CN115959857A

CN115959857A - FIT-based carbon fiber composite material and preparation method thereof

Info

Publication number: CN115959857A
Application number: CN202211063681.7A
Authority: CN
Inventors: 孙锲; 张雪松; 刘问远; 高李泊廷; 康乐; 卢君则; 许世龙; 白玉坤
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2022-08-31
Filing date: 2022-08-31
Publication date: 2023-04-14

Abstract

The invention relates to an FIT-based aviation carbon fiber composite material and a preparation method thereof. The preparation method comprises the steps of modifying a carbon fiber composite laminated plate by using an interlayer functionalization technology (FIT), selecting a polypropylene (PP) non-woven fabric and a polyether sulfone (PES) film with good toughness as interlayer materials, uniformly dispersing multi-wall Carbon Nanotubes (CNTs) on the PP non-woven fabric by using a spraying method, preparing a pure PES film and a CNTs-doped PES conductive thermoplastic film by using a solution casting method respectively, inserting the obtained interlayer materials into a carbon fiber/epoxy resin (CF/EP) prepreg, obtaining the composite laminated plate by using a hot die pressing method, and researching the influence of different interlayer materials on the conductivity and interlayer fracture toughness of the (CF/EP) composite material.

Description

FIT-based carbon fiber composite material and preparation method thereof

Technical Field

The invention belongs to the technical field of composite materials, and particularly relates to a FIT-based carbon fiber composite material and a preparation method thereof.

Background

The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

The use of the composite material in the aerospace field can greatly reduce the weight of the airplane, and the existing full composite material airplane mainly made of the advanced composite material mainly takes CFRP and KFRP as main materials, and the weight of the structure is reduced by 40 percent. At present, the traditional carbon fiber composite materials in China are widely applied to canopy covers, front lifting cabins, wall plates, central wings, ailerons, wings, rear fuselages and the like. The traditional carbon fiber composite material improves the toughness of carbon fibers and the like in an in-situ toughening mode. However, the traditional in-situ toughening sacrifices the good fluidity and the laying property of the prepreg of the thermosetting resin to a certain extent, so that the thermosetting resin cannot meet new process requirements.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides an FIT-based aviation carbon fiber composite material and a preparation method thereof. The invention adopts interlayer dislocation toughening technology to replace in-situ toughening, and the interlayer dislocation toughening is to prevent crack propagation by improving the toughness of an interlayer plastic region so as to achieve the aim of toughening.

In order to solve the technical problems, the invention provides the following technical scheme:

the preparation method comprises the steps of modifying a carbon fiber composite laminated plate by using an interlayer functionalization technology (FIT), selecting a polypropylene (PP) non-woven fabric and a polyether sulfone (PES) film with good toughness as interlayer materials, uniformly dispersing multi-wall Carbon Nanotubes (CNTs) on the PP non-woven fabric by using a spraying method, preparing a pure PES film and a CNTs-doped PES conductive thermoplastic film by using a solution casting method respectively, inserting the obtained interlayer materials into a carbon fiber/epoxy resin (CF/EP) prepreg, obtaining the composite laminated plate by using a hot die pressing method, and researching the influence of different interlayer materials on the conductivity and interlayer fracture toughness of the (CF/EP) composite material.

A preparation method of a FIT-based carbon fiber composite material comprises the following steps:

(1) Preparation of interlayer material: mixing CNTs and PES particles in a solvent, and drying to prepare a PES film containing the CNTs; or loading the CNTs on a PP non-woven fabric to prepare a PP non-woven fabric interlayer material loaded with the CNTs;

(2) Laying carbon fiber/epoxy resin prepreg in the same fiber direction in a mold cavity, laying the interlayer material on the carbon fiber/epoxy resin prepreg, and laying the carbon fiber/epoxy resin prepreg in a smooth manner according to the previous laying direction; and closing the mold, heating, curing at a proper temperature and pressure, stopping heating, cooling to room temperature, and demolding to obtain the carbon fiber composite material.

Further, adding CNTs into a solvent to be uniformly dispersed to obtain a dispersion liquid, pouring PES particles into the dispersion liquid to completely dissolve PES, then pouring the PES particles into a glass dish, and drying to obtain a PES film containing CNTs; or, uniformly dispersing the CNTs in a solvent, uniformly spraying the CNTs solution on the PP non-woven fabric, and drying to volatilize the solvent to obtain the CNTs-loaded PP non-woven fabric interlayer material.

Further, the density of the PP non-woven fabric surface is 15g/m ² And the thickness is 40 mu m.

Further, in the step (1), the solvent is DMF or ethanol.

Furthermore, in the CNTs-loaded PP non-woven fabric interlayer material, the loading amount of the CNTs is 1-20mg/m ² Preferably 10mg/m ² 。

Furthermore, the amount of the CNTs in the PES film containing the CNTs is 5-10wt%.

Furthermore, when the PES film loaded with the CNTs is prepared, the drying temperature is 120 ℃, and the drying time is 3h.

Further, when the CNTs-loaded PP non-woven fabric interlayer material is prepared, the drying temperature is 40 ℃ and the drying time is 30min.

Further, the number of carbon fiber/epoxy resin prepregs laid twice is 5 to 20, preferably 12.

Further, in the step (2), the curing conditions are as follows: curing for 30min under the conditions of 0.6MPa and 80 ℃, keeping the pressure unchanged, continuously heating to 130 ℃, and keeping the temperature for 90min.

"interlayer functionalization technology (FIT)" is a toughening technology aimed at improving interlayer impact tolerance, developed from ex-situ toughening (ES). In summary, the FIT technology is a technology that pretreats a thermoplastic network structure having a toughening effect to load a nano-scale conductive material on its fibers and finally transfers the treated thermoplastic network into the interlaminar region of the composite material. Finally, composite laminates made using the FIT technology have both excellent impact resistance and superior in-plane and thickness conductivity. The traditional in-situ toughening sacrifices the good fluidity and prepreg paving performance of thermosetting resin to a certain extent, so that the thermosetting resin can not meet new process requirements.

The invention has the beneficial effects that:

the carbon fiber composite material prepared by the preparation method of the invention overcomes the technical problem that the traditional in-situ toughening can not meet the new process requirements. The invention adopts polypropylene (PP) non-woven fabric and polyether sulfone (PES) film with better toughness as interlayer materials, simultaneously loads multi-wall Carbon Nanotubes (CNTs) in the interlayer materials, then inserts the obtained interlayer materials into carbon fiber/epoxy resin (CF/EP) prepreg, and obtains the carbon fiber composite material by a hot die pressing method.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are included to explain the illustrative embodiments of the invention and the description of the invention and are not intended to limit the invention unduly.

FIG. 1 is a schematic view of the process of the present invention.

Fig. 2 is a graph comparing the conductivity of each sample.

FIG. 3 is a diagram of type I cracking process.

Fig. 4 is a schematic and geometric dimensions of a DCB sample.

FIG. 5 is a graph of a type I crack test.

FIG. 6 is a graph of displacement versus Δ R/R0 during type I cracking for various samples.

FIG. 7 is a graph comparing the load-displacement curves for type I cracks in different sandwich composite materials.

FIG. 8 is a schematic and a geometric plot of an ENF sample.

FIG. 9 is a graph of a type II crack test.

FIG. 10 is a graph of displacement versus Δ R/R0 during type II cracking for various samples.

Figure 11 is a graph of giic values for different sandwich composites.

FIG. 12 is a scanning electron microscope image of type I fracture surfaces of different sandwich composite materials, wherein (a, b) is a blank control; (c, d) PP non-woven fabric; (e, f) containing 10mg/m ² CNTs PP nonwoven.

FIG. 13 is a scanning electron microscope image of type I fracture surfaces of different sandwich composite materials: (a, b) PES film; (c, d) PES film containing 5% by weight of CNTs; (e, f) PES film containing 10wt% CNTs.

FIG. 14 is G for different sandwich composites _IC -a profile.

FIG. 15 shows G for different sandwich composites _IC And G _IR Compare the graphs.

FIG. 16 is a load-displacement curve of the ENF experiment of the same sandwich composite material.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

The present invention will be further described with reference to the following examples and drawings, but the scope of the present invention is not limited in any way.

The purity of the multi-wall carbon nano tube used in the embodiment is more than 91 percent, the inner diameter is 3-5nm, the outer diameter is 8-15nm, and the length is 3-12 mu m; the C15000 unidirectional weftless carbon fiber-epoxy resin prepreg consists of 63wt% of TR50S15L carbon fiber and 37wt% of YPH-308 epoxy resin; polypropylene (PP) non-woven fabric surface density of 15g/m ² And the thickness is 40 mu m. The experimental materials are detailed in table 1, and the experimental devices are detailed in table 2.

Table 1 table of experimental materials

TABLE 2 Experimental equipments

Example 1

A preparation method of a carbon fiber composite material comprises the following steps (the preparation process is shown in figure 1):

(1) Preparation of the Sandwich Material

The surface density of the PP non-woven fabric sandwich material is 15g/m ² And the thickness is 40 mu m, and the rectangular plate is cut into a rectangle with the size of 25mm multiplied by 100mm according to the requirements of subsequent tests. The carbon nanotube-loaded PP non-woven fabric is obtained by a solution spraying method, 0.025g of CNTs are weighed, and the CNTs are dispersed in 5mL of C ₂ H ₅ In OH, firstly stirring for 30min by a magnetic stirrer, then treating for 30min by an ultrasonic stirrer, then uniformly spraying the uniformly dispersed CNTs absolute ethyl alcohol solution on PP non-woven fabric with the thickness of 25mm multiplied by 100mm by a spray can, setting the temperature of an oven at 40 ℃, drying for 30min, and waiting for C ₂ H ₅ The load of 10mg/m is obtained after OH is completely volatilized ² CNTs PP nonwoven sandwich material.

(2) Preparation of composite laminates

Firstly, flatly laying 12 layers of C15000 prepreg in a flat rigid mould cavity along the same fiber direction, then laying the prepared interlayer material, and flatly laying 12 layers of C15000 prepreg with the same size according to the previous laying direction. For a sample used for interlaminar toughness test, a polytetrafluoroethylene film with the thickness of 25 microns needs to be paved at one end of a middle layer sample in the direction perpendicular to a fiber to serve as a prefabricated crack, the prefabricated cracks of a test sample of the I-type interlaminar fracture toughness and a test sample of the II-type interlaminar fracture toughness are respectively 70mm and 40mm in consideration of specific test requirements, and the prefabricated crack is not needed for a sample used for conductivity test.

Closing the mold, heating, curing for 30min at the temperature of 80 ℃ under the pressure of 0.6MPa, keeping the pressure unchanged, continuously heating to 130 ℃, keeping the temperature for 90min, stopping heating, cooling to room temperature, and demolding to obtain the carbon fiber composite material.

Example 2

A preparation method of a carbon fiber composite material comprises the following steps:

(1) Preparation of the Sandwich Material

The membrane material used in this example was prepared by solution casting method, using a 100 × 150mm glass dish as the membrane forming container, weighing 0.03g of CNTs to disperse in 30ml of DMF, magnetic stirring at 50 ℃ for 10min and then ultrasonic stirring for 30min to disperse the CNTs uniformly in the solvent, pouring 0.6g of PES particles into the dispersion, magnetic stirring at 70 ℃ for 90min and then ultrasonic stirring for 60min to completely dissolve PES, pouring the mixture into the glass dish rapidly, and drying in an oven at 120 ℃ for 3h to obtain a CNTs sPES membrane containing 5wt% respectively.

(2) Preparation of carbon fiber composite material

The preparation method is the same as that of example 1.

Example 3

(1) Preparation of the Sandwich Material

The interlayer material was prepared substantially the same as in example 2, except that 0.06g of CNTs was weighed, and a PES film containing 10wt% CNTs was obtained.

(2) Preparation of carbon fiber composite material

The preparation method is the same as that of example 1.

Example 4

A method for preparing a carbon fiber composite material, which is the same as that in example 1, except that the interlayer material in this example is a PP nonwoven fabric.

Example 5

A method for preparing a carbon fiber composite material, which is the same as the method in example 2, except that the interlayer material in this example is a PES film without CNTs added.

Example 6

A carbon fiber composite material was prepared in the same manner as in example 1, except that the interlayer material was not laid.

The thicknesses of the interlayer materials prepared in examples 1-5 are shown in Table 3.

TABLE 3 thickness of the interlayer Material

(I) conducting Performance test

The superiority and inferiority of the conductive properties of the composite material were mainly demonstrated by the conductivity in the thickness direction, and for the composite material having PES films, PES films containing 5wt% CNTs and PES films containing 10wt% CNTs as interlayers, the change in the resistance values during type I and type II cracking was also tested, further showing the effect of different interlayers on the conductive properties of the carbon fiber composite material.

The resistance value in the thickness direction was measured by a digital precision multimeter. 3 rectangular test pieces 20mm long and 20mm wide for resistance value test were cut from the laminate without pre-cracking, and after the cutting was completed, the upper and lower surfaces of the test pieces were polished with sandpaper, wiped with alcohol, placed in an oven for drying, and after completely dried, the specific dimensions of each test piece were measured and numbered as shown in Table 4 (unit: mm). When testing the resistance R, coating a layer of conductive silver paste on the surface of a sample and standing for 1min so as to reduce the contact resistance as much as possible, pressing the upper and lower surfaces of the sample by a torque wrench by using copper plates as electrodes, clamping a positive chuck and a negative chuck on an extended aluminum foil, and reading after the number is stable. The volume conductivity σ in the thickness direction is calculated by equation (1):

wherein h is the thickness of the sample, R is the resistance measured in the thickness direction, and S is the cross-sectional area of the sample in the thickness direction.

TABLE 4 sample size

Polishing the upper and lower surfaces of the junction of the preformed crack and the interlayer material of the sample by using abrasive paper, wherein the junction of the sample for the I-type cracking test is approximately positioned at the position 70mm of the end, the junction of the sample for the II-type cracking test is approximately positioned at the position 40mm of the end, after polishing is finished, the upper and lower surfaces of the sample are wiped clean by absorbent cotton soaked in absolute ethyl alcohol so as to prevent chips from influencing the viscosity of the conductive adhesive, then the sample is put into an oven to be completely dried, the conductive adhesive is uniformly mixed and coated on the upper and lower surfaces of the junction, a copper wire which is about 15cm long is vertically pressed on the conductive adhesive along the fiber direction, a layer of conductive adhesive is further covered on the copper wire, the copper wire is fixed by using a clamp, and the conductive adhesive is completely cured after standing for 6 hours at room temperature. During testing, the two chucks are clamped on the upper copper wire and the lower copper wire respectively, a universal testing machine is used for counting, counting is stopped after testing is finished, the chucks are taken down, and data are exported for subsequent processing. The test results are shown in fig. 2.

(II) measurement of type I fracture toughness

The test was carried out in a universal tester using the double cantilever bending test method (DCB), the test specimen (shown in FIG. 4) was 150mm long and 25mm wide, a 70mm long pre-crack had been made in one end of the specimen using a 25 μm thick Teflon film, and two hinges were attached to the pre-crack end of each specimen, as shown in FIG. 3. This experiment uses AB super glue fixed hinge, for guaranteeing to glue the intensity, AB glue will solidify more than 3 hours at least, the hinge surface will be polished with abrasive paper, thereby make it press from both sides more firmly on the general purpose testing machine, in order to observe the extension and the removal of crackle intuitively, scribble white coating in the side of every sample before the test, 10mm marks in the side with perpendicular fine rule every 1mm before the prefabricated crack back, later every 5mm mark is once, for the ease of observing the extension of crackle, place the magnifying glass of a tape light before the experimental facilities.

The method adopts a displacement control loading mode, the loading rate is 1mm/min, in order to eliminate the influence of stress concentration, before testing, an initial load is applied to a sample to generate a new pre-crack with the length of about 5mm, loading is stopped and the sample returns, then the displacement load is continuously applied, when a new crack is generated, the data of displacement and load is recorded once when the crack with the length of about 1mm is newly generated at the first 5mm, then the data of the displacement load is recorded once when the crack with the length of about 5mm is newly generated until a new crack with the length of about 55mm is generated, loading and returning are stopped, data are exported, and the total crack length is the sum of the distance from the load to the pre-crack end point and the crack propagation length. The experimental procedure is shown in fig. 5. The type i fracture toughness of the laminate is calculated according to formula (2):

where P is the load, δ is the load point displacement, a is the total crack length, b is the specimen width, | Δ | is the abscissa with a,

the image is the cross-sectional distance on the abscissa for the ordinate. The experimental results are shown in fig. 6 and 7.

Measurement of type (III) fracture toughness

The three-point bending test was performed on a universal tester by using the method of end notch bending test (ENF), and the sample size for the test was 25mm x 140mm, and the pre-crack length was 40mm, as shown in FIG. 8. To visually observe the crack propagation and movement, the sides of each sample were painted with a white paint before testing, and the sides were marked with vertical thin lines every 1mm 10mm before the crack was preformed. The mark was then made every 5mm and a lighted magnifying glass was placed in front of each sample in order to facilitate observation of crack propagation.

The test adopts a displacement control loading mode, the loading rate is 1mm/min, in order to eliminate the influence of the tail concentrated stress of the prefabricated crack, the pre-cracking is firstly carried out, the span of a support is adjusted to be 70mm, a loading head is positioned in the middle of the support and is parallel to the support, one end of the support is positioned 25mm in front of the tail of the prefabricated crack, an experimental machine is started, when the crack expands to about 5mm, the loading is stopped and the test is carried out, then the span is adjusted to be 100mm, one end of the support is moved to the position 25mm in front of the pre-crack, the displacement load is continuously applied, when a new crack is generated, the data of the displacement and the load is recorded once when the crack of 1mm is newly generated in the front 5mm, then the data of the displacement load is recorded once when the crack of 5mm is newly generated, the loading and the data are stopped and carried out when the load-displacement curve starts to rise for a section again, the data are derived, and the total crack length is the distance from a loading line to the end point of the pre-crack plus the crack. The experimental procedure is shown in fig. 9. Type ii fracture toughness of the laminate is calculated according to formula (3):

/>

p is the load, δ is the load point displacement, a is the total crack length, 2L is the span, and W is the specimen width. The results of the experiment are shown in FIGS. 10 and 11.

(IV) surface topography characterization

The scanning electron microscope is used for observing the fine structure of the fracture surface of a sample after the type I fracture toughness test and the type II fracture toughness test, and the electron microscope photo helps to analyze the appearance of the fracture surface so as to better explain an experimental result and improve a test scheme. The results of the experiment are shown in FIGS. 12 and 13.

Results and analysis of the experiments

1. As can be seen from fig. 2, after PPNWF and PES films were inserted into the laminate, the conductivity in the thickness direction decreased by 98.6% and 98%, respectively, the conductivity was improved after CNTs was added, the conductivity in the Z direction was improved by 24 times after CNTs was doped with 5wt% into PES films, and the conductivity decreased by 94.7% as compared to the control after the content of CNTs was increased to 10wt%.

2. As can be seen from FIG. 2, the rate of change in resistance during type I cracking was also significantly increased after intercalation, with a PES film containing 10wt% CNT as the interlayer material, the rate of change in resistance was at most 206.9% higher than that of the blank control, and with a PES film as the interlayer material, the rate was at most 145.6% higher.

3. DCB test results (FIGS. 6 and 7) showed that PES films containing 5wt% CNTs had the best effect of improving the toughness of the type I cracks, G _ⅠC The value reaches 0.621KJ/m ² Corresponding to an increase of 178.5%, G _ⅠR The value reaches 0.67KJ/m ² And the improvement is 207 percent. Increasing the content of CNTs to 10wt%, G _ⅠC And G _ⅠR All show a different degree of decline.

4. The ENF test results showed (as shown in FIGS. 10 and 11) that the PES film doped with 10wt% of CNTs had the best effect of improving the toughness of the crack of the layer II, G _ⅡC The value is improved by 37 percent compared with that of a blank control group.

5. As shown in fig. 12 and fig. 13, fig. 12 (a, b) is a cross-sectional profile of a comparison sample, and it can be seen that the interlaminar failure mainly includes interfacial failure between the fibers and the epoxy resin and fracture of the epoxy resin matrix, the fracture surface is smooth, only a few resins are adhered, the fibers can be easily pulled out of the matrix, the interfacial bonding is not firm, and a typical brittle fracture failure mode is presented. Fig. 12 (c, d) is a cross-sectional view of the PPNWF as the interlayer, and it can be seen that the shape and distribution of the PP fibers are similar to their initial state in the nonwoven fabric, most of the PP fibers are completely stripped from the epoxy resin, and only a few parts of the PP fibers are plastically deformed or broken, which indicates that the interfacial interaction between the PP fibers and the epoxy resin is very weak, and the main mechanism of the composite material interlayer breakage is the failure of the weak interface between the PP fibers and the epoxy resin, and from the data analysis before, even if only such a weak interface failure form is added, the type i fracture toughness is improved by 124%, which proves that the potential of the nonwoven fabric for improving the interlayer toughness is very large. FIG. 12 (e, f) is a cross-sectional view of CNTs/PPNWF as an interlayer, it can be easily found that the agglomeration of CNTs is serious, and the weak interface of CNTs makes the adhesion of PP fiber and epoxy matrix poor, which is not beneficial to inhibiting the crack propagation, so that the type I fracture toughness of the composite material does not increase or decrease after the CNTs are added, but it can also be seen from the figure that many new toughening modes, such as plastic deformation, bridging cracks, PP fiber fracture and the like, appear after the CNTs are added, and these new modes can increase the resistance when the cracks propagate and absorb the fracture energy, and it can also be seen that some white CNTs particles are coated on the surface of PP fiber, increasing the surface roughness of the fiber. Therefore, the type I fracture toughness of the laminated plate can be further improved theoretically by adopting a proper dispersion method and controlling the amount of the CNTs to reduce the agglomeration as much as possible.

FIG. 13 (a, b) is the cross-sectional morphology of the PES film as a sandwich, and it can be seen in the low magnification image a that the cross-sectional surface is very rough, some small convex PES films are adhered to the substrate surface, the smooth structure is significantly improved, and it is confirmed that there is a large interfacial force between the film and the epoxy resin, so that the plastic deformation of the film can absorb more fracture energy under the action of stress. Meanwhile, the protruding part plays a role in hindering crack propagation, more energy is consumed to promote crack deflection, and the interlayer fracture toughness is increased. FIG. 13 (c, d) is a cross-sectional topography doped with 5wt% CNTs showing an enlarged image of the interface between the film and the epoxy matrix from which a distinct phase separated structure can be observed, and d is a graph in which the fractures of the film and the epoxy matrix exhibit an irregular morphology indicating that the resin will penetrate into the film during curing to form a nanoscale phase separated structure, increasing the fracture toughness of the matrix while maintaining its original mechanical properties, while also showing villous CNTs at the edges of the structure, indicating that multi-walled carbon nanotubes bond well to the matrix, causing more energy to be consumed in pulling the CNTs out of the matrix during stretching, and further that the pulled-out multi-walled carbon nanotubes exhibit a bridging effect with the fibers and matrix that increases the interlaminar fracture toughness by increasing resistance to crack propagation. FIG. 13 (e, f) is a sectional view of a PES film doped with 10wt% CNTs, in which phase separation structure and fluffy carbon nanotubes can be seen, but it is also difficult to find that compared with an SEM image doped with 5wt% CNTs, the PES film doped with 10wt% CNTs has uneven distribution, and has a relatively serious agglomeration phenomenon, and a weaker interface thereof can reduce the ability to inhibit crack propagation, and such a negative effect caused by the agglomeration exceeds even the positive effect caused by the bridging effect, resulting in a decrease in fracture toughness, but still better than that of the blank control group.

6. Toughness (G) of I-type layer crack of each laminate obtained by calculation _ⅠC ) The changes with crack propagation are shown in fig. 3-6. G of most samples except individual samples _ⅠC The values all float up and down around a constant value, the larger the float taking the average value, which is indicated by the dash-dot line in the figure. From FIG. 14, the G of the respective sandwich material can be seen _ⅠC The values are improved compared with the blank control group, which shows that the toughness of the composite material is improved by adding the interlayer on the whole, the reduction of the critical load is compensated by the improvement of the crack opening displacement, and FIG. 14a shows that G is G when the PP non-woven fabric is used as the interlayer material _ⅠC The value is increased by 124%, after adding CNTs, G _ⅠC The value is reduced to a certain extent, which is consistent with the change rule of critical load, further research can be carried out by reducing the amount of the loaded CNTs, and from FIG. 14b, the PES film serving as an interlayer has the advantages that the I-type layer fracture toughness is improved by 43.8 percent, and the G is doped with 5wt percent of CNTs _ⅠC The value is further improved by 93.6 percent, and G is obtained after the content of CNTs is continuously increased to 10wt percent _ⅠC Instead, the value of (c) is decreased, with the same trend as the critical load.

7. Initial interlaminar fracture toughness (G) of composite materials _IC ) And interlaminar fracture resistance (G) _IR ) As shown in fig. 15. G _IC Representing the interlaminar fracture toughness at a crack length of 55mm,G _IR represents the average value of the interlaminar fracture toughness at a crack length of 65-85 mm. It can be seen that the toughness value of the laminate is highest when the PES film containing 5wt% CNTs as a interlayer is used as compared with other samples, G _IC And G _IR Estimated to be 0.621KJ/m ² And 0.670KJ/m ² 178% and 208% (0.223 KJ/m, respectively) higher than the control sample ² And 0.217KJ/m ² ). It is concluded that when the loading of CNTs is 5wt%, the interface between the prepreg matrix and the PES film bonds well, allowing the multi-walled carbon nanotubes to disperse uniformly, thereby improving the interlaminar toughness.

8. Fig. 16 shows a typical ENF test load-displacement curve, similar to type i cracking, in the initial stage of loading, the curve changes linearly until reaching the maximum load point, at which time the crack starts to initiate, the curve decreases rapidly, and then the load value starts to increase slowly as the crack continues to grow, and it can be seen that after PES interlayer is added to the laminate, the critical load value of the crack is increased by 9.75% compared to the blank control, and after 5wt cnts are doped, the critical load value is greatly decreased, which is decreased by 40% compared to the pure PES film, which is noteworthy because the pre-crack of the laminate sample is shifted, resulting in uneven stress during bending, and the crack finally extends to the sample surface.

The fracture toughness can be deduced by combining data analysis and electron microscope pictures to be related to the interface bonding condition of a CF/EP system and an interlayer material, and more energy is consumed by cracks in the growth process along with the enhancement of the interface bonding force, so that the fracture toughness is improved. In summary, these findings improve the conductive-mechanical properties of the carbon fiber composite material, and place hopes for the carbon fiber composite material to be applied to higher-end fields.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A preparation method of a FIT-based carbon fiber composite material is characterized by comprising the following steps:

(1) Preparation of interlayer material: mixing CNTs and PES particles in a solvent, and drying to prepare a PES film containing the CNTs; or, loading CNTs on a PP non-woven fabric to prepare a CNTs-loaded PP non-woven fabric interlayer material;

(2) Laying carbon fiber/epoxy resin prepreg in the same fiber direction in a mold cavity, laying the interlayer material on the carbon fiber/epoxy resin prepreg, and then laying the carbon fiber/epoxy resin prepreg flatly according to the previous laying direction; and closing the mold, heating, curing at a proper temperature and pressure, stopping heating, cooling to room temperature, and demolding to obtain the carbon fiber composite material.

2. The preparation method of claim 1, wherein CNTs are added into a solvent to be uniformly dispersed to obtain a dispersion, PES particles are poured into the dispersion to completely dissolve PES, and then the PES particles are poured into a glass dish and dried to obtain a PES film containing CNTs; or, uniformly dispersing the CNTs in a solvent, uniformly spraying the CNTs solution on the PP non-woven fabric, and drying to volatilize the solvent to obtain the CNTs-loaded PP non-woven fabric interlayer material.

3. The method according to claim 2, wherein in the step (1), the solvent is DMF or ethanol.

4. The preparation method of claim 1, wherein the CNTs are loaded in the interlayer material of the PP non-woven fabric loaded with the CNTs, and the loading amount of the CNTs is 1-20mg/m ² Preferably 10mg/m ² (ii) a The amount of CNTs in the PES film containing CNTs is 5-10wt%.

5. The method of claim 1, wherein the PES film loaded with CNTs is prepared at a drying temperature of 120 ℃ for a drying time of 3 hours.

6. The preparation method of claim 1, wherein the drying temperature is 40 ℃ and the drying time is 30min when preparing the CNTs-loaded PP non-woven fabric interlayer material.

7. The method according to claim 1, wherein the number of the carbon fiber/epoxy resin prepregs laid twice is 5 to 20, preferably 12.

8. The method according to claim 1, wherein in the step (2), the curing conditions are as follows: curing for 30min under the conditions of 0.6MPa and 80 ℃, keeping the pressure unchanged, continuously heating to 130 ℃, and preserving the heat for 90min.

9. The method according to claim 1, wherein the density of the PP nonwoven fabric surface is 15g/m ² And the thickness is 40 mu m.

10. Carbon fiber composite material obtained by the production method according to any one of the preceding claims.