CN105063684A - Preparing method for surface conducting layer of carbon fiber epoxy resin matrix composite - Google Patents

Abstract

The invention relates to a preparing method for a surface conducting layer of a carbon fiber epoxy resin matrix composite. The preparing method comprises the steps that polishing, oil removing with a thermal alkali solution, surface cleaning with water, micro-etching and neutralizing treating, surface cleaning with water, sensibilizing, surface cleaning with water, activating, surface cleaning with water, electroless copper plating, surface cleaning with water, copper electroplating, surface cleaning with water, electrogilding and the like are carried out on the part, with the conducting layer to be prepared, of the carbon fiber epoxy resin matrix composite. According to the method, mechanical and chemical treatment means are used for removing resin, wrapping carbon fibers, on the part, with the conducting layer to be prepared, of the carbon fiber epoxy resin matrix composite so that the surface carbon fibers can be exposed, sensibilized and activated electroless copper plating is used for improving the binding force between a coating and the carbon fiber resin matrix composite, the preparing efficiency of the conducting layer is improved through copper electroplating, and the corrosion resistance of the conducting layer is improved through electrogilding. The conducting layer prepared through the method has the beneficial effects of being smooth in surface, even, compact, low in resistance, high in binding force, good in corrosion resistance, good in process stability, low in cost and the like.

Description

A method for preparing a conductive layer on the surface of a carbon fiber epoxy resin-based composite material

technical field

The invention belongs to the technical field of material surface treatment, and in particular relates to a method for preparing a conductive layer on the surface of a carbon fiber epoxy resin-based composite material with good bonding force, low resistance and corrosion resistance.

Background technique

Carbon fiber epoxy resin-based composite materials have the advantages of high specific strength and specific modulus, good fatigue resistance, and strong designability, and have been widely used in aerospace, wind power and other fields. However, loads such as lightning strikes and impacts during service will cause damage to the material, reduce its mechanical properties, and threaten structural safety. In addition, since carbon fiber epoxy resin-based composites have certain conductivity, the resistance may change when they are damaged. Therefore, the damage state of the material can be evaluated to a certain extent by monitoring the resistance change in real time. In order to measure the resistance change between monitoring points, it is necessary to prepare a conductive layer on the surface of the composite material connected with the internal fibers. Some researchers use the method of surface coating conductive glue, which has the problems of easy wear of the conductive layer, inaccurate control of thickness, unstable resistance and high cost; some researchers use the method of electroless nickel plating, the disadvantage of which is that the resistance is biased. There are also some researchers who use copper electroplating or electroless copper plating, but there are problems such as easy oxidation of the copper plating surface, low adhesion of electroplating copper plating, and low efficiency of electroless copper plating. Therefore, it is of great significance to invent a method for preparing a conductive layer on the surface of a carbon fiber epoxy resin-based composite material that can simultaneously meet the requirements of low cost, low resistance, corrosion resistance, and high bonding force.

Contents of the invention

In order to solve the above problems, the object of the present invention is to propose a method for preparing a conductive layer on the surface of a carbon fiber epoxy resin-based composite material with high bonding force, good corrosion resistance, low resistance, low cost, good process stability, and environmental protection.

In order to achieve the above object, the preparation method of the surface conductive layer of the carbon fiber epoxy resin composite material provided by the invention comprises the following steps carried out in order:

1) First, the parts on the carbon fiber epoxy resin-based composite material that need to be prepared with a conductive layer are polished with coarse sandpaper and fine sandpaper in sequence until the carbon fibers on the surface of the part are exposed;

2) Use a hot alkali solution at 50-60°C and containing 60g sodium hydroxide, 15g sodium carbonate and 30g sodium phosphate per liter to degrease the above-mentioned polished surface for 20-30 minutes;

3) Clean the above-mentioned degreased surface with water;

4) Treat the part where the conductive layer is to be prepared after cleaning with a 70°C microetching solution for 5-8 minutes, and then treat it with a 50°C neutralizing solution for 3-5 minutes to remove the resin covering the carbon fiber, so that the carbon fiber is exposed to as much as possible surface;

5) Clean the surface after the above treatment with water;

6) Under the temperature of 20～30 ℃, carry out sensitization treatment to the surface after above-mentioned cleaning with the mixed solution of 10g stannous chloride and 10ml hydrochloric acid in every liter for 10～15 minutes;

7) washing the surface after the above-mentioned sensitization treatment with water;

8) at a temperature of 20 to 30°C, use a mixed solution containing 0.5g of palladium chloride and 10ml of concentrated hydrochloric acid per liter to carry out activation treatment on the surface after the above cleaning for 10 to 15 minutes;

9) washing the surface after the above-mentioned activation treatment with water;

10) At a temperature of 68-72°C, use 6-8g anhydrous copper sulfate, 28-32g sodium hypophosphite, 80-85g sodium citrate dihydrate, 29-31g boric acid and 4-6mg2,2 per liter. '-Bipyridyl, the mixed solution with a pH value of 9 to 10 performs electroless copper plating on the surface after cleaning, until the predetermined thickness of the coating is reached;

11) Clean the surface after the above-mentioned electroless copper plating with water;

12) At a temperature of 20-25°C, use 180-240g of anhydrous copper sulfate per liter, 25-50mL of concentrated sulfuric acid with a mass fraction of 98%, 80-100mg of chloride ions, and 0.5-1.0mg of 2-mercaptobenzimidazole , 0.3 ~ 0.8mg ethylene thiourea and 10 ~ 20mg sodium polydithiodipropane sulfonate mixed solution on the surface after the above water cleaning, electroplating copper treatment, the current density is 0.5 ~ 1.5A/dm ² , the coating thickness is 50～300μm;

13) Cleaning the above-mentioned electroplated copper-treated surface with water;

14) At a temperature of 45-50°C, use 9-11g of gold chloride, 78-82g of potassium phosphate, 79-81g of 5,5-dimethylhydantoin, and 0.08-0.12g of butynediol per liter. , 0.09~0.1g sodium saccharin and 9~10mg sodium lauryl sulfate mixed solution to electroplate gold on the surface after electroplating copper treatment, the current density is 1.5~1.8A/dm ² , and the coating thickness is 1~3μm , the pH value is 9-10;

15) Washing the above-mentioned electroplated gold-plated surface with water, thereby obtaining a low-resistance conductive layer on the surface of the carbon fiber epoxy resin-based composite material.

The microetching solution in step 4) contains 60g potassium permanganate and 30g sodium hydroxide per liter, and the neutralization solution contains 28g oxalic acid crystals and 100 milliliters of concentrated sulfuric acid with a mass fraction of 98% per liter.

The thickness of the coating in the step 10) is 1-2 μm.

The preparation method of the surface conductive layer of the carbon fiber epoxy resin-based composite material provided by the present invention is to first utilize mechanical and chemical roughening means to expose the carbon fiber end of the surface of the carbon fiber epoxy resin-based composite material to be prepared for the conductive layer, and then The activation and electroless copper plating process is used to prepare the conductive layer with high bonding force with the carbon fiber and resin matrix, and then the electroplating copper process is used to increase the thickness of the conductive layer, and finally the electroplating gold is used to make the plating layer have better corrosion resistance. The conductive layer prepared by the method has the advantages of low resistance, high binding force, corrosion resistance, low cost, good process stability, high efficiency and the like.

Description of drawings

Figure 1 is a schematic diagram of the structure of the test device for measuring the resistance value by the four-probe method.

Among them: 1: Indenter on the testing machine 2: PTFE plate

3: copper electrode 4: carbon fiber epoxy resin matrix composite material

5: Copper electrode 6: PTFE plate

7: Force sensor 8: Lower pressure head of testing machine

9: Testing machine column

Detailed ways

The method for preparing the surface conductive layer of the carbon fiber epoxy resin-based composite material provided by the present invention will be described in detail below in conjunction with the accompanying drawings and specific examples.

Example 1

The T300/914 carbon fiber epoxy resin composite laminate is selected as the specimen, and the layering method is [(0/90) ₄ ] _s , and the specimen size is 200mm×10mm×2mm. The surface of the above-mentioned T300/914 carbon fiber epoxy resin composite material was polished successively with sandpaper with a particle size of 200, 400, and 600, and then the surface was washed with water and used as a comparison sample for later use.

Example 2

Polish the surface of the above-mentioned T300/914 carbon fiber epoxy resin composite material with sandpaper with a particle size of 200, 400, and 600; The solution was degreased for 30 minutes; then the surface was cleaned with water; the surface of the conductive layer to be prepared after the above cleaning was first treated with a microetching solution containing 60g potassium permanganate and 30g sodium hydroxide per liter at 70°C for 5 minutes, and then used 50 DEG C containing 28g of oxalic acid crystals per liter and 100 milliliters of concentrated sulfuric acid with a mass fraction of 98% for 5 minutes; wash the surface with water; The mixed solution of hydrochloric acid was used to sensitize the cleaned surface for 10 minutes; the surface was washed with water; The surface of the conductive layer was activated for 10 minutes; the surface was cleaned with water; at a temperature of 70°C, 8g of anhydrous copper sulfate, 28g of sodium hypophosphite, 80g of sodium citrate dihydrate, 29g of boric acid and 5mg2 were used per liter. 2'-Bipyridyl, the mixed solution with a pH value of 9 is used to perform electroless copper plating treatment on the surface of the above-mentioned part where the conductive layer is to be prepared for 60 minutes; wash the surface with water; , 30mL mass fraction is the mixed solution of the concentrated sulfuric acid of 98%, 80mg chloride ion, 0.5mg2-mercaptobenzimidazole, 0.3mg ethylene thiourea and 10mg sodium polydithiodipropane sulfonate to prepare conductive layer after above-mentioned cleaning Electroplated copper on the surface, the current density is 1.0A/dm ² , and the electroplating time is 2 hours; the surface is cleaned with water; Methylhydantoin, 0.1g butynediol, 0.1g sodium saccharin and 10mg sodium lauryl sulfate, the mixed solution of pH value is 9 carries out electroplating gold treatment to the surface after above-mentioned electroplating copper treatment, and current density is 1.5A/dm ² , electroplating time is 3 minutes; the above-mentioned electroplated surface is washed with an aqueous solution, thereby obtaining a conductive layer on the surface of the carbon fiber epoxy resin-based composite material.

Example 3

Polish the surface of the above-mentioned T300/914 carbon fiber epoxy resin composite material with sandpaper with a particle size of 200, 400, and 600; The solution was degreased for 20 minutes; then the surface was cleaned with water; the surface of the conductive layer to be prepared after the above cleaning was first treated with a microetching solution containing 60g potassium permanganate and 30g sodium hydroxide per liter at 70°C for 6 minutes, and then used 50 DEG C containing 28g of oxalic acid crystals per liter and 100 milliliters of concentrated sulfuric acid with a mass fraction of 98% for 5 minutes; wash the surface with water; The mixed solution of hydrochloric acid was used to sensitize the cleaned surface for 10 minutes; the surface was washed with water; The surface of the conductive layer was activated for 15 minutes; the surface was cleaned with water; at a temperature of 71°C, 8g of anhydrous copper sulfate, 30g of sodium hypophosphite, 85g of sodium citrate dihydrate, 30g of boric acid and 5mg2 were used per liter. 2'-Bipyridyl, the mixed solution with a pH value of 9 is used to perform electroless copper plating on the surface of the above-mentioned conductive layer to be prepared for 90 minutes; wash the surface with water; , 40mL mass fraction is the mixed solution of the concentrated sulfuric acid of 98%, 80mg chloride ion, 0.5mg2-mercaptobenzimidazole, 0.3mg ethylene thiourea and 10mg sodium polydithiodipropane sulfonate to prepare conductive layer after above-mentioned cleaning Electroplating copper treatment on the surface, the current density is 1.0A/dm ² , and the electroplating time is 1.5 hours; the surface is washed with water; Methylhydantoin, 0.1g butynediol, 0.1g sodium saccharin and 10mg sodium lauryl sulfate, the mixed solution of pH value is 9.5 carries out electroplating gold treatment to the surface after above-mentioned electroplating copper treatment, and current density is 1.6A/dm ² , electroplating time is 2 minutes; the above-mentioned surface after electroplating gold is washed with an aqueous solution, thereby obtaining a conductive layer on the surface of the carbon fiber epoxy resin-based composite material.

Example 4

Polish the surface of the above-mentioned T300/914 carbon fiber epoxy resin composite material with sandpaper with a particle size of 200, 400, and 600; The solution was degreased for 25 minutes; then the surface was cleaned with water; the surface of the conductive layer to be prepared after the above cleaning was first treated with a microetching solution containing 60g potassium permanganate and 30g sodium hydroxide per liter at 70°C for 8 minutes, and then used 50 DEG C containing 28g of oxalic acid crystals per liter and 100 milliliters of concentrated sulfuric acid with a mass fraction of 98% for 5 minutes; wash the surface with water; A mixture of hydrochloric acid was used to sensitize the surface after cleaning for 12 minutes; the surface was washed with water; The surface of the conductive layer was activated for 15 minutes; the surface was cleaned with water; at a temperature of 72°C, 7g of anhydrous copper sulfate, 32g of sodium hypophosphite, 80g of sodium citrate dihydrate, 30g of boric acid and 5mg2 were used per liter. 2'-Bipyridine, the mixed solution with a pH value of 9 is used for 120 minutes to perform electroless copper plating treatment on the surface of the part where the conductive layer is to be prepared; the surface is cleaned with water; , 40mL mass fraction is the mixed solution of the concentrated sulfuric acid of 98%, 90mg chloride ion, 0.5mg2-mercaptobenzimidazole, 0.5mg ethylene thiourea and 12mg sodium polydithiodipropane sulfonate to prepare conductive layer after above-mentioned cleaning Electroplated copper on the surface, the current density is 1.0A/dm ² , and the electroplating time is 2 hours; the surface is cleaned with water; Methylhydantoin, 0.1g butynediol, 0.1g sodium saccharin and 10mg sodium lauryl sulfate, the mixed solution of pH value is 10 carries out electroplating gold treatment to the surface after above-mentioned electroplating copper treatment, and current density is 1.8A/dm ² , electroplating time is 2 minutes; the above-mentioned surface after electroplating gold is washed with an aqueous solution, thereby obtaining a conductive layer on the surface of the carbon fiber epoxy resin-based composite material.

In order to verify the effect of the carbon fiber epoxy resin-based composite material surface conductive layer preparation method provided by the invention, the inventor has carried out the following experiments:

1) Carry out a thermal shock test on the above-mentioned test pieces prepared by Examples 2-4, so as to verify the binding force of the coating. Put the test piece in an electric thermostat with a temperature of 150°C, keep it warm for 1 hour, then quickly put it into a water tank at 10°C for instant cooling, take it out after 10 minutes and blow it dry, and repeat the above process 50 times. The results show that after 50 thermal shock tests, the coating has no cracks or peeling off, indicating that the coating has a high bonding force.

2) In order to verify the corrosion resistance of the conductive layer prepared above, a nitric acid mist test was carried out. Pour 500ml of nitric acid with a mass percentage concentration of 70% into a desiccator with a volume of 9L and let it stand for 30 minutes. Put the prepared test piece with a conductive layer in a 25°C desiccator and let it stand for 75 minutes. The parts were quickly placed in a 125°C high-temperature box for 15 minutes, taken out and cooled to room temperature, and no bulges or corrosion black spots were observed under an optical microscope within 1 hour, indicating that the prepared conductive layer has good corrosion resistance.

3) Use the device shown in FIG. 1 to measure the resistance value of the comparison piece made in the above-mentioned embodiment 1 and the test pieces made in the examples 2-4.

As shown in Figure 1, the measured resistance R _m mainly includes the wire resistance R _L , the sample resistance R _S , the copper electrode resistance _Re and the contact resistance R _c between the carbon fiber epoxy resin matrix composite material and the metal copper electrode. Resistor _RL is negligible, then:

R _m =R _S +R _e +R _c (1)

The sample resistance can be expressed as:

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; \&ap;</span>\frac{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Where ρ _f is the resistivity of the fiber, L _x is the length of the sample, V _f is the fiber volume fraction, _Ly is the width of the sample, and e ₀ is the total thickness of the 0 ⁰ ply. The resistivity of the ToraycaT300 carbon fiber selected in the examples is about 1.7×10 ^-2 Ω·mm, the length of the sample in the fiber direction is 200 mm, the fiber volume fraction is about 0.6, the sample width is 20 mm, and the total thickness of the 0° layup It is about 1.0mm, and the sample resistance R _S is about 0.28Ω from the formula (2). The contact pressure applied by the above test device is 10N, the applied current is 1A, and the electrification time is 5 minutes. As the current action time increases, the temperature of the sample rises, and the resistance of the sample will change at this time. Due to the short energization time, the change in resistance value can be ignored. The resistivity of copper is about 1.7×10 ^-5 Ω·mm, so the resistance R _e of the copper electrode can also be ignored. Therefore, the measured resistance R _m is mainly composed of the specimen resistance R _S and the contact resistance R _c .

After testing, the measured resistance R _m of the comparative sample in Example 1 was 30.68Ω, and the measured resistance R _m after the conductive layer was prepared on the surface in Examples 2-4 was all 0.40Ω. This is due to the fact that the fiber at the contact position with the copper electrode in Example 1 is not fully exposed, and the fiber contact area participating in the conduction is small, so that the measured resistance value is large; and in the preparation process of Examples 2-4, chemical roughening (micro-etching, After the neutralization) treatment, the epoxy resin covering the carbon fiber on the surface of the carbon fiber epoxy resin matrix composite material is removed, the carbon fiber is fully exposed and closely combined with copper through sensitization, activation, electroless copper plating and other processes, and finally forms a layer on the surface The dense conductive layer, the conductive layer is smooth and flat, and the resistivity of copper and gold is very low, so the measured resistance R _m is low and the difference in resistance due to the different thickness of the conductive layer is negligible.

Claims (3)

1. a surface conductive layer preparation method for carbon fiber epoxy based composites, is characterized in that: described surface conductive layer preparation method comprises the following step carried out in order:

1) first will carbon fiber epoxy based composites need the position of preparing conductive layer carry out polishing with flint paper and fine sandpaper successively, until the carbon fiber of this portion faces exposes;

2) with 50 ~ 60 DEG C and in often liter containing the hot alkaline solution of 60g sodium hydroxide, 15g sodium carbonate and 30g sodium phosphate to above-mentioned glazed surface oil removing 20 ~ 30 minutes;

3) surface after above-mentioned oil removing is cleaned with water;

4) first use 70 DEG C of etching solution process 5 ~ 8 minutes to after cleaning for the position of preparing conductive layer, then with 50 DEG C of neutralization solution process 3 ~ 5 minutes to remove the resin of carbon coated fiber, make carbon fiber be exposed to surface as far as possible;

5) surface after above-mentioned process is cleaned with water;

6) at the temperature of 20 ~ 30 DEG C, containing the mixed solution of 10g tin protochloride and 10ml hydrochloric acid, sensitized treatment is carried out 10 ~ 15 minutes to the surface after above-mentioned cleaning with in often liter;

7) surface after above-mentioned sensitized treatment is cleaned with water;

8) at the temperature of 20 ~ 30 DEG C, containing the mixed solution of 0.5g Palladous chloride and 10ml concentrated hydrochloric acid, activation treatment is carried out 10 ~ 15 minutes to the surface after above-mentioned cleaning with in often liter;

9) surface after above-mentioned activation treatment is cleaned with water;

10) at the temperature of 68 ~ 72 DEG C, 6 ~ 8g anhydrous cupric sulfate, 28 ~ 32g inferior sodium phosphate, 80 ~ 85g Sodium Citrate, usp, Dihydrate Powder, 29 ~ 31g boric acid and 4 ~ 6mg2 is contained with in often liter, 2'-dipyridyl, pH value be 9 ~ 10 mixed solution electroless copper process is carried out to the surface after above-mentioned cleaning, until reach predetermined thickness of coating;

11) surface after above-mentioned electroless copper process is cleaned with water;

12) at the temperature of 20 ~ 25 DEG C with in often liter containing 180 ~ 240g anhydrous cupric sulfate, 25 ~ 50mL massfraction be 98% the vitriol oil, 80 ~ 100mg chlorion, 0.5 ~ 1.0mg2-mercaptobenzimidazole, 0.3 ~ 0.8mg ethylene thiourea and 10 ~ 20mg sodium polydithio-dipropyl sulfonate mixed solution electro-coppering process is carried out to the surface after above-mentioned water cleaning, current density is 0.5 ~ 1.5A/dm ², thickness of coating is 50 ~ 300 μm;

13) surface after above-mentioned electro-coppering process is cleaned with water;

14) at the temperature of 45 ~ 50 DEG C, 9 ~ 11g gold trichloride, 78 ~ 82g potassiumphosphate, 79 ~ 81g5 is contained with in often liter, the mixed solution of 5-T10,0.08 ~ 0.12g butynediol, 0.09 ~ 0.1g soluble saccharin and 9 ~ 10mg sodium lauryl sulphate carries out electrogilding process to the surface after above-mentioned electro-coppering process, and current density is 1.5 ~ 1.8A/dm ², thickness of coating is 1 ~ 3 μm, and pH value is 9 ~ 10;

15) clean the surface after above-mentioned electrogilding process with water, obtain low-resistance conductive layer on carbon fiber epoxy based composites surface thus.

2. the surface conductive layer preparation method of carbon fiber epoxy based composites according to claim 1, it is characterized in that: described step 4) in etching solution often rise in containing 60g potassium permanganate and 30g sodium hydroxide, be the vitriol oil of 98% containing 28g oxalic acid crystal and 100 milliliters of massfractions during neutralization solution often rises.

3. carbon fiber epoxy based composites surface conductive layer preparation method according to claim 1, is characterized in that: described step 10) in the thickness of coating be 1 ~ 2 μm.