heated at a heating rate of -20° C./min, and at the same time, the forming process of the CFRTP is started. 4. The method for forming and processing crystalline CFRTP according to claim 1, characterized in that, the time for forming the CFRTP is 30-45s. 5 . The molding method of crystalline CFRTP according to claim 1 , wherein the final temperature of the heat treatment for the cooled CFRTP is 15-25° C. above the melting end temperature. 6 . 6 . The forming and processing method of crystalline CFRTP according to claim 5 , characterized in that, after heating the CFRTP to 15-25° C. above the melting end temperature, keep it warm for 10-15 minutes, and then cool it down naturally. 6 . 7. The forming method of crystalline CFRTP according to claim 1, characterized in that, during the quenching process, the final temperature of heating the CFRTP is 15-25° C. above the melting end temperature.