CN110982225B

CN110982225B - Prepreg and preparation method thereof

Info

Publication number: CN110982225B
Application number: CN201911218732.7A
Authority: CN
Inventors: 欧秋仁; 唐中华; 董大为; 张帅; 陈哲明
Original assignee: Aerospace Research Institute of Materials and Processing Technology
Current assignee: Aerospace Research Institute of Materials and Processing Technology
Priority date: 2019-12-03
Filing date: 2019-12-03
Publication date: 2022-03-04
Anticipated expiration: 2039-12-03
Also published as: CN110982225A

Abstract

The invention provides a prepreg and a preparation method thereof, wherein the prepreg is prepared from a resin matrix and fibers by a hot melting process, the prepreg is composed of an upper soaking layer, a lower soaking layer and a middle partial soaking layer, the middle partial soaking layer is composed of a discontinuous non-soaking fiber area and a soaking fiber area, and the soaking degree of the prepreg is 70-90%. The prepreg which is completely infiltrated up and down and partially infiltrated in the middle is characterized in that the dry fibers are left in the prepreg, so that the same paving property of the prepreg and the conventional prepreg can be ensured, the surface state of the prepreg does not need to be particularly distinguished during paving, the paving manufacturability is good, and the construction is convenient.

Description

Prepreg and preparation method thereof

Technical Field

The invention relates to a prepreg and a preparation method thereof, in particular to the prepreg suitable for an OOA (non-autoclave) process and the preparation method thereof, belonging to the technical field of prepreg preparation.

Background

The resin-based composite material has the characteristics of high specific strength and high specific modulus, so that the resin-based composite material is widely applied to aerospace, along with the gradual increase of the using amount of the composite material and the size of a product, the defects of high equipment investment, high process cost and inconvenience for integrated integral forming of the traditional autoclave and die pressing forming process are increasingly revealed, the requirements of low-cost manufacturing and integrated integral forming of high-performance composite material products cannot be met, and the further expansion and application of the composite material are hindered. Liquid molding represented by VARI has great advantages in low-cost manufacturing and integrated integral molding, but the composite material product manufactured by the liquid molding has low fiber volume content and poor performance, and cannot meet the requirement of the aerospace field on high-performance composite materials. The traditional double-sided impregnated prepreg prepared by the existing hot melting method process is not suitable for a non-autoclave OOA process, gas cannot be smoothly discharged during molding, so that defects in the composite material are caused, the porosity is as high as 5-20%, and the mechanical property of the composite material is poor.

In order to solve the problems, a partially soaked prepreg of a single-sided resin adhesive film exists in the early stage, although the partially soaked prepreg meets the non-autoclave OOA process of a high-performance composite material, the dry fibers are left on the surface of the prepreg, so that the paving performance of one side with the dry fibers is poor, the position of the surface of the dry fibers needs to be paid special attention during paving, and otherwise, errors are easy to occur to cause product scrap.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides the prepreg which is easy to lay and is suitable for the OOA process and capable of improving the qualification rate of the composite material and the preparation method thereof.

The technical solution of the invention is as follows: a prepreg is prepared from a resin matrix and fibers by a hot-melt process, and comprises an upper wetting layer, a lower wetting layer and a middle partial wetting layer, wherein the middle partial wetting layer comprises a discontinuous non-wetting fiber area and a wetting fiber area.

A prepreg is prepared from the fibres containing nano fibresOr functional fillersThe resin matrix and the fibers are prepared by a hot-melt process, the prepreg consists of an upper soaking layer, a lower soaking layer and a middle partial soaking layer, and the middle partial soaking layer consists of a discontinuous non-soaking fiber area and a soaking fiber area; nano-fiberOr functional fillersThe addition amount is not less than 0.5 percent of the mass of the resin matrix.

A prepreg preparation method is realized by the following steps:

firstly, preparing a resin matrix for prepreg and fibers;

and step two, preparing the prepreg by adopting the resin matrix prepared in the step one and a fiber hot melting method, wherein the wettability of the prepreg is 70-90%.

A preparation method of a prepreg is realized by the following steps:

first, preparing the nanofiber-containingOr functional fillersThe addition amount of the nano-fiber is not less than 0.5 percent of the mass of the resin matrix;

the second step, using the nanofibers containing prepared in the first stepOr functional fillersThe resin matrix and the fiber are prepared into the prepreg by the hot melting method, and the prepreg is soakedThe degree of wetness is 70-90%.

Compared with the prior art, the invention has the beneficial effects that:

(1) according to the prepreg which is completely infiltrated up and down and partially infiltrated in the middle, the dry fibers are left in the prepreg, so that the same paving performance of the prepreg and the conventional prepreg can be ensured, the surface state of the prepreg does not need to be particularly distinguished during paving, the paving manufacturability is good, and the construction is convenient;

(2) the partially infiltrated prepreg has the dry fibers inside the prepreg serving as an air guide channel, so that the gas in the prepreg can be discharged under vacuum pressure, the inside of the composite material is densified, and a composite material product with good internal quality is obtained under lower molding pressure;

(3) the invention has small equipment investment and low comprehensive manufacturing cost, and the adoption of the partially infiltrated prepreg of the invention does not need an autoclave and a hot press with expensive investment, has small equipment investment, does not need high energy consumption and high metal molds of the autoclave, and has low comprehensive manufacturing cost;

(4) when the prepreg with self-bonding capability is used for preparing the sandwich material, the weight reduction efficiency is higher, the material cost is saved, a structural adhesive film is not required to be added between the composite material panel and the core material or the resin content of the prepreg is not required to be increased, and the high-bonding-strength sandwich structure composite material can be obtained only by adopting the prepreg with normal resin content, so that the adhesive film is saved or the resin consumption is reduced, the material cost is reduced, and the product weight is further reduced.

Drawings

FIG. 1 is a schematic view of a prepreg structure according to the present invention;

FIG. 2 is a process flow diagram of the present invention.

Detailed Description

The present invention will be described in detail with reference to the following examples and accompanying drawings.

The invention provides a prepreg which is prepared from a resin matrix and fibers by a hot-melt process, and the prepreg comprises an upper wetting layer, a lower wetting layer and a middle partial wetting layer, wherein the middle partial wetting layer comprises a discontinuous non-wetting fiber area and a wetting fiber area.

The invention controls the content of non-infiltrating fibers by controlling the temperature and pressure during prepreg forming, thereby meeting the requirement on the wettability of the prepreg. The wettability is required to be 70-90%, and the wettability refers to the percentage of the fiber content of the impregnating resin in the total fiber content. The discontinuous non-wetting fiber area accounts for 40-60% of the wetting layer of the middle part, and the wetting layer of the middle part accounts for 1/3-1/2 of the total amount of the prepreg.

When the prepreg is prepared by adopting the double-layer resin film, the temperature and the pressure in the hot melting process are controlled, so that only part of the fibers in the middle part are soaked by the resin matrix, the non-soaked fiber areas are reserved, the upper part and the lower part of the prepreg are soaking layers, the fibers are completely soaked by the resin matrix, the same paving manufacturability as that of the common conventional prepreg is ensured, the fibers are partially soaked by the resin matrix in the middle part, the soaked fibers provide rigidity when the prepreg is paved, the non-soaked fibers serve as air guide channels, the gas in the composite material can be smoothly discharged when the prepreg is paved, and the densified composite material can be obtained even under the vacuum pressure.

When the invention adopts the double-layer resin film to prepare the prepreg, in order to obtain a proper partial wetting layer in the middle, the viscosity of the resin matrix and the composite pressure of the prepreg are controlled to realize the preparation, and a person skilled in the art can select the required composite temperature and pressure according to the required wetting quality of the invention.

Further preferably, when the resin matrix and the fibers are compounded into the prepreg, it is more important to select a proper compounding temperature, preferably, the viscosity of the resin matrix at the compounding temperature is between 15000mpa.s and 30000mpa.s, and the compounding pressure is adjusted at the same time, so that the resin matrix is only in a 70% -90% partial infiltration state on the fibers, thereby achieving the microstructure effect shown in fig. 1. The change of the viscosity in the optimal range of the invention has little influence on the subsequent composite material molding, the change can be ignored, the pressure is properly adjusted according to the wettability of the prepreg, and finally the wettability of the prepreg is taken as the core measuring index of the invention. Within the range of the wettability required by the invention, under the same condition, the adjustment of the wettability has little influence on the performance of subsequent products and can be ignored.

If the composite temperature is not properly selected, partial impregnation of the prepreg required by the wettability of the prepreg is difficult to achieve through adjustment of the composite pressure, if the composite temperature is too low, the viscosity of a resin matrix is too high during compounding and is far higher than the optimal range of the invention, the resin wettability is poor, the adjustable space of the composite pressure is small within the adjustable pressure range of prepreg equipment, the manufacturability is poor, too many dry fibers in the middle of the prepreg are easily caused in the prepreg preparation process, and the spreadability of the prepreg is too poor and has no practicability; if the compounding temperature is too high, the viscosity of the resin matrix is too low during compounding and is far below the preferable range of the invention, and the resin matrix can completely soak the fibers under very low compounding pressure, so that no dry fiber area exists in the prepreg, the prepreg becomes the completely soaked prepreg, and in the subsequent composite material forming process, the gas in the composite material cannot be smoothly discharged, so that the composite material meeting the internal quality requirement cannot be prepared, and the method cannot be applied to the OOA process.

The invention has no special requirement on the type of the resin matrix, and the type of the resin matrix is selected according to the performance requirement of the composite material, and can be any resin type which can meet the requirement of preparing the prepreg by a hot melting method, such as epoxy resin, bismaleimide resin, cyanate resin and the like.

The fiber adopted by the invention is continuous fiber, has no special requirements on the type and the form of the fiber, and is selected according to the performance requirement of the composite material. The fiber type can be one or a mixture of several of glass fiber, carbon fiber, aramid fiber and the like, and the fiber form can be unidirectional fiber, plain weave fabric, twill weave fabric, satin weave fabric and the like.

The resin matrix and fiber content in the prepreg of the invention is a known technology for preparing the prepreg by a hot-melt method, and can be adjusted by a person skilled in the art according to production requirements. Generally, the mass percent of the continuous fibers is 55-75 wt%, and the mass percent of the resin matrix is 25-45 wt%. When the fiber is a unidirectional fiber, the preferable proportion of the fiber is 65-70% and the resin matrix is 30-35%; the fiber is a fiber fabric, preferably 60-65% of the fiber and 35-40% of the resin matrix. The resin matrix of the present invention refers to all other materials except carbon fibers, including curing agents and other necessary auxiliaries.

One of the common forms of composite materials is a sandwich structure composite material, which generally comprises a composite panel with upper and lower surfaces and a sandwich layer in the middle, in order to ensure the bonding strength between the composite panel and the sandwich layer, one of the common processing forms is to lay a glue film between the composite panel and the sandwich layer, and although the glue film laying manner can ensure the bonding strength between the panel and the core layer, the material cost and the structure weight of the sandwich structure can be increased. Another method to improve the bonding strength of the face sheet to the core is to increase the resin content of the prepreg in contact with the core and to bond the core with excess resin from the prepreg surface, which also increases the material cost and the structural weight of the sandwich structure.

Aiming at the problem, the invention also provides the prepreg with the self-bonding capability, a structural adhesive film is not required to be added between the composite material panel and the core material or the resin content of the prepreg is not required to be increased, and the high-bonding-strength sandwich structure composite material can be obtained only by adopting the prepreg with the normal resin content, so that the adhesive film can be saved, the resin consumption can be reduced, the material cost can be reduced, and the product weight can be further reduced.

The prepreg with the self-bonding capability is prepared from a resin matrix containing nano fibers and fibers by adopting a hot melting process, and consists of an upper wetting layer, a lower wetting layer and a middle partial wetting layer, wherein the middle partial wetting layer consists of a discontinuous non-wetting fiber area and a wetting fiber area; the addition amount of the nano-fiber is not less than 0.5 percent of the mass of the resin matrix, and the wettability is required to be 70 to 90 percent. The discontinuous non-wetting fiber area accounts for 40-60% of the wetting layer of the middle part, and the wetting layer of the middle part accounts for 1/3-1/2 of the total amount of the prepreg.

The invention adopts the nano-fiber to realize the main function of high-strength bonding of the composite material panel and the core material under the condition of normal resin content of the prepreg. In the process of preparing the sandwich structure composite material, the resin in the prepreg climbs along the thickness direction of the core material under the action of the capillary effect on the surface of the core material to drive the nano fibers in the resin to be oriented along the thickness direction of the core material on the surface of the core material, so that the self-adhesion of the composite material panel to the core material is realized, and the sandwich structure composite material with light weight and high strength adhesion characteristics is obtained.

If the addition of the nano-fiber reaches 0.5 percent of the mass of the resin matrix, a bridging effect can be formed between the composite panel and the core layer, the bonding strength of the panel and the core layer is improved, and the sandwich structure can be damaged in the core layer but not in the bonding interface of the panel and the core layer during flat drawing. The addition amount of the nano-fiber needs to consider the manufacturability after addition, if the addition amount is too large, the nano-fiber is more difficult to disperse uniformly, the agglomeration problem is easy to occur, generally not more than 10%, and the skilled person can select the appropriate addition amount according to the actual production requirement.

The type and content of the resin matrix (including nanofibers) and the type, content and form of the fibers in the prepreg having self-adhesive ability are the same as those described above. When the nanofiber-added resin matrix and the fibers are combined to form a prepreg, an appropriate combination temperature is selected, and the viscosity of the nanofiber-added resin matrix at the combination temperature is preferably set to be between 15000mpa.s and 30000 mpa.s.

The prepreg with self-bonding capability has no special requirements on the type of the nano-fiber, and the proper type can be selected according to the material performance, and can be carbon nano-fiber, titanium oxide nano-fiber or nano-whisker and the like. The preferable length-diameter ratio of the nanofibers is 1000-10000, the preferable diameter of the nanofibers is 30-50 nanometers, the further preferable length-diameter ratio is 3000-7000, and the addition amount of the nanofibers is 1-5% of the mass of the resin matrix.

The length-diameter ratio of the nanofibers cannot be too small, if the length-diameter ratio of the nanofibers is less than 500, the nanofibers are too small, a bridging effect is difficult to form between the composite material panel and the core layer, and if the length-diameter ratio is too large, the problems of too much fiber aggregation and difficult dispersion exist. Within the preferred range of the invention, the overall effect is optimal.

According to the inspiration of the invention, various functional fillers can be added into the resin matrix for preparing the partially-infiltrated prepreg according to the performance requirement of the composite material, so as to obtain the partially-infiltrated prepreg with special function.

Further, the present invention provides a prepreg manufacturing method as shown in fig. 2, which is implemented by the following steps:

1. preparing a resin matrix for prepreg and fibers;

determining the type and content of a resin matrix and the type, content and form of fibers according to production requirements, wherein the resin matrix comprises a curing agent and an accelerant, adding an auxiliary agent into resin, stirring uniformly and defoaming to obtain the resin matrix for the prepreg, and performing conventional surface treatment on the fibers for later use.

2. And (3) preparing the prepreg by adopting the resin matrix prepared in the step (1) and a fiber hot melting method.

In the step, the prepreg compounding temperature is preferably selected to ensure that the viscosity of the resin matrix at the temperature is 15000 mPa.s-30000 mPa.s, and the compounding pressure is required to ensure that the prepreg meets the requirement of 70-90% of wettability. The prepreg prepared by the hot melting method is compounded on the existing prepreg production equipment, and other processes can be adjusted according to actual conditions.

Furthermore, the invention also provides a preparation method of the prepreg with self-adhesive capacity, which is realized by the following steps:

1. preparing a resin matrix for prepreg containing nanofibers and fibers;

according to production requirements, determining the type and content of the resin matrix, the type, content and form of the fiber, and determining the type, size and content of the nanofiber. Adding the nano-fibers into resin, uniformly mixing to obtain a nano-fiber master batch, adding auxiliaries such as a curing agent and an accelerant into the nano-fiber master batch, uniformly stirring and defoaming to obtain a resin matrix for the prepreg containing the nano-fibers, and performing conventional surface treatment on the fibers for later use.

2. And (2) preparing the prepreg by adopting the nanofiber-containing resin matrix prepared in the step (1) and a fiber hot melting method.

In the step, the prepreg compounding temperature is preferably selected to ensure that the viscosity of the resin matrix containing the nano-fibers is 15000 mPa.s-30000 mPa.s at the temperature. The composite pressure must ensure that the prepreg meets the 70-90% wettability requirement.

Example 1

Prepreg preparation:

65-68 wt% of T700 continuous carbon fiber

3068 resin 32-35 wt%

The impregnation degree of the prepreg is 70-75%

The compounding temperature of the prepared prepreg is 65 ℃, the viscosity of the resin is 21000mPa.s, and the compounding pressure is adjusted according to the wettability of the prepreg.

The prepreg prepared in the example is prepared into the composite material by adopting an OOA preparation process, which specifically comprises the following steps:

1. and (6) blanking.

16 layers of 320 x 320mm 0 ° prepreg were cut with an automatic cutting machine.

2. And (6) layering.

And paving a first layer of prepreg on the surface of the mould, packaging by using a vacuum bag, and vacuumizing and pre-compacting at room temperature for 15 min. And then, each time three layers of prepregs are laid, packaging the prepregs by using a vacuum bag, vacuumizing and pre-compacting at room temperature for 15min until all the prepregs are laid, and all prepreg fibers are arranged along one direction.

3. And (4) pre-compacting.

And packaging the laid prepreg layer by using a vacuum bag, continuously vacuumizing and pre-compacting for 2h at room temperature, and exhausting gas wrapped in the prepreg layer.

4. And (4) pre-curing.

And curing the pre-compacted prepreg paving layer at 65 ℃ for 8h to harden the resin to complete the pre-curing of the composite material.

5. And (5) post-curing.

Directly and continuously heating to 130 ℃ to fully solidify the resin, cooling to below 60 ℃, and demoulding to obtain the high-performance composite material flat plate.

The flexural properties, interlaminar shear strength and porosity of the composite materials prepared are shown in Table 1.

Example 2

Prepreg preparation:

65-68 wt% of T700 continuous carbon fiber

3180 32-35 wt% of resin

The impregnation degree of the prepreg is 75-80%

The compounding temperature of the prepared prepreg is 75 ℃, the viscosity of the resin is 28000mPa.s, and the compounding pressure is adjusted according to the wettability of the prepreg.

The prepreg prepared in the example is prepared into a composite material by adopting an OOA preparation process, the precuring temperature of the composite material during the preparation of the OOA is 90 ℃, the post-curing temperature is 180 ℃, and the bending property, the interlaminar shear strength and the porosity of the prepared composite material are shown in Table 1 in the same way as in example 1.

Example 3

Prepreg preparation:

65-68 wt% of T700 continuous carbon fiber

9306 bismaleimide resin 32-35 wt%

The impregnation degree of the prepreg is 80-85%

The compounding temperature of the prepared prepreg is 75 ℃, the viscosity of the resin is 25000mPa.s, and the compounding pressure is adjusted according to the wettability of the prepreg.

The prepreg prepared in the example is prepared into a composite material by adopting an OOA preparation process, the precuring temperature of the composite material during the preparation of the OOA is 100 ℃, the post-curing temperature is 200 ℃, and the bending property, the interlaminar shear strength and the porosity of the prepared composite material are shown in Table 1 in the same way as in example 1.

Example 4

Prepreg preparation:

the compounding temperature of the prepared prepreg is 85 ℃, the viscosity of the resin is 25000mPa.s, and the compounding pressure is adjusted according to the wettability of the prepreg.

The prepreg prepared in this example was prepared into a composite material by using an OOA preparation process, which was the same as that in example 3, and the bending properties, interlaminar shear strength, and porosity of the prepared composite material were as shown in table 1.

Example 5

Prepreg preparation:

PMI foam sandwich structural composites, PMI foam (density 71 kg/m) were prepared using the prepregs of this example³) The thickness is 2 mm.

The OOA process is adopted as follows:

1. 3068 the epoxy resin is cured at moderate temperature for preparing prepreg.

Weighing a certain amount of carbon nano tubes and 3068 medium-temperature curing epoxy resin, primarily mixing the materials by using a stirrer until no dry powder exists, and pouring the mixture into a three-roll grinder to grind for 3-5 times to obtain the carbon nano fiber master batch. According to the requirements of prepreg production on the resin process and the nanofiber content in the resin, proportionally adding a curing agent, an accelerant and a nanofiber master batch into a reaction kettle, and uniformly stirring and defoaming to obtain the resin for the prepreg.

2. Preparing T300-3000-40B twill carbon cloth/3068 resin prepreg.

The prepreg contains 35-38 wt% of resin containing carbon nano tubes 3068. The temperature of the press roll is controlled to be 75 ℃ during compounding, the viscosity of the resin is about 28000mPa.s, and the pressure is adjusted to control the wettability of the prepreg to be 80-90%, so that the resin is prevented from excessively wetting the fibers, the internal quality of the composite material panel is prevented from being affected, and the bonding quality of the panel and the core material is prevented.

3. 320 x 1mm thick face ply.

Cutting 10 layers of prepreg with the size of 320 x 320mm, paving and pasting 5 layers of prepreg required by the upper panel and the lower panel of the composite material together, wherein in the paving and pasting process of the prepreg, each time 3 layers of prepreg are paved, the paving layer needs to be packaged by a vacuum bag, and vacuumizing and pre-compacting are carried out for 10-15min so as to ensure that gas mixed between the paving layers is smoothly discharged.

4. PMI foam sandwich structure composite material encapsulation.

Sequentially placing a T300-3000-40B twill carbon cloth/3068 resin composite material lower panel, a PMI foam material and a T300-3000-40B twill carbon cloth/3068 resin composite material upper panel which are pre-compacted after the laying layers are laid on a flat plate mould, then laying a non-porous isolating film and an air-permeable felt on the surface of the upper panel, and then packaging the components together by using a vacuum bag.

5. PMI foam sandwich structure composite material pre-compaction and carbon nanotube orientation.

Vacuumizing the packaged composite material component with the sandwich structure at room temperature for 2h, further discharging gas mixed in the prepreg and air in an interlayer in the sandwich structure, then preserving heat at 75 ℃ for 4h, gradually impregnating non-soaked continuous fibers and fabrics in the prepreg with resin at low viscosity, densifying a composite material panel, simultaneously wetting and spreading the resin on the surface of a core material to form a glioma under the action of vacuum pressure and the surface capillary effect of the interlayer, and orienting the nanofibers in the resin along the thickness of the core material.

6. Curing the PMI foam sandwich structure composite material.

And (3) preserving the heat of the PMI foam sandwich structure composite material subjected to pre-compaction and carbon nanotube orientation for 2h at 130 ℃, curing the sandwich structure composite material, cooling, and demolding to obtain the sandwich structure composite material.

The flat tensile strength and areal density of the PMI foam sandwich structural composites are shown in Table 2.

Example 6

Prepreg preparation:

the preparation process of the foam sandwich structure composite material is the same as that of example 5, and the flat tensile strength and the surface density of the PMI foam sandwich structure composite material are shown in Table 2.

Example 7

Prepreg preparation:

the aramid paper honeycomb sandwich structure composite material adopts aramid honeycomb density (29 kg/m)³) The thickness is 2mm, the preparation process of the aramid paper honeycomb sandwich structure composite material is the same as that of the embodiment 5, and the difference between the embodiment and the embodiment 5 is that:

and 5, pre-compacting the honeycomb sandwich structure composite material and orienting the carbon nano tubes.

Vacuumizing the packaged composite material component with the sandwich structure at room temperature for 2h, further discharging gas mixed in the prepreg and air in an interlayer in the sandwich structure, then preserving heat at 90 ℃ for 4h, gradually impregnating non-soaked continuous fibers and fabrics in the prepreg with resin at low viscosity, densifying a composite material panel, simultaneously wetting and spreading the resin on the surface of a core material to form nodules by the resin in the prepreg under the action of vacuum pressure and the capillary effect on the surface of the interlayer, and enabling the nano fibers in the resin to be along the thickness direction of the core material.

And 6, curing the honeycomb sandwich structure composite material. And (3) preserving the heat of the honeycomb sandwich structure composite material subjected to pre-compaction and carbon nanotube orientation for 2h at 130 ℃, solidifying the sandwich structure composite material, cooling, and demolding to obtain the sandwich structure composite material.

The flat tensile strength and the areal density of the honeycomb sandwich structure composite material are shown in table 2.

Example 8

Prepreg preparation:

the preparation process of the aramid paper honeycomb sandwich structure composite material is the same as that of example 7, and the flat tensile strength and the surface density of the honeycomb sandwich structure composite material are shown in table 2.

Example 9

Prepreg preparation:

Example 10

Prepreg preparation:

Comparative example 1

Double-layer fully-impregnated prepreg:

65-68 wt% of T700 continuous carbon fiber

9306 resin 32-35 wt%

The wetting degree of the prepreg is 100%

The compounding temperature of the prepared prepreg is 100 ℃, the viscosity of the resin is 10000mPa.s, and the compounding pressure can enable the prepreg to be completely soaked at the temperature of 100 ℃.

The prepreg prepared by the comparative example is prepared into the composite material by adopting an OOA preparation process, the precuring temperature of the composite material is 100 ℃ during the preparation of the OOA, the post-curing temperature is 200 ℃, and the bending property, the interlaminar shear strength and the porosity of the prepared composite material are shown in Table 1 in the same way as in example 1.

Comparative example 2

Single-layer partial impregnation of prepreg:

65-68 wt% of T700 continuous carbon fiber

9306 bismaleimide resin 32-35 wt%

The compounding temperature of the prepared prepreg is 100 ℃, and the viscosity of the resin is 10000 mPa.s. The composite pressure is adjusted to enable the resin to just penetrate through the prepreg from one side of the prepreg to the surface of the other side, and the surface has about 5-15% of dry fibers.

The prepreg prepared by the comparative example is used for preparing the composite material by adopting an OOA process, the precuring temperature of the composite material during the preparation of the OOA is 100 ℃, the post-curing temperature is 200 ℃, and the bending property, the interlaminar shear strength and the porosity of the prepared composite material are shown in the table 1 in the other same examples 1.

TABLE 1

As can be seen from Table 1, the OOA process is adopted for the conventional fully-impregnated prepreg and the single-layer prepreg, and compared with the OOA process adopted for the partially-impregnated prepreg of the invention, the bending property and the interlaminar shear strength of the composite material are greatly reduced, the porosity is greatly increased, and the internal quality of the composite material is obviously deteriorated.

Comparative example 3

The prepreg of this comparative example was prepared in the same manner as in example 5 except that the nanofibers were not added, and the tensile strength and the areal density of the foam sandwich structure composite material were as shown in table 2 in the same manner as in example 5.

Comparative example 4

The prepreg of this comparative example was prepared in the same manner as in example 7 except that the nanofibers were not added, and the foam sandwich structure composite material was prepared in the same manner as in example 7, and the flat tensile strength and the areal density of the sandwich structure composite material were as shown in table 2.

TABLE 2

As can be seen from table 2, in examples 5, 6, 9 and 10, the same foam core material and panel material were used for all of them, compared to comparative example 3, and therefore the areal density was comparable, but the tensile strength and failure mode of the sandwich structure were greatly different, and examples 5 and 6 with nanofibers added were significantly higher than the tensile strength of the comparative example without nanofibers, the failure mode being cohesive failure of the core material in the former case and interfacial failure of the panel and the core material in the latter case.

In example 7 and example 8, compared to comparative example 4, the same honeycomb core material and panel material were used for all three, so the areal density was comparable, but the tensile strength and failure mode of the sandwich structure were very different, and the tensile strength was significantly higher in the example with nanofibers than in the comparative example without nanofibers, the failure mode being cohesive failure of the core material in the former case and interfacial failure of the panel and core material in the latter case.

The invention has not been described in detail and is in part known to those of skill in the art.

Claims

1. A prepreg characterized by: the prepreg is prepared from a resin matrix containing nano fibers and fibers by adopting a hot melting process, the prepreg is composed of an upper soaking layer, a lower soaking layer and a middle partial soaking layer, the middle partial soaking layer is composed of a discontinuous non-soaking fiber area and a soaking fiber area, the soaking degree of the prepreg is 70-90%, the addition amount of the nano fibers is not less than 0.5% of the mass of the resin matrix, and the viscosity of the resin matrix containing the nano fibers is 15000-30000 mPa.s when the prepreg is prepared by adopting the hot melting process.

2. A prepreg according to claim 1, wherein: the discontinuous non-wetting fiber area accounts for 40-60% of the wetting layer of the middle part, and the wetting layer of the middle part accounts for 1/3-1/2 of the total amount of the prepreg.

3. A prepreg according to claim 1, wherein: the length-diameter ratio of the nanofiber is 1000-10000.

4. A prepreg according to claim 3, wherein: the length-diameter ratio of the nano-fibers is 3000-7000, and the addition amount of the nano-fibers is 1-5% of the mass of the resin matrix.

5. A method of making the prepreg of claim 1, by:

firstly, preparing a resin matrix and fibers for a prepreg containing nano fibers, wherein the viscosity of the resin matrix containing the nano fibers is 15000 to 30000mPa.s, and the addition amount of the nano fibers is not less than 0.5 percent of the mass of the resin matrix;

and secondly, preparing a prepreg by adopting the resin matrix containing the nano fibers prepared in the first step and a fiber hot melting method, wherein the prepreg is composed of an upper soaking layer, a lower soaking layer and a middle partial soaking layer, the soaking degree of the prepreg is 70-90%, and the middle partial soaking layer is composed of a discontinuous non-soaking fiber area and a soaking fiber area.

6. The method of manufacturing a prepreg according to claim 5, wherein: the length-diameter ratio of the nanofibers in the first step is 1000-10000.

7. The method of manufacturing a prepreg according to claim 6, wherein: in the first step, the length-diameter ratio of the nano fibers is 3000-7000, and the addition amount of the nano fibers is 1-5% of the mass of the resin matrix.