阅读说明：本技术 内嵌热塑性膜的复合材料层合板抗冲击设计及其制备方法 (Impact-resistant design and preparation method of composite laminated plate with embedded thermoplastic film ) 是由 赵天 王冠华 李营 于 2021-01-25 设计创作，主要内容包括：本发明涉及一种内嵌热塑性膜的复合材料层合板的抗冲击设计及其制备方法,属于复合材料技术领域。内嵌热塑性膜的复合材料层合板,从构型优化角度对复合材料层合板结构进行改性设计,所提出的复合材料层合板结构是在普通(热固性)环氧树脂基复合材料层合结构中放置热塑性聚合物薄膜,在不显著增加结构重量的前提下,提升结构整体的抗冲击性能。本发明在不显著增加结构重量的前提下,较大幅度提升结构整体的抗冲击性能,包括面外刚度、抵抗变形能力,以及抵抗分层能力等。有效提升了传统热固性环氧树脂基复合材料层合板结构的抗冲击性能与在动态载荷下的损伤容限。(The invention relates to an impact-resistant design of a composite material laminated plate embedded with a thermoplastic film and a preparation method thereof, belonging to the technical field of composite materials. The composite material laminated plate with the embedded thermoplastic film is characterized in that the structure of the composite material laminated plate is modified and designed from the configuration optimization angle, and the provided composite material laminated plate structure is formed by placing a thermoplastic polymer film in a common (thermosetting) epoxy resin-based composite material laminated structure, so that the integral impact resistance of the structure is improved on the premise of not remarkably increasing the weight of the structure. On the premise of not increasing the weight of the structure obviously, the invention greatly improves the integral shock resistance of the structure, including out-of-plane rigidity, deformation resistance, delamination resistance and the like. The impact resistance and damage tolerance under dynamic load of the traditional thermosetting epoxy resin-based composite material laminated plate structure are effectively improved.)

1. A thermoplastic film embedded composite laminate characterized by: the thermoplastic polymer film is placed in the common thermosetting epoxy resin-based composite material laminated structure, and the overall impact resistance of the structure is improved on the premise of not obviously increasing the weight of the structure.

2. The thermoplastic film embedded composite laminate of claim 1, wherein: the thermoplastic polymer film and the epoxy resin-based composite material laminated structure are alternately arranged; or the thermoplastic polymer films and the multilayer epoxy resin-based composite material laminated structure are alternately arranged.

3. The thermoplastic film embedded composite laminate of claim 1 or 2, wherein: the thermoplastic polymer film is placed inside, on top of, on the bottom of, or both the top and bottom of a monolithic structure, i.e., a composite laminate with embedded thermoplastic film.

4. The thermoplastic film embedded composite laminate of claim 1 or 2, wherein: the epoxy resin-based composite material laminating structure is prepared from a plurality of layers of carbon fiber prepregs; the carbon fiber prepreg layer consists of two carbon fiber prepregs in the same direction; the thickness of the thermoplastic polymer film is similar to that of a single carbon fiber prepreg.

5. The thermoplastic film embedded composite laminate of claim 4, wherein: the thickness of the thermoplastic polymer film was 0.15 mm.

6. The thermoplastic film embedded composite laminate of claim 4, wherein: the curing temperature of the carbon fiber prepreg is 180 +/-5 ℃, and is close to the glass transition temperature of the adopted thermoplastic polymer.

7. The thermoplastic film embedded composite laminate of claim 1 or 2, wherein: the first structure of the composite material laminated plate embedded with the thermoplastic film is as follows: the composite material consists of eight layers of fiber layers and three layers of thermoplastic film layers, wherein each layer of the carbon fiber layer consists of two carbon fiber prepregs in the same direction, and each layer of the thermoplastic film layer consists of one thermoplastic film; the stacking direction, from bottom to top, is given by: the first, third, sixth and eighth layers are fiber layers in the direction of 0 degree, and the second, fourth, fifth and seventh layers are fiber layers in the direction of 90 degree; the three thermoplastic material layers are respectively arranged between two, three, four, five and six seven carbon fiber layers.

The structure II of the composite material laminated plate embedded with the thermoplastic film is as follows: the composite material consists of eight layers of fiber layers and three layers of thermoplastic film layers, wherein each layer of the carbon fiber layer consists of two carbon fiber prepregs in the same direction, and each layer of the thermoplastic film layer consists of one thermoplastic film; the stacking direction, from bottom to top, is given by: the first, third, sixth and eighth layers are fiber layers in the direction of 0 degree, and the second, fourth, fifth and seventh layers are fiber layers in the direction of 90 degree; the three thermoplastic material layers are respectively arranged between the fourth five carbon fiber layer and the sixth seven carbon fiber layer and on the eighth carbon fiber layer.

The structure III of the composite material laminated plate embedded with the thermoplastic film is as follows: the composite material consists of eight layers of fiber layers and three layers of thermoplastic film layers, wherein each layer of the carbon fiber layer consists of two carbon fiber prepregs in the same direction, and each layer of the thermoplastic film layer consists of one thermoplastic film; the stacking direction, from bottom to top, is given by: the first, third, sixth and eighth layers are fiber layers in the direction of 0 degree, and the second, fourth, fifth and seventh layers are fiber layers in the direction of 90 degree; three thermoplastic material layers are respectively arranged below one carbon fiber layer and between the second three-five carbon fiber layer and the fourth five-five carbon fiber layer.

The composite material laminated plate embedded with the thermoplastic film has the following structure: the composite material consists of eight layers of fiber layers and three layers of thermoplastic film layers, wherein each layer of the carbon fiber layer consists of two carbon fiber prepregs in the same direction, and each layer of the thermoplastic film layer consists of one thermoplastic film; the stacking direction, from bottom to top, is given by: the first, third, sixth and eighth layers are fiber layers in the direction of 0 degree, and the second, fourth, fifth and seventh layers are fiber layers in the direction of 90 degree; the three thermoplastic material layers are respectively arranged below the first fiber layer, between the four five carbon fiber layers and above the eight carbon fiber layers.

8. A method of making a thermoplastic film embedded composite laminate according to claim 1 or 2, wherein: the method comprises the following steps:

step one, placing the carbon fiber prepreg at 25 +/-2 ℃ for more than 10 hours for softening adjustment, and cleaning a mold;

secondly, laying carbon fiber prepreg on the lower die surface according to the designed laying structure;

covering an upper die, sealing the die, and vacuumizing the die;

and step four, completing high-temperature forming according to the designed forming process, opening the mould, and taking out the composite material to obtain the composite material laminated plate embedded with the thermoplastic film based on the fiber prepreg.

9. The method of claim 8, wherein:

in the third step, the molding materials adopted by the vacuumized laying of the laminated board mould comprise sealing rubber strips, isolating films, fiber fabrics, air-permeable felts, vacuum bags and metal strips;

in the third step, the operation of sealing the mold includes: fixing the prepreg paving plate on a mould by using three rubber adhesive tapes with the same thickness as the prepreg paving plate and one metal strip with the same specification, paving an isolation film, a fiber fabric and an air felt on the mould in sequence, pasting a sealing adhesive tape along the edge of the mould, paving a vacuum bag on the air felt, and tightly pasting the vacuum bag on the sealing adhesive tape;

and in the fourth step, curing the composite laminated plate in the autoclave curing process according to a curing system, wherein the curing system is as follows:

1) vacuumizing, wherein the pressure in a vacuum bag is not less than 0.08MPa, and the pressure applied in an autoclave is 0.6-0.8 MPa;

2) maintaining the pressure, and heating from room temperature to 180 +/-5 ℃ at a heating rate of 0.5-3 ℃/min;

3) keeping the temperature at 180 + -5 deg.C under 0.6-0.8 MPa for at least 180 min;

4) cooling to below 60 ℃ at a cooling rate of not more than 3 ℃/min.

Technical Field

The invention relates to an impact-resistant design of a composite laminated plate embedded with a thermoplastic film and a preparation method thereof, belonging to the technical field of composite materials.

Background

The carbon fiber composite material (CFRP) is mainly used in the advanced scientific and technical fields of military industry, aerospace, aviation and the like since the 20 th century and the 50 th era, and has unique properties of high strength, high modulus, light weight, heat resistance, corrosion resistance and the like, so that the CFRP plays a great role in the aspects of airplanes, rockets, missiles, artificial satellites and the like. With the continuous improvement and improvement of the performance of CFRP materials, the excellent performance of the CFRP materials is gradually accepted and the price is greatly reduced, so that the application of the CFRP materials in the civil industry is gradually enlarged, and the CFRP materials are widely applied to the fields of civil construction, textile, petroleum industry, medical machinery, automobile industry and the like.

The specific strength and the specific modulus of the carbon fiber reinforced epoxy resin composite material are the highest in the existing engineering materials. However, the defects of low damage tolerance, poor impact resistance and the like of the traditional carbon fiber reinforced composite material are one of the important problems which puzzle the design field for a long time. Although CFRP has the advantages of light weight, high strength, high modulus, etc., its brittle nature and easy delamination of the structure greatly limit its application expansion. For example, when the CFRP structure is subjected to low-speed impact load (such as tool drop, heavy collision, etc.), although the CFRP structure is good in appearance, the internal structure of the CFRP structure is likely to have some damage which is not easy to detect, such as matrix damage and interlayer delamination, and the damage greatly affects the service performance of the CFRP structure. Therefore, in many structures or components that may be subjected to shock loading, CFRP is often not possible from a safety standpoint, and a more plastic metallic material is forced. The design limitation not only greatly influences the structure lightweight level, but also brings new problems in the aspect of connection of metal and composite materials and the like. Therefore, there is a need to provide a new composite material configuration that can effectively improve the impact resistance and damage tolerance of conventional CFRP structures.

High performance thermoplastic polymer materials have received much attention in the industry in recent years due to their advantages such as good toughness, large damage tolerance, good dielectric constant, and easy and simple processing and molding. However, thermoplastic resin generally has the characteristics of high processing temperature, high viscosity and poor fluidity at high temperature, so that the thermoplastic resin is difficult to effectively compound with fibers, and has high processing difficulty and high cost. Therefore, the combination of the traditional CFRP and the high-performance thermoplastic polymer fully exerts the advantages of the traditional CFRP and the high-performance thermoplastic polymer, improves the overall toughness and the impact resistance of the CFRP structure, and is an effective method. At present, many researches on modifying the traditional CFRP by using thermoplastic resin based on material angles exist, but the researches can only be carried out on the scale of laboratory test pieces and cannot be applied to large-scale equipment structures. Compared with the research, the invention provides the composite material laminated plate embedded with the thermoplastic film and the preparation method thereof from the structural design angle, does not need to fundamentally change the preparation process, can carry out industrial-grade rapid production based on the existing composite material manufacturing process, and has important application prospect.

Disclosure of Invention

The invention aims to solve the problems of insufficient impact resistance and damage tolerance of the conventional CFRP structure, and provides a composite material laminated plate embedded with a thermoplastic film and a preparation method thereof.

The purpose of the invention is realized by the following technical scheme.

The composite material laminated plate with the embedded thermoplastic film is characterized in that the structure of the composite material laminated plate is modified and designed from the configuration optimization angle, and the provided composite material laminated plate structure is formed by placing a thermoplastic polymer film in a common (thermosetting) epoxy resin-based composite material laminated structure, so that the integral impact resistance of the structure is improved on the premise of not remarkably increasing the weight of the structure.

The thermoplastic polymer film and the epoxy resin-based composite material laminated structure are alternately arranged; the thermoplastic polymer film and the multilayer epoxy resin matrix composite material laminated structure are alternately arranged;

the thermoplastic polymer film is placed inside, on top of, on the bottom of, or both the top and bottom of a monolithic structure, i.e., a composite laminate with embedded thermoplastic film;

the epoxy resin-based composite material laminating structure is prepared from a plurality of layers of carbon fiber prepregs; the carbon fiber prepreg layer consists of two carbon fiber prepregs in the same direction; the thickness of the thermoplastic polymer film is similar to that of a single carbon fiber prepreg;

the thickness is 0.15 mm.

The curing temperature of the carbon fiber prepreg is 180 +/-5 ℃, and is close to the glass transition temperature of the adopted thermoplastic polymer.

The first structure of the composite material laminated plate embedded with the thermoplastic film is as follows: the composite material consists of eight layers of fiber layers and three layers of thermoplastic film layers, wherein each layer of the carbon fiber layer consists of two carbon fiber prepregs in the same direction, and each layer of the thermoplastic film layer consists of one thermoplastic film. The stacking direction, from bottom to top, is given by: the first, third, sixth and eighth layers are fiber layers in the direction of 0 degree, and the second, fourth, fifth and seventh layers are fiber layers in the direction of 90 degree. The three thermoplastic material layers are respectively arranged between two, three, four, five and six seven carbon fiber layers.

The structure II of the composite material laminated plate embedded with the thermoplastic film is as follows: the composite material consists of eight layers of fiber layers and three layers of thermoplastic film layers, wherein each layer of the carbon fiber layer consists of two carbon fiber prepregs in the same direction, and each layer of the thermoplastic film layer consists of one thermoplastic film. The stacking direction, from bottom to top, is given by: the first, third, sixth and eighth layers are fiber layers in the direction of 0 degree, and the second, fourth, fifth and seventh layers are fiber layers in the direction of 90 degree. The three thermoplastic material layers are respectively arranged between the fourth five carbon fiber layer and the sixth seven carbon fiber layer and on the eighth carbon fiber layer.

The structure III of the composite material laminated plate embedded with the thermoplastic film is as follows: the composite material consists of eight layers of fiber layers and three layers of thermoplastic film layers, wherein each layer of the carbon fiber layer consists of two carbon fiber prepregs in the same direction, and each layer of the thermoplastic film layer consists of one thermoplastic film. The stacking direction, from bottom to top, is given by: the first, third, sixth and eighth layers are fiber layers in the direction of 0 degree, and the second, fourth, fifth and seventh layers are fiber layers in the direction of 90 degree. Three thermoplastic material layers are respectively arranged below one carbon fiber layer and between the second three-five carbon fiber layer and the fourth five-five carbon fiber layer.

The composite material laminated plate embedded with the thermoplastic film has the following structure: the composite material consists of eight layers of fiber layers and three layers of thermoplastic film layers, wherein each layer of the carbon fiber layer consists of two carbon fiber prepregs in the same direction, and each layer of the thermoplastic film layer consists of one thermoplastic film. The stacking direction, from bottom to top, is given by: the first, third, sixth and eighth layers are fiber layers in the direction of 0 degree, and the second, fourth, fifth and seventh layers are fiber layers in the direction of 90 degree. The three thermoplastic material layers are respectively arranged below the first fiber layer, between the four five carbon fiber layers and above the eight carbon fiber layers.

A method of making the thermoplastic film embedded composite laminate comprising the steps of:

step one, placing the carbon fiber prepreg at 25 +/-2 ℃ for more than 10 hours for softening adjustment, and cleaning a mold;

secondly, laying carbon fiber prepreg on the lower die surface according to the designed laying structure;

covering an upper die, sealing the die, and vacuumizing the die;

and step four, completing high-temperature forming according to the designed forming process, opening the mould, and taking out the composite material to obtain the composite material laminated plate embedded with the thermoplastic film based on the fiber prepreg.

Furthermore, in the third step, the molding material adopted for the vacuum-pumping laying of the laminate mold comprises a sealing rubber strip, an isolating film, a fiber fabric, an air-permeable felt, a vacuum bag and a metal strip.

Further, in the third step, the operation of sealing the mold includes: fixing the prepreg paving plate by three rubber adhesive tapes with the same thickness as the prepreg paving plate and one metal strip with the same specification, paving an isolation film, a fiber fabric and an air felt on a mould in sequence, pasting a sealing adhesive tape along the edge of the mould, paving a vacuum bag on the air felt and tightly pasting the vacuum bag on the sealing adhesive tape.

Furthermore, in the fourth step, the composite material laminate should be cured strictly according to a curing system in the autoclave curing process, wherein the curing system is as follows:

1) vacuumizing, wherein the pressure in the vacuum bag is not less than 0.08MPa, and the pressure applied in the autoclave is 0.6-0.8 MPa.

2) Maintaining the pressure, and heating from room temperature to 180 +/-5 ℃ at a heating rate of 0.5-3 ℃/min.

3) Keeping the temperature at 180 + -5 deg.C under 0.6-0.8 MPa for at least 180 min.

4) Cooling to below 60 deg.C at a cooling rate of not more than 3 deg.C/min (maintaining autoclave pressure until cooling is complete).

Advantageous effects

1. According to the invention, through structural design optimization, the composite material laminated plate structure with the embedded thermoplastic film is provided, and on the premise of not remarkably increasing the structure weight, the overall impact resistance of the structure, including out-of-plane rigidity, ultimate bearing capacity, delamination resistance and the like, is greatly improved, compared with the traditional CFRP, the weight is increased by only 20%, the ultimate bearing capacity can be improved by 50%, and the delamination area after impact is reduced by 46.7%. The invention effectively improves the shock resistance and the damage tolerance under dynamic load of the traditional thermosetting epoxy resin-based composite material laminated plate structure;

2. according to the invention, through introducing the thermoplastic film, the internal thermoplastic film is elastically deformed when being impacted, so that the impact effect is reduced at the first time, and due to the introduction of the thermoplastic film, the bonding capability of an interlayer interface is increased and the anti-layering capability of the carbon fiber composite laminated plate under complex acting force is improved due to the good bonding property of the thermoplastic film and the epoxy resin base.

3. The preparation method of the composite material laminated plate embedded with the thermoplastic film is simple to operate, and industrial production can be completed by adopting the existing process.

Drawings

FIG. 1 shows four structures of a carbon fiber composite material laminate with an embedded thermoplastic film; wherein FIG (a) is a structural view of embodiment 1; FIG. (b) is a structural view of example 2; FIG. (c) is a structural view of embodiment 3; FIG. (d) is a structural view of embodiment 4;

FIG. 2 is a film-prepreg transition interface in a carbon fiber composite laminate with embedded thermoplastic film;

FIG. 3 is a scan of C after impact for CFRP and various examples and comparative examples: the diagram a is a layering diagram (layering area in a wire frame) after impact, and the diagram b is a layering area bar diagram;

FIG. 4 is a bar graph of peak force at impact for each example and comparative example;

FIG. 5 is an impact force versus time plot for a control test piece of a CFRP laminate without a thermoplastic film;

FIG. 6 is a graph of impact force versus time for four examples: FIG. a is a graph of impact force vs. time for example 1; FIG. b is a graph of impact force versus time for example 2; FIG. c is a graph of impact force versus time for example 3; FIG. d is a graph of impact force versus time for example 4;

FIG. 7 is a comparative graph of SEM observed damage after impact for comparative test pieces of example 2 and comparative CFRP;

Detailed Description

In order to more clearly illustrate the technical solutions of the present invention, the following description is given with reference to specific embodiments and accompanying drawings, and it is obvious that the embodiments in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other embodiments can be obtained according to these embodiments without any inventive work.

The thermoplastic material is introduced into the composite material laminated plate embedded with the thermoplastic film, so that the structural integrity of the composite material laminated plate needs to be verified after a test sample is prepared, so that the preparation method is true and effective. It can be seen from fig. 2 that the carbon fiber prepreg layer and the thermoplastic film layer do not show distinct zones, but instead the two materials are mutually fused during co-curing, the boundary of the two materials being shown in the form of interphase, and it can be seen that a part of the resin globules in the resin zone flows into the thermoplastic film in the form of a reinforcing factor, and this form of interphase enables a better bonding of the carbon fiber prepreg layer and the thermoplastic film layer.

In order to verify the improvement of the impact resistance of the composite material laminate with the embedded thermoplastic film, drop hammer impact tests were respectively carried out for different prepared structural configurations, and a CFRP laminate structure without the thermoplastic film was used as a reference.

Example 1

The configuration laminate prepared in this example was a carbon fiber prepreg, which is an epoxy resin prepreg of carbon fiber. The specific content comprises the following steps:

step one, taking out qualified carbon fiber prepreg from a refrigerator according to experimental requirements, placing the carbon fiber prepreg at the room temperature of 25 +/-2 ℃ for more than 10 hours for softening adjustment, and cleaning a mold;

secondly, cleaning the surface of the mould, and wiping the outer surfaces of the upper mould and the lower mould with alcohol; according to the design structure, the first structural layer is composed of eight fiber layers and three PEI (polyetherimide) thermoplastic film layers, each carbon fiber layer is composed of two carbon fiber prepregs in the same direction, and each thermoplastic film layer is composed of one thermoplastic film. The first, third, sixth and eighth layers are fiber layers in the direction of 0 degree, and the second, fourth, fifth and seventh layers are fiber layers in the direction of 90 degree. The three thermoplastic material layers are respectively arranged between two, three, four, five and six seven carbon fiber layers. When a PEI thermoplastic material film is laid, IPA (isopropyl alcohol) is used for cleaning the surface of the thermoplastic material film and the surface of the carbon fiber layer in order to ensure that the prepreg layer and the PEI thermoplastic material film are better fused in the co-curing process;

thirdly, removing the prepreg release paper on the outermost layer, and covering an upper die; paving a glue absorption felt on the surface of an upper die, and sticking a sealing adhesive tape along the edge of the die; laying the prepared vacuum bag film on a glue absorption felt, gradually removing the isolation paper of the sealing rubber strip, tightly attaching the vacuum bag film on the sealing rubber strip, and connecting a vacuum suction nozzle;

and fourthly, completing high-temperature forming according to the designed forming process, opening the mould, and taking out the composite material to obtain the carbon fiber laminated plate with the composite material laminated plate embedded with the thermoplastic film.

The resulting composite laminate was subjected to drop weight test according to ASTM D7136/D7136-7 with an energy setting of 15J using a hemispherical hammer head with a diameter of 8mm to give a laminate with an ultimate bearing capacity of 3.2kN and an absorbed energy of 12.16J.

Example 2

In this example, a two-layer laminate of a composite laminate embedded with a thermoplastic film was prepared, in which the carbon fiber prepreg was an epoxy resin prepreg of carbon fiber. The specific content comprises the following steps:

step one, taking out qualified carbon fiber prepreg from a refrigerator according to experimental requirements, placing the carbon fiber prepreg at the room temperature of 25 +/-2 ℃ for more than 10 hours for softening adjustment, and cleaning a mold; according to design requirements, guiding a cutting design drawing into a computer, and cutting the carbon fiber prepreg through a numerical control cutting bed;

secondly, cleaning the surface of the mould, and wiping the outer surfaces of the upper mould and the lower mould with alcohol; according to the design structure, the second configuration layer is composed of eight fiber layers and three PEI (polyetherimide) thermoplastic film layers, each carbon fiber layer is composed of two carbon fiber prepregs in the same direction, and each thermoplastic film layer is composed of one thermoplastic film. The first, third, sixth and eighth layers are fiber layers in the direction of 0 degree, and the second, fourth, fifth and seventh layers are fiber layers in the direction of 90 degree. Three thermoplastic material layers are respectively arranged between the first carbon fiber layer and between the two-three-five carbon fiber layer and the four-five carbon fiber layer. When a PEI thermoplastic material film is laid, IPA (isopropyl alcohol) is used for cleaning the surface of the thermoplastic material film and the surface of the carbon fiber layer in order to ensure that the prepreg layer and the PEI thermoplastic material film are better fused in the co-curing process;

thirdly, removing the prepreg release paper on the outermost layer, and covering an upper die; paving a glue absorption felt on the surface of an upper die, and sticking a sealing adhesive tape along the edge of the die; laying the prepared vacuum bag film on a glue absorption felt, gradually removing the isolation paper of the sealing rubber strip, tightly attaching the vacuum bag film on the sealing rubber strip, and connecting a vacuum suction nozzle;

and fourthly, completing high-temperature forming according to the designed forming process, opening the mould, and taking out the composite material to obtain the carbon fiber laminated plate of the composite material laminated plate with the embedded thermoplastic film.

The resulting composite laminate was subjected to drop weight test according to ASTM D7136/D7136-7 with an energy setting of 15J using a hemispherical hammer head with a diameter of 8mm to give a laminate with an ultimate bearing capacity of 3.8kN and an absorbed energy of 11.35J.

Example 3

In this example, a three-layer laminate sheet of a composite material laminate sheet embedded with a thermoplastic film was prepared, in which the carbon fiber prepreg was an epoxy resin prepreg of carbon fiber. The specific content comprises the following steps:

step one, taking out qualified carbon fiber prepreg from a refrigerator according to experimental requirements, placing the carbon fiber prepreg at the room temperature of 25 +/-2 ℃ for more than 10 hours for softening adjustment, and cleaning a mold; according to design requirements, guiding a cutting design drawing into a computer, and cutting the carbon fiber prepreg through a numerical control cutting bed;

secondly, cleaning the surface of the mould, and wiping the outer surfaces of the upper mould and the lower mould with alcohol; according to the design structure, the third configuration comprises eight fiber layers and three thermoplastic film layers, each carbon fiber layer comprises two carbon fiber prepregs in the same direction, and each thermoplastic film layer comprises one thermoplastic film. The first, third, sixth and eighth layers are fiber layers in the direction of 0 degree, and the second, fourth, fifth and seventh layers are fiber layers in the direction of 90 degree. The three thermoplastic material layers are respectively arranged between the third four carbon fiber layers, the fifth six carbon fiber layers and the eighth carbon fiber layer. When a PEI thermoplastic material film is laid, IPA (isopropyl alcohol) is used for cleaning the surface of the thermoplastic material film and the surface of the carbon fiber layer in order to ensure that the prepreg layer and the PEI thermoplastic material film are better fused in the co-curing process;

thirdly, removing the prepreg release paper on the outermost layer, and covering an upper die; paving a glue absorption felt on the surface of an upper die, and sticking a sealing adhesive tape along the edge of the die; laying the prepared vacuum bag film on a glue absorption felt, gradually removing the isolation paper of the sealing rubber strip, tightly attaching the vacuum bag film on the sealing rubber strip, and connecting a vacuum suction nozzle;

and fourthly, completing high-temperature forming according to the designed forming process, opening the mould, and taking out the composite material to obtain the carbon fiber laminated plate of the three-layer laminated plate with the composite material laminated plate embedded with the thermoplastic film.

The resulting composite laminate was subjected to drop weight test according to ASTM D7136/D7136-7 with an energy setting of 15J using a hemispherical hammer head with a diameter of 8mm to give a laminate with an ultimate bearing capacity of 3.6kN and an absorbed energy of 12.45J.

Example 4

In this example, a four-layer laminate was prepared in a configuration of a composite material laminate with an embedded thermoplastic film, in which the carbon fiber prepreg was an epoxy resin prepreg of carbon fiber. The specific content comprises the following steps:

step one, taking out qualified carbon fiber prepreg from a refrigerator according to experimental requirements, placing the carbon fiber prepreg at the room temperature of 25 +/-2 ℃ for more than 10 hours for softening adjustment, and cleaning a mold; according to design requirements, guiding a cutting design drawing into a computer, and cutting the carbon fiber prepreg through a numerical control cutting bed;

secondly, cleaning the surface of the mould, and wiping the outer surfaces of the upper mould and the lower mould with alcohol; according to the design structure, the configuration IV consists of eight fiber layers and three thermoplastic film layers, each carbon fiber layer consists of two carbon fiber prepregs in the same direction, and each thermoplastic film layer consists of one thermoplastic film. The first, third, sixth and eighth layers are fiber layers in the direction of 0 degree, and the second, fourth, fifth and seventh layers are fiber layers in the direction of 90 degree. The three thermoplastic material layers are respectively arranged above the first layer of fiber layer, between the four five carbon fiber layers and below the eight carbon fiber layers. When a PEI thermoplastic material film is laid, IPA (isopropyl alcohol) is used for cleaning the surface of the thermoplastic material film and the surface of the carbon fiber layer in order to ensure that the prepreg layer and the PEI thermoplastic material film are better fused in the co-curing process;

thirdly, removing the prepreg release paper on the outermost layer, and covering an upper die; paving a glue absorption felt on the surface of an upper die, and sticking a sealing adhesive tape along the edge of the die; laying the prepared vacuum bag film on a glue absorption felt, gradually removing the isolation paper of the sealing rubber strip, tightly attaching the vacuum bag film on the sealing rubber strip, and connecting a vacuum suction nozzle;

and fourthly, completing high-temperature forming according to the designed forming process, opening the mould, and taking out the composite material to obtain the carbon fiber laminated plate of the composite material laminated plate with the embedded thermoplastic film.

The resulting composite laminate was subjected to drop weight test according to ASTM D7136/D7136-7 with an energy setting of 15J using a hemispherical hammer head with a diameter of 8mm to give a laminate with an ultimate bearing capacity of 3.1kN and an absorbed energy of 12.67J.

Comparative example 1

In this example, a control sample CFRP [0/0/90/90]2s was prepared in which the carbon fiber prepreg was an epoxy resin prepreg of carbon fiber. The specific content comprises the following steps:

step one, taking out qualified carbon fiber prepreg from a refrigerator according to experimental requirements, placing the carbon fiber prepreg at the room temperature of 25 +/-2 ℃ for more than 10 hours for softening adjustment, and cleaning a mold; according to design requirements, guiding a cutting design drawing into a computer, and cutting the carbon fiber prepreg through a numerical control cutting bed;

secondly, cleaning the surface of the mould, and wiping the outer surfaces of the upper mould and the lower mould with alcohol; according to the design structure, firstly 8 layers are laid in the directions of 0 degree, 90 degree and 90 degree, then eight layers are laid in the directions of 90 degree, 0 degree and 0 degree, and isolation plastic films and release paper on the surfaces of two sides of the prepreg are removed in each layer;

thirdly, removing the prepreg release paper on the outermost layer, and covering an upper die; paving a glue absorption felt on the surface of an upper die, and sticking a sealing adhesive tape along the edge of the die; laying the prepared vacuum bag film on a glue absorption felt, gradually removing the isolation paper of the sealing rubber strip, tightly attaching the vacuum bag film on the sealing rubber strip, and connecting a vacuum suction nozzle;

and fourthly, finishing high-temperature forming according to a designed forming process, opening a mould, and taking out the composite material to obtain the carbon fiber laminated plate with the structure of [0/0/90/90]2 s.

The resulting composite laminate was subjected to drop weight test according to ASTM D7136/D7136-7 with an energy setting of 15J using a hemispherical hammer head with a diameter of 8mm to give a laminate with an ultimate bearing capacity of 2.5kN and an absorbed energy of 14.2J.

The test result shows that the thermoplastic film can effectively improve the integral impact resistance of the composite material laminated plate structure. Fig. 3 is a graph of delamination (delamination area within wire frame) and histogram of delamination area after impact for each example and comparative example, and the reason why delamination was greater for example three in fig. 3(a) compared to other examples may be due to the fact that the thermoplastic film of PEI on the back side of the impact during impact acts as a protection for the whole, absorbing impact energy through delamination, and protecting the material from penetration by the hammer head. As can be seen in fig. 3(b), the examples show a comparable reduction in delamination area of around 40% for the same energy impact. FIG. 4 is a bar graph of the peak force at impact for each example versus the comparative example, and it can be seen that each example has a higher load capacity at 15J of impact energy compared to the peak stress for CFRP, with the highest load capacity of example 2 being 50% higher than the CFRP. Fig. 5 and 5 are a graph of impact force versus time for the comparative example CFRP and for each example, respectively, showing a significant load drop after peak for all types of specimens at 15J impact energy, indicating composite fracture at the impact zone. It can be seen from fig. 5 that the comparative CFRP has a long plateau after the impact force reaches the peak until the end of the impact, which indicates that damage processes such as fiber breakage, interlayer separation, etc. occur in the comparative CFRP during the plateau. As shown in the figures of fig. 6, the embodiment shows a progressive damage process and still shows a high residual load-bearing capacity in the Z-direction at the end of the impact.

Fig. 7(a) shows that when the CFRP contrast test piece receives impact, overall deformation occurs first, after the maximum elastic deformation is exceeded, interlayer separation occurs at the impact back, meanwhile, the fibers in the impact area of the impact surface are squeezed, and as the deformation increases, the test piece starts from the impact area on the impact surface, fiber breakage occurs, leading to the longitudinal crack to start to propagate, and so on until the whole contrast test piece is penetrated.

In fig. 7(b), in example 2, due to the thermoplastic material film embedded, when an impact is applied, the first thermoplastic material film absorbs a part of the impact energy by plastic deformation, and then starts to deform as a whole, and after the maximum elastic deformation is exceeded, due to the good bonding effect between the thermoplastic material film and the prepreg, no interlayer separation occurs between the two materials, and damage occurs in the fiber layer, specifically, matrix separation and fiber breakage. As the deformation increases, shear damage occurs to the first thermoplastic film layer of the test piece, and fiber fracture occurs in the impact region on the impact surface, and cracks in the longitudinal direction propagate from the upper layer to the intermediate layer. Meanwhile, interlayer separation and fiber fracture in an impact area occur in the lower layer due to the increase of deformation, and cracks in the longitudinal direction are propagated from the lower layer to the middle layer. When the impact is finished, due to the inhibition of the upper layer and the lower layer on the impact, the second configuration test piece is not penetrated, and the damage of the middle layer is small, so that the second configuration test piece still has certain bearing capacity in the Z direction after being impacted, and has higher damage tolerance.

After the thermoplastic film is introduced into the carbon fiber laminated plate, the damage evolution and the final failure mode of the whole structure under the impact load are obviously changed. It can be seen that the impact resistance of the composite material laminated plate structure embedded with the thermoplastic film is greatly improved, as compared with the weight of the comparative example, as can be seen from the weight of the example shown in table 1, the comparative example only increases the weight by 22%, but the impact resistance limit bearing capacity can be improved by 50% at most, and the structural mode represented by the example 2 shows the optimal performance and has higher damage tolerance, and the strategic advantages of low toughness and low damage tolerance of the traditional CFRP are maintained, and meanwhile, the specific stiffness of the product is additionally improved, and the light weight and high strength of the product are maintained.

TABLE 1 comparison of sample masses

The above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.