1. A preparation process of a novel method for toughening fracture toughness between army aircraft structure composite material patch layers is characterized by comprising the following steps:

a: selecting an industrial-grade multi-walled carbon nanotube as a material for toughening interlamination of a patch laminated structure during repair of the composite material;

b: fully vibrating and dispersing the multi-walled carbon nano-tubes in acetone by adopting an ultrasonic dispersion method;

c: spraying the multi-walled carbon nanotubes on the surface of the composite material wet-laid adhesive layer in the step B by using a surface spraying method;

d: and D, paving the wet paving layer prepared in the step C, and curing the wet paving layer and a composite material hot repair instrument (meeting FAA standards).

2. The process for preparing the interlayer fracture toughness of the composite patch with the multi-walled carbon nanotube toughened military aircraft structure according to claim 1, wherein the purity of the multi-walled carbon nanotube in the step A is more than 95 wt%, the inner diameter is 3-5nm, the outer diameter is 8-15nm, and the length range is 3-12 μm.

3. The process for preparing the multi-walled carbon nanotube toughened military aircraft structure composite patch interlayer fracture toughness of claim 1, wherein the ultrasonic dispersion vibration time in the step B is 15 minutes, and the dispersion temperature is 23 ℃.

4. The process for preparing the interlayer fracture toughness of the composite material patch with the multi-walled carbon nanotube toughened military aircraft structure according to claim 1, wherein an air gun with an air source is used for spraying the surface of the composite material wet-paving layer in the step C, the air pressure is 0.2-0.3MPa, and the acetone solution dispersed with the multi-walled carbon nanotube is uniformly sprayed on the surface of the wet-paving layer with the specified area until all required solution is sprayed.

5. The process for preparing the multi-walled carbon nanotube toughened military aircraft structure composite patch interlayer fracture toughness of claim 1, wherein in the step D, the paving and curing are carried out by using a hot-repair instrument at 120 ℃ and 0.1 MPa.

Background

The nano material is directly dissolved in the resin, and then the mixture and the fiber are mixed and integrally hot-pressed and solidified, so that the process is relatively complex, more nano material needs to be added, and the non-interlayer performance of the composite material can be influenced. Chinese patent (CN107459820A) discloses a preparation method of micro-nano particle synergistic interlayer toughening bismaleimide carbon fiber composite material, the method comprises the following steps of obtaining a solid-liquid composite low-viscosity resin system by a 'multiphase composite' method, dispersing thermoplastic microparticles and core-shell nanoparticles in a liquid toughening agent composed of an allyl compound and an epoxy resin, then adding bismaleimide micro powder for uniform premixing, then placing the bismaleimide micro powder on a three-roller grinding machine for physical blending, uniformly dispersing micro-nano particles by virtue of shearing and diffusion effects to obtain a toughened bismaleimide resin system, coating the bismaleimide resin system on a film, and then the prepreg is compounded with a carbon fiber reinforcement body through hot pressing and presoaking, the prepreg which is enriched with multi-scale micro-nano particles on the surface of the reinforcement body and among the fascicles is obtained through the screening and filtering action of fibers, the prepreg is cut and laid in a mold, and the composite material toughened by the micro-nano particles and the interlaminations is obtained through compression molding. The method obtains better interlayer performance, but the process is still more complex, and only G is tested_IC。

Chinese patent (CN104945852A) discloses a micro-nano particle interlayer toughening technology, firstly, a mixed solution of inorganic particles serving as micro-nano particles is uniformly sprayed on fibers, then the fibers are placed in an oven for drying treatment, and the composite material is compounded with thermosetting resin after a solvent is completely volatilized to prepare the micro-nano particle interlayer toughened composite material.

Disclosure of Invention

The invention aims to solve the problem of improving the interlayer fracture toughness of a carbon fiber/resin matrix laminated composite material hot patching instrument process under the condition of an external field during the war of military aircrafts, and provides a preparation method which is suitable for quickly repairing a composite material patch and is suitable for normal hot-pressing curing after the surface of a prepreg is subjected to quantitative and controllable spraying and attaching by using a multi-walled carbon nano tube with lower cost and ultrahigh mechanical property.

A preparation process of a novel method for improving interlayer fracture toughness of a multiwalled carbon nanotube toughened composite material is characterized by comprising the following steps: a: selecting a multi-walled carbon nanotube which is low in cost and easy to obtain as a composite material lamination structure interlayer toughening material, wherein the inner diameter of the multi-walled carbon nanotube is 3-5nm, the outer diameter of the multi-walled carbon nanotube is 8-15nm, the length range of the multi-walled carbon nanotube is 3-12 mu m, and the purity of the multi-walled carbon nanotube is more than 95 wt%; b: fully vibrating and dispersing the multi-walled carbon nano-tubes in an acetone solution by adopting an ultrasonic dispersion method, wherein the vibration time is 15 minutes and the temperature is 23 ℃; c: spraying the multi-walled carbon nanotubes on the surface of the prepreg of the composite material in the step B by using a prepreg surface spraying method, uniformly spraying an acetone solution dispersed with the multi-walled carbon nanotubes on the surface of the prepreg with a specified area by using an air gun with an air source for surface spraying, wherein the air pressure is 0.2-0.3MPa, and till all required solutions are completely sprayed; d: and C, paving and pasting the prepared prepreg in the step C, and curing by using a heat-repair instrument, wherein the curing is carried out by using the temperature of 120 ℃ and the pressure of 0.1 MPa.

The invention utilizes the multi-walled carbon nano-tube with ultrahigh mechanical property to toughen layers, directly carries out surface treatment on the prepreg of the semi-finished product through a simple spray-attaching process, and has normal other process links, thereby greatly simplifying the process and having accurate and controllable spray-attaching density. And a hot patching instrument is utilized for processing, and the method is different from the autoclave process.

The toughened composite material laminated structure prepared by the invention is mechanically processed into a double-cantilever beam DCB sample for testing the change of I-type fracture toughness, and compared with the original composite material structure without any nano material, the effect of the DCB sample is detailed through the comparison of the attached drawings and the following examples.

Drawings

FIG. 1 is a diagram illustrating a process for preparing a sample of the composite material of example 1;

FIG. 2 is a schematic representation of a sample of the DCB composite of example 1;

FIG. 3 is a schematic view illustrating the loading of a sample of the DCB composite of example 1;

Detailed Description

The invention will be better understood from the following examples. However, the contents of the embodiments are described only for illustrating the present invention, and should not be construed as limiting the present invention described in the claims.

Example 1

The multi-walled carbon nanotube toughened T700-3k (manufactured by Nippon Dongli company) epoxy resin-based carbon fiber composite material is characterized by comprising the following steps: (1) selecting an industrial-grade multi-wall carbon nano tube which is low in cost and easy to obtain as a composite material lamination structure interlayer toughening material, wherein the inner diameter of the multi-wall carbon nano tube is 3-5nm, the outer diameter of the multi-wall carbon nano tube is 8-15nm, the length range of the multi-wall carbon nano tube is 3-12 mu m, and the purity of the multi-wall carbon nano tube is more than 95 wt%; (2) fully vibrating and dispersing the multi-walled carbon nano-tubes in acetone by adopting an ultrasonic dispersion method, wherein the vibration time is 15 minutes and the temperature is 23 ℃; (3) spraying the multi-wall carbon nano-tubes in the step (2) on the surface of the wet laying and pasting layer of the composite material by a surface spraying method, wherein the surface spraying density is 1.58g/m²Uniformly spraying an acetone solution dispersed with multi-wall carbon nano tubes on the surface of the prepreg with a specified area by using an air gun with an air source for surface spraying until all required solutions are sprayed; (4) paving and pasting the wet laying layer prepared in the step (3) and curing by a heat-repair instrument, wherein the prepreg curing is carried out at the temperature of 120 ℃ and the pressure of 0.1MPa by the heat-repair instrument; (5) the entire composite board was cut into DCB standard specimens.

TABLE 1 interlaminar fracture toughness of DCB Standard specimens

Toughening material	Example GIC(J/m2)
		Is free of	2.05243
Multiwalled carbon nanotube	4.04748

Table 1 the data illustrates:

example 1 spray-on Process for multiwall carbon nanotubes DCB samples prepared with type I fracture toughness G that is less toughened than the original DCB samples_ICThe improvement is 97.2%.