阅读说明：本技术 一种基于超薄纤维预浸料的高性能碳纤维层合板及其制备方法 (High-performance carbon fiber laminated plate based on ultrathin fiber prepreg and preparation method thereof ) 是由 胡军峰 陈舟 张旭彤 于苏东 王一帆 郭文康 于 2020-05-26 设计创作，主要内容包括：本发明属于复合材料技术领域,具体涉及一种基于超薄纤维预浸料的高性能碳纤维层合板及其制备方法。所述碳纤维层合板包括在与长度方向呈夹角θ的两个方向上铺设的碳纤维,还包括在长度方向上、与长度方向垂直的方向上,或者与长度方向呈夹角θ的两个方向相垂直的两个方向上铺设的碳纤维。本发明通过设计新型铺设结构,提出[±θm/0n]s、[±θm/0n/90n]s、[θm/(90+θ)n/-θm/(90-θ)n]s等新型铺设结构,使碳纤维层合板发生平稳的渐进损伤过程,并增强其在其他方向的承载能力,增强材料的各向承载力及其伪延性；可以通过调整θ的大小,获得在不同方向上具有不同的拉伸强度和伪延性的碳纤维层合板,满足不同的需求；所述碳纤维层合板的制备方法操作简单,便于工业生产。(The invention belongs to the technical field of composite materials, and particularly relates to a high-performance carbon fiber laminated plate based on ultrathin fiber prepreg and a preparation method thereof. The carbon fiber laminated plate comprises carbon fibers laid in two directions forming an included angle theta with the length direction, and further comprises carbon fibers laid in the length direction, the direction perpendicular to the length direction, or the two directions perpendicular to the two directions forming an included angle theta with the length direction. The novel laying structure is designed, and the novel laying structures such as [ + - [ theta ] m/0n ] s, [ + - [ theta ] m/0n/90n ] s, [ theta/(90 + theta) n/-theta m/(90-theta) n ] s and the like are provided, so that the carbon fiber laminated plate is subjected to a stable progressive damage process, the bearing capacity of the carbon fiber laminated plate in other directions is enhanced, and the bearing capacity and the pseudo-ductility of the material in all directions are enhanced; the carbon fiber laminated plate with different tensile strength and pseudo-ductility in different directions can be obtained by adjusting the size of theta, so that different requirements are met; the preparation method of the carbon fiber laminated plate is simple to operate and convenient for industrial production.)

1. The high-performance carbon fiber laminated plate based on the ultrathin fiber prepreg is characterized by comprising carbon fibers laid in two directions forming an included angle theta with the length direction, and carbon fibers laid in the length direction, the direction perpendicular to the length direction or the two directions perpendicular to the two directions forming the included angle theta with the length direction.

2. The ultra-thin fiber prepreg-based high-performance carbon fiber laminate as claimed in claim 1, wherein the ultra-thin layer of carbon fiber prepreg is selected from the carbon fiber laminate and has a thickness of only 0.02mm to 0.06 mm.

3. The ultra-thin fiber prepreg-based high-performance carbon fiber laminate according to claim 1, wherein the carbon fiber laminate has a hybrid structure of high-modulus carbon fiber and low-modulus carbon fiber, and the hybrid combination is interlayer hybrid laying or interlayer hybrid weaving.

4. The ultrathin fiber prepreg-based high-performance carbon fiber laminate as claimed in claim 1, wherein the ultrathin layer carbon fiber prepreg selected for the carbon fiber laminate is mechanically cut to obtain a non-continuous fiber structure, and an included angle between a cut direction and a fiber direction during cutting is α, wherein α is 11.3 °.

5. The ultra-thin fiber prepreg-based high-performance carbon fiber laminate as claimed in claim 4, wherein a part of the incisions are deviated to the left by an angle α from the fiber direction, another part of the incisions are deviated to the right by an angle α from the fiber direction, and the incisions with the same direction are distributed in a staggered manner and in a bidirectional staggered manner.

6. A method for preparing a high-performance carbon fiber laminate based on ultra-thin fiber prepreg according to any one of claims 1 to 5, comprising the steps of:

firstly, placing 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 a designed laying structure;

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

and fourthly, completing high-temperature forming according to a designed forming process, opening a mould, and taking out the composite material to obtain the high-performance carbon fiber laminated plate based on the ultrathin carbon fiber prepreg.

7. The preparation method according to claim 6, wherein in the first step, according to design requirements, a cutting design drawing is guided into a computer, and the carbon fiber prepreg is cut by a numerical control cutting bed.

8. The manufacturing method according to claim 6, wherein in the second step, the release plastic film and the release paper on the two side surfaces of the carbon fiber prepreg are removed when the carbon fiber prepreg is laid.

9. The method according to claim 6, wherein in the second step, the high modulus carbon fiber prepreg and the low modulus carbon fiber prepreg are sequentially laid or a woven product of the high modulus carbon fiber prepreg and the low modulus carbon fiber prepreg is woven according to a designed high modulus carbon fiber-low modulus carbon fiber hybrid composite structure when the carbon fiber prepreg is laid.

10. The method for preparing the rubber mold as claimed in claim 6, wherein in the third step, a suction felt is laid on the surface of the upper mold before the mold is sealed; the operation of sealing the mold includes: sticking a sealing adhesive tape along the edge of the mould; and laying the vacuum bag film on the adhesive absorption felt, gradually removing the isolation paper of the sealing adhesive tape, and tightly attaching the vacuum bag film to the sealing adhesive tape.

Technical Field

The invention belongs to the technical field of composite materials, and particularly relates to a high-performance carbon fiber laminated plate based on ultrathin fiber prepreg and a preparation method thereof.

Background

The new material industry is one of the strategic emerging industries of the country and determines the equipment development level of one country, so the "first generation materials and first generation equipment". Advanced countries such as Europe and America attach great importance to the development of new materials, and specific development plans are proposed, such as German industry 4.0, national nanotechnology plan and material genome plan in the United states. The carbon fiber composite material (CFRP) is used as a novel military and civil dual-purpose material, and is an important guarantee for realizing the development of industries such as aerospace equipment lightweight, accelerated building, energy, traffic and the like.

However, the mutual exclusion of strength and toughness of the conventional carbon fiber composite material is one of the important problems which have long plagued the design field. Although CFRP has the advantages of light weight, high strength, high modulus, etc., its brittle nature and weak residual strength limit its application expansion to some extent. For example, a slight impact may cause a local structural damage inside the CFRP, and at this time, although the CFRP is intact in appearance, it is easy to fracture brittle under a load which is far below the design load without any obvious damage warning, such as a fracture phenomenon of a CFRP wind turbine blade and a bicycle structure. To ensure safety, the maximum allowable stress for CFRP tends to use a greater safety factor than other, more ductile materials. This design limitation not only does not fully exploit the performance advantages of CFRP, but also makes it unsuitable for applications where load conditions are not easily predictable.

Therefore, the material design concept capable of simultaneously enhancing toughness is a long-standing challenge in studying high-performance CFRP, namely how to make CFRP have a nonlinear progressive failure process similar to that of a metal material so that the CFRP has a significant failure early warning phenomenon before final failure, that is, making CFRP change from a brittle failure mode to a pseudo-ductile failure mode, and generating pseudo-ductile strain before CFRP failure fracture, so as to achieve toughness, as shown in fig. 1. In practice, most composite structures are designed as quasi-isotropic laminates of [ + -45 ] ns or [45/0/-45/90] ns to withstand loads in different directions. However, such quasi-isotropic laminates have relatively low elastic modulus and failure stress due to the large fiber lay-up angle. Therefore, researchers have proposed ameliorating this problem by reducing the angle of the fibers to the direction of the load. In view of the excellent performance of the ultrathin carbon fiber prepreg in the aspect of inhibiting damage expansion of the laminate, a tensile experiment is carried out to lay the ultrathin carbon fiber prepreg laminates ([ + -. theta ]5s) at small angles at different angles, and the fact that due to plastic deformation of a matrix material, fibers rotate relative to a load direction is found, as shown in fig. 2, obvious nonlinear stress-strain response is obtained. Wherein the pseudo-ductility strain of the laminated plate with the two types of [ + -25 ]5s and [ + -30 ]5s respectively reaches 1.2% and 2.88%, and simultaneously, the higher longitudinal tensile strength is ensured. (Pseudo-reduction and damage suppression in this ply CFRP angle-plylamnates.J.D.Fuller, M.R.Wisnom.composites: Part A69 (2015) 64-71.)

However, this low angle lay-up structure, while improving the longitudinal strength and modulus and achieving its non-linear mechanical properties due to the fiber direction reconstruction, does not exhibit a smooth progressive damage process due to the absence of multiple breaks of the fibers (see fig. 3c and 3 d). And because the angle is small, the material has weak bearing capacity in other directions and has no false ductility. Therefore, how to improve the laying structure and optimize the design of the fiber angle, so that the angle laying structure material has the nonlinear mechanical response in the stable progressive damage process in different directions, and the pseudo-ductility of the carbon fiber mixed laying structure is improved, which are problems to be solved urgently.

A quick and direct method of increasing the ductility of carbon fiber reinforced composites is to mix other fibers with better ductility with carbon fibers to form a hybrid composite. That is, the matrix contains two or more types of reinforcing fibers, i.e., low elongation fibers (LE) and high elongation fibers (HE). Where the LE fibers are generally broken first and the HE fibers continue to bear in the event the former is broken. The most common hybrid composite structures are in three forms, inter-layer hybrid lay-up, intra-layer hybrid weave, intra-layer fiber mixing, as shown in fig. 4. Generally, carbon fibers belong to LE. After the carbon fiber and other HEs are mixed to prepare the fiber mixed composite material, when the material is failed in stretching, the carbon fiber is firstly broken, and the HE continues to bear external force after the carbon fiber is broken until the carbon fiber is broken, namely the phenomenon of multiple breakage of the fiber occurs. Taking the carbon fiber-glass fiber hybrid composite material as an example, different hybrid composite structures have significant effects on the mechanical properties of the material, and the failure modes occurring when the material fails are also different, as shown in fig. 3. In recent years, due to the continuous development of an ultrathin carbon fiber prepreg process, the excellent mechanical properties of the ultrathin carbon fiber prepreg are reported, and due to the low energy release rate of the ultrathin carbon fiber prepreg, the final failure of the composite material can be delayed by inhibiting the delamination failure and the overall fracture, so that the ultrathin carbon fiber prepreg has higher allowable design strain. However, the current ultrathin carbon fiber prepreg still cannot meet the comprehensive requirements of the strength and toughness of materials in certain fields, such as aerospace, automobile, energy and other industries.

On the other hand, the discontinuous carbon fiber reinforced composite material is prepared by preparing the traditional continuous fiber prepreg into the oriented discontinuous carbon fiber prepreg by a mechanical high-frequency cutting method and curing the oriented discontinuous carbon fiber prepreg. The discontinuous fiber structure improves the material molding flowability and improves the failure characteristic and the energy absorption characteristic of the composite material. However, in all of the conventional non-continuous fiber structures, the strength of the material is weakened by introducing a slit perpendicular to the fiber direction into the prepreg, and the slit is easily broken at a low load level, so that the high strength characteristic of the carbon fiber cannot be fully exerted.

Aiming at the mutual exclusion problem of the strength and the toughness of the CFRP, the invention provides a novel fiber small-angle laying structure, combines the excellent performance of the discontinuous fiber structure in improving the material damage capacity, develops the research of the high-performance pseudo-ductility carbon fiber composite material, and provides a new theoretical and technical support for realizing the design and the application of the high-performance pseudo-ductility carbon fiber composite material.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, and provides a high-performance carbon fiber laminated plate based on ultrathin fiber prepreg, which is designed to overcome the problems that the important practical requirements of the industries such as aerospace, automobiles and energy sources on carbon fiber composite materials and the problems exist in the research on high-performance pseudo-ductility carbon fiber composite materials at the present stage, so that the carbon fiber laminated plate is subjected to a stable progressive damage process, the bearing capacity of the carbon fiber laminated plate in other directions is enhanced, and the all-directional bearing capacity and the pseudo-ductility of the materials are enhanced.

Another object of the present invention is to provide a method for preparing the above high-performance carbon fiber laminate based on the ultra-thin fiber prepreg.

The invention provides a high-performance carbon fiber laminated plate based on an ultrathin fiber prepreg, which comprises carbon fibers laid in two directions (theta direction and theta direction for short) forming an included angle theta with a length direction, and also comprises carbon fibers laid in the length direction (0 degree direction for short), a direction (90 degree direction for short) perpendicular to the length direction, or two directions (theta +90 direction and theta +90 direction for short) perpendicular to the two directions forming an included angle theta with the length direction.

Furthermore, the thickness of the ultrathin carbon fiber prepreg selected for the carbon fiber laminated plate is only 0.02mm-0.06 mm.

Furthermore, the carbon fiber laminated plate has a hybrid structure of high-modulus carbon fiber and low-modulus carbon fiber, and the hybrid combination mode is interlayer hybrid laying or in-layer hybrid weaving.

Further, the ultrathin carbon fiber prepreg selected for the carbon fiber laminated plate is mechanically cut to obtain a non-continuous fiber structure, an included angle between a cut direction and a fiber direction during cutting is alpha, and the alpha is 11.3 degrees.

Furthermore, a part of the incisions and the fiber direction deflect an angle alpha leftwards, the other part of the incisions and the fiber direction deflect an angle alpha rightwards, and the incisions in the same direction are distributed in a staggered manner to form a bidirectional staggered distribution structure. At this time, the incision exhibits two angular changes as viewed from the fiber direction, which may be called a double angle incision, as shown in fig. 5.

The invention also provides a preparation method of the high-performance carbon fiber laminated plate based on the ultrathin fiber prepreg, which comprises the following steps:

firstly, placing 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 a designed laying structure;

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

and fourthly, completing high-temperature forming according to the designed forming process, opening the mould, and taking out the composite material to obtain the high-performance carbon fiber laminated plate based on the ultrathin carbon fiber prepreg.

Further, in the first step, according to design requirements, a cutting design drawing is guided into a computer, and the carbon fiber prepreg is cut through a numerical control cutting bed.

Furthermore, in the second step, the isolation plastic films and release paper on the two side surfaces of the carbon fiber prepreg are removed when the carbon fiber prepreg is laid.

Further, in the second step, when the carbon fiber prepreg is laid, according to the designed high-modulus carbon fiber-low-modulus carbon fiber hybrid composite structure, the high-modulus carbon fiber prepreg and the low-modulus carbon fiber prepreg are successively laid, or a woven product formed by weaving the high-modulus carbon fiber prepreg and the low-modulus carbon fiber prepreg is laid. When the high-modulus carbon fiber prepreg and the low-modulus carbon fiber prepreg are laid firstly and then, the high-modulus carbon fiber and the low-modulus carbon fiber are mixed and laid in an interlayer manner; when a woven product woven by the high-modulus carbon fiber prepreg and the low-modulus carbon fiber prepreg is laid, the high-modulus carbon fiber and the low-modulus carbon fiber are woven in an in-layer mixed manner.

Further, in the third step, before the mold is sealed, the suction felt is laid on the surface of the upper mold. The operation of sealing the mold includes: sticking a sealing adhesive tape along the edge of the mould; and laying the vacuum bag film on the adhesive absorption felt, gradually removing the isolation paper of the sealing adhesive tape, and tightly attaching the vacuum bag film to the sealing adhesive tape.

When the carbon fiber laminated plate with the angle laying structure, namely the carbon fiber laminated plate with the [ +/- [ theta ] n ] s laying structure receives tensile force, the carbon fiber rotates along with the increase of the tensile force, and the carbon fiber is gradually deflected to the 0-degree direction from the +/-theta direction. Fig. 7 shows a fiber rotation phenomenon of the carbon fiber laminate having the [ ± 30]5s lay-up structure. When the carbon fiber rotates, the carbon fiber absorbs energy, so that the material shows certain toughness and generates different strains. The stress strain characteristics and the fiber rotation characteristics of carbon fiber laminates having different lay angles θ are different, as shown in fig. 8. When the carbon fiber rotates, the energy is absorbed and is reflected on the stress strain curve, namely, the curve is not obvious. As shown in fig. 6, from the stress-strain curves of the three carbon fiber laminated sheets having the structures of [ ± 20]5s, [ ± 25]5s, [ ± 40]5s, it can be seen that the carbon fiber laminated sheet is deformed more when stretched as the laying angle θ increases, but the tensile strength thereof is reduced.

The carbon fiber laminate having the [ ±. theta.m/0 n ] s laying structure (wherein m layers of carbon fibers in the theta direction, n layers of carbon fibers in the 0 degree direction and m layers of carbon fibers in the theta direction are laid together in the order of one layer of the theta direction, one layer of the 0 degree direction and one layer of the theta direction, and then m layers of carbon fibers in the theta direction, n layers of carbon fibers in the 0 degree direction and m layers of carbon fibers in the theta direction are laid together in the order of one layer of the theta direction, one layer of the 0 degree direction and one layer of the theta direction) is characterized in that when tensile force is applied, the carbon fibers in the 0 degree direction are firstly broken along with the increase of the tensile force, and then the carbon fibers in the + -theta direction are broken after being rapidly rotated. Multiple breaks in the carbon fibres occur and, in combination with the layered structure failure, a smooth progressive damage process occurs as described in fig. 3c or 3 d.

The carbon fiber laminate having [ ±. thetam/0 n/90n ] s laid structure in which m layers of carbon fibers in the theta direction, n layers of carbon fibers in the 0 ° direction, m layers of carbon fibers in the 0 ° direction, and n layers of carbon fibers in the 90 ° direction are co-laid in the order of one layer of the theta direction, one layer of the 0 ° direction, and one layer of the theta direction, and then n layers of carbon fibers in the 90 ° direction, one layer of the theta direction, m layers of carbon fibers in the theta direction, n layers of carbon fibers in the 0 ° direction, and m layers of carbon fibers in the theta direction are co-laid in the order of one layer of the 90 ° direction, one layer of the 0 ° direction, and one layer of the theta direction, in addition to the multiple breakage phenomenon of carbon fibers similar to the carbon fiber laminate having [ ±. thetam/0 n ] s laid structure, a smooth progressive damage process as shown in fig. 3c occurs because the carbon fibers are introduced in the 90 ° direction (, the tensile strength and modulus in the Y direction are greatly improved. But in the Y direction, no smooth progressive damage process occurs as described in fig. 3c or 3 d.

A carbon fiber laminate having a [ θ m/(90+ θ) n/- θ m/(- θ +90) n ] s lay structure in which m layers of carbon fibers in the θ direction, n layers of carbon fibers in the 90+ θ direction, m layers of carbon fibers in the — θ direction, and n layers of carbon fibers in the- θ +90 direction are co-laid in this order, and then n layers of carbon fibers in the θ +90 direction, m layers of carbon fibers in the θ direction, n layers of carbon fibers in the 90+ θ direction, and m layers of carbon fibers in the θ direction are co-laid in this order, has carbon fibers having different angles from the 0 ° direction. When the carbon fiber is under tension, with the increase of the tension, firstly, the carbon fiber with the minimum included angle with the direction of 0 degree is broken after certain deflection; then, the carbon fiber with the second smallest included angle with the direction of 0 degree is broken after certain deflection is continuously generated; and the like until all the carbon fibers are broken. Multiple breaks of the carbon fibres occur and are more severe, and in combination with the layered structure failure, a smooth progressive damage process occurs as described in fig. 3c or 3 d. Meanwhile, since there is an angle not large from the 90 ° direction (when θ is 25 °, 90+ θ direction is 25 ° from the 90 ° direction), it has mechanical properties and pseudo-ductility characteristics similar to those of the X direction in the Y direction.

After the introduction of the fiber hybrid bond or the discontinuous fiber structure, a more extensive fiber breakage phenomenon is introduced in the carbon fiber laminate, and a smooth progressive damage process occurs as described in fig. 3c or 3 d. So that the pseudo-extensibility characteristic is more remarkable.

The invention has the following beneficial effects:

1. the invention provides novel laying structures such as [ + - [ theta ] m/0n ] s, [ + - [ theta ] m/0n/90n ] s, [ theta/(90 + theta) n/-theta ] m/(-theta +90) n ] s and the like by designing a novel laying structure, so that the carbon fiber laminated plate is subjected to a stable progressive damage process, the bearing capacity of the carbon fiber laminated plate in other directions is enhanced, and the bearing capacity and the pseudo-ductility of the carbon fiber laminated plate in all directions are enhanced;

2. the novel carbon fiber laminated plate with the structure of [ theta/(90 + theta)/(-theta +90) ] ns can obtain carbon fiber laminated plates with different tensile strengths and pseudo-ductility in different directions by adjusting the size of theta, can be suitable for various technical fields, and meets different requirements;

3. the preparation method of the carbon fiber laminated plate is simple to operate and convenient for industrial production.

Drawings

FIG. 1 is a schematic diagram of pseudo-ductility of a carbon fiber laminate;

FIG. 2 is a schematic view of the rotation of the fibers when the carbon fiber laminate is under tension;

fig. 3 is a schematic view of a failure mode and a stress-strain curve of a carbon fiber-glass fiber hybrid composite material: (a) overall fracture, (b) layered fracture, (c) carbon fiber multiple fracture, (d) carbon fiber multiple fracture and layered fracture;

fig. 4 is a graph of three main hybrid composite structures of the hybrid composite: (a) interlaminar mixed laying, (b) intraformational mixed weaving, (c) intraformational fiber mixing

Fig. 5 is a schematic diagram of a discontinuous fiber cut distribution of a carbon fiber prepreg, wherein l is the length of the cut fiber in the fiber direction, d is the length of the cut in the direction perpendicular to the fiber direction, and α is the angle between the cut and the fiber direction (0 ° < α <90 °);

FIG. 6 is a stress-strain curve of three carbon fiber laminates having a structure of [ + -20 ]5s, [ + -25 ]5s, [ + -40 ]5 s: a [ + -20 ]5s, B [ + -25 ]5s, C [ + -40 ]5 s;

FIG. 7 is a rotary perspective view of fibers of a carbon fiber laminate having a [ + -30 ]5s structure

FIG. 8 is a graph showing the effect of different angle lay structures on the stress-strain and fiber rotation performance of laminate: (a) x, y stress strain curves, (b) fiber rotation performance;

FIG. 9 is a schematic view of a partial lay-up according to the present invention;

fig. 10 is a stress-strain curve of the carbon fiber laminate having the structure of [ ± 25/0]5s in example 1 of the present invention.

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 creative effort.