CN105082567A - Curing method for large-thickness fiber-reinforced epoxy resin matrix composite material - Google Patents

Abstract

The invention discloses a curing method for a superlarge-thickness fiber-reinforced epoxy resin matrix composite material and a composite material workpiece manufactured according to the method. Compared with a common constant-speed temperature-rising curing method, the stepped curing method for the superlarge-thickness thermosetting resin matrix composite material has the advantages that the degree of asynchronous curing of the interior of the superlarge-thickness composite material can be greatly lowered, and the temperature uniformity in the curing process of the large-thickness composite material is improved. The curing method is suitable for manufacturing large-thickness composite material parts in fields such as the aviation field, the aerospace field, the building field, the wind power field, the naval ship field, the automobile field and the electronic field.

Description

Curing Method of Large Thickness Fiber Reinforced Epoxy Resin Matrix Composites

technical field

The present invention relates to a method of curing a large thickness fiber reinforced epoxy resin based composite material and a composite material article manufactured according to said method.

technical background

In the process of manufacturing large and complex composite parts, it is necessary to optimize the curing method of large thickness parts. The manufacture of large-thickness composite parts usually has the following problems: due to the low thermal conductivity of polymer materials, the curing cycle of large-thickness composites is longer. During the heating and curing process, there are temperature hysteresis and temperature overshoots inside, which will cause uneven temperature on the thickness gradient and asynchronous curing, which will eventually lead to uneven internal residual stress, fiber volume content and mechanical properties of the part. In extreme cases, excessive temperatures can cause material degradation, carbonization and even composite combustion.

In order to optimize the curing method of large-thickness wallboard and obtain qualified composite parts, relevant scholars have done a lot of research. However, due to the low thermal conductivity, anisotropy and curing exothermic characteristics of epoxy resin-based composite materials, making It becomes difficult and complicated to optimize in common solidification regimes using theoretically derived methods. S.R.White et al. (White, S.R.in'Proc.ICCM-9', UniersityofZaragoza, SpainandWoodheadPublishingCo., Cambirdge, 1993, Vol.3, pp.622-629) then adopts the "step-by-step curing" method that includes multiple insulation steps The curing process was optimized for ultra-thick composite parts, and it was found that the internal quality of the cured part was greatly improved, but the disadvantage of this method is that the cycle is too long, which is more than 6-10 times that of the ordinary cycle. In addition, some manufacturing processes for ultra-thick parts have also been reported, but most of these processes require new types of process equipment, which is not very practical in actual production. How to use existing curing equipment such as autoclaves to manufacture large-thickness composite parts with high efficiency and high quality is the key to solving such problems.

Contents of the invention

The invention proposes the method of slow step heating and step cooling to solidify large-thickness composite material parts. Compared with the usual uniform heating and curing method, the curing method of step heating and step cooling can slow down the concentrated heat release phenomenon in the middle of the large thickness wall plate, and achieve uniform temperature and simultaneous curing in the thickness direction. This method can effectively improve defects such as scorching and void increase caused by curing heat release, and can also reduce the occurrence of micro-cracks and stress concentration inside large-thickness composite materials, thereby obtaining high-quality large-thickness composite materials. pieces.

Compared with the curing method of the present invention for large-thickness epoxy resin-based composite material parts, the manufactured large-thickness composite material parts have better product quality, such as more uniform internal quality , lower porosity and better thickness stability. According to the curing method of the present invention, conventional composite material manufacturing equipment and conditions can be used to obtain high-quality large-thickness composite material products. The method is suitable for manufacturing large-thickness composite material beams, wall panels, ribs, connecting angle pieces, cylindrical, rod-shaped structures, armor, heat insulation structures and other thermosetting composite parts. The method is also applicable to molding processes of fiber-reinforced resin-based composite materials such as thermal molding, autoclave, and RTM molding.

The invention relates to a method for curing a large-thickness fiber-reinforced epoxy resin-based composite material, which is characterized in that it comprises the following steps:

(1) The fiber-reinforced epoxy resin-based prepreg laid up in the mold is heated to the curing temperature of the prepreg with a specific heating step and a specific heating rate;

(2) Carry out insulation curing at the curing temperature;

(3) After the curing is completed, the temperature is lowered to close to room temperature with a specific cooling step and a specific cooling rate, and the entire curing process is completed to obtain a large-thickness composite material part.

According to one embodiment of the present invention, the thickness of the composite material part is in the range of 10-100 mm.

According to one embodiment of the present invention, the curing equipment is any one of heating and curing equipment such as autoclaves, ovens, and hot presses.

According to one embodiment of the present invention, the temperature rise step covers several continuous non-overlapping temperature intervals between room temperature and curing temperature.

According to an embodiment of the present invention, the number of heating steps may be any integer greater than or equal to 2 and less than or equal to 5, preferably 2 or 3.

According to one embodiment of the present invention, the specific optimal heating rate is any fixed rate between 0.1-10°C/min, preferably 0.1-5°C/min, more preferably 0.1-2°C/min.

According to one embodiment of the present invention, only one heating rate is used in one heating step.

According to one embodiment of the present invention, the curing temperature is any fixed temperature between 120-250°C.

According to one embodiment of the present invention, the holding time at the curing temperature is 50-250 minutes, preferably 60-210 minutes.

According to one embodiment of the present invention, the cooling steps are several consecutive non-overlapping temperature intervals covering from the curing temperature to room temperature or below.

According to an embodiment of the present invention, the number of cooling steps may be any integer greater than or equal to 1 and less than or equal to 5, preferably 2 or 3.

According to one embodiment of the present invention, the specific optimized cooling rate is any fixed rate between 0.1-10°C/min, preferably 0.1-5°C/min, more preferably 0.1-2°C/min.

According to one embodiment of the present invention, only one cooling rate is used in a cooling step.

According to one embodiment of the present invention, the fibers of the fiber-reinforced epoxy resin-based composite material may be one or more synthetic fibers, such as carbon fibers, quartz fibers (such as glass fibers), aramid fibers, polypropylene fibers, polypropylene fibers, Benzimidazole fibers, polypropylene fibers, polyimide fibers or their mixtures, etc.

According to an embodiment of the present invention, the fibers of the fiber-reinforced epoxy resin-based composite material may be one or more of chopped fibers, long fibers, continuous fibers, fiber fabrics or fiber mats.

Compared with the usual uniform temperature rising curing method, this method can greatly reduce the degree of asynchronous curing inside the ultra-large thickness composite material, and improve the temperature uniformity in the curing process of the large-thickness composite material. At the same time, it can eliminate the temperature overshoot and scorching caused by the sharp rise in temperature during curing. Therefore, the present invention can effectively improve defects such as internal scorching and increased voids in large-thickness composite materials caused by exothermic curing, and can also reduce the occurrence of micro-cracks and stress concentration inside large-thickness composite materials. The quality of the composite material produced by this method is more excellent than that of the composite material produced by the direct temperature rise curing process. The method involved in the invention is suitable for the manufacture of large-thickness composite material parts in the fields of aviation, aerospace, construction, wind power, ships, automobiles and electronics.

Description of drawings

FIG. 1 shows the ultrasonic detection image of the composite product in Example 11.

Fig. 2 shows an ultrasonic inspection image of a composite product of the present invention.

Comparing Figure 1 and Figure 2, it can be seen that the brightness of the ultrasonic testing image of the composite product of Example 11 is obviously very uneven, indicating that its internal quality is seriously uneven. On the contrary, in Fig. 2, the brightness of the ultrasonic detection image of the composite material product obtained by the method of the present invention is uniform, indicating that its internal quality is also uniform.

Detailed ways

Example 1

On the flat steel mold, the carbon fiber reinforced epoxy resin-based prepreg with a size of 500×500mm is paved, and the paving is completed when the thickness reaches 16mm. Lay the isolation film, air felt and vacuum bag on the prepreg, and stick the vacuum bag on the mold with high temperature resistant adhesive tape, use the vacuum device to draw out the gas in the vacuum bag, and maintain the negative pressure state, when the vacuum bag After the vacuum degree stabilizes, the packaging of the prepreg is completed. Place the encapsulated prepreg in an autoclave, and set the pressure of the autoclave to 0.5MPa. First, in the temperature rise step from room temperature to 90°C, the temperature rises to 90°C at a rate of 2°C/min. Raise the temperature up to 180°C at a rate of 0.1°C/min in the temperature rise step from 90 to 180°C, and keep the temperature at a rate of 2°C/min for 120 minutes and then drop it below 23°C, take out the prepreg to obtain a composite material parts.

Example 2

On the curved aluminum mold, lay carbon fiber plain weave fabric, and when the thickness reaches 60mm, the laying is completed. After heat setting, epoxy resin is injected into the laid fabric by using resin vacuum introduction technology, and after packaging, the fabric is placed in an oven. In the oven, the heating rate is first raised to 90°C at a rate of 0.3°C/min. Use a heating rate of 1°C/min to rise to 110°C, then use a heating rate of 1.5°C/min to rise to 120°C, and keep at this temperature for 120 minutes, then drop to 100°C at a rate of 0.3°C/min, and then use When the speed of 2°C/min is reduced to below 23°C, composite parts with qualified quality can be obtained.

Example 3

On the composite material mold, the aramid fiber-reinforced epoxy resin-based prepreg with a diameter of 1200 mm is paved, and the paving is completed when the thickness reaches 80 mm. Lay the isolation film, air felt and vacuum bag on the prepreg, and stick the vacuum bag on the mold with high temperature resistant adhesive tape, use the vacuum device to draw out the gas in the vacuum bag, and maintain the negative pressure state, when the vacuum bag After the vacuum degree stabilizes, the packaging of the prepreg is completed. Place the packaged prepreg in an autoclave, set the pressure of the autoclave to 0.9MPa, first raise the temperature to 80°C at a rate of 0.1°C/min, and then increase the rate of temperature to 80°C at a rate of 0.5°C/min. 100°C, then rise to 120°C at a rate of 1°C/min, and keep at this temperature for 60 minutes, then drop to 100°C at a rate of 0.1°C/min, and then drop to 23°C at a rate of 0.5°C/min Next, the prepreg is taken out to obtain a composite material product.

Example 4

In the closed mold, inject long carbon fiber-reinforced epoxy resin at a pressure of 0.5 MPa. After the injection is completed, the mold is heated up. The specific heating and cooling process is as follows: firstly, the heating rate is raised to 85°C at a heating rate of 1°C/min, and then raised to 120°C at a heating rate of 1.5°C/min, and then raised to 180°C at a heating rate of 3°C/min. The temperature was kept for 210 minutes, then dropped to 100°C at a rate of 0.5°C/min, and then lowered to below 23°C at a rate of 1°C/min to obtain a composite material part.

Example 5

On a steel spherical mold, a glass fiber-reinforced epoxy resin-based prepreg with a thickness of 80mm is laid. Lay the isolation film, air felt and vacuum bag on the prepreg, and stick the vacuum bag on the mold with high temperature resistant adhesive tape, use the vacuum device to draw out the gas in the vacuum bag, and maintain the negative pressure state, when the vacuum bag After the vacuum degree stabilizes, the packaging of the prepreg is completed. Place the packaged prepreg in an autoclave, set the pressure of the autoclave to 0.5MPa, firstly raise the temperature to 120°C at a rate of 1.5°C/min, and then increase the rate of temperature to 120°C at a rate of 2°C/min. 180°C, then raised to 220°C at a heating rate of 0.5°C/min, and kept at this temperature for 100 minutes, then lowered to 100°C at a rate of 0.3°C/min, and then lowered to 23°C at a rate of 2°C/min Next, the prepreg is taken out to obtain a composite material product.

Example 6

On the flat steel mold, the quartz fiber-reinforced epoxy resin-based prepreg with a size of 350×350mm is paved, and the paving is completed when the thickness reaches 19mm. Lay the isolation film, air felt and vacuum bag on the prepreg, and stick the vacuum bag on the mold with high temperature resistant adhesive tape, use the vacuum device to draw out the gas in the vacuum bag, and maintain the negative pressure state, when the vacuum bag After the vacuum degree stabilizes, the packaging of the prepreg is completed. Place the packaged prepreg in an autoclave, and set the pressure of the autoclave to 0.35MPa. First, in the temperature rise step from room temperature to 120°C, the temperature rises to 120°C at a rate of 1.5°C/min. In the heating step from 120 to 150°C, use a heating rate of 1°C/min to rise to 150°C, and in the heating step from 150 to 180°C, use a heating rate of 0.5°C/minute to rise to 180°C, and keep at this temperature 160 minutes, in the cooling step from curing temperature to 120 °C, drop to 120 °C at a rate of 0.5 °C/min, and then in the cooling step from 120 to 23 °C, use a rate of 1 °C/min to drop below 25 °C, take out the Impregnated to obtain composite parts.

Example 7

On the flat steel mold, the polyethylene fiber-reinforced epoxy resin-based prepreg with a size of 350×350mm is paved, and the paving is completed when the thickness reaches 64mm. Lay the isolation film, air felt and vacuum bag on the prepreg, and stick the vacuum bag on the mold with high temperature resistant adhesive tape, use the vacuum device to draw out the gas in the vacuum bag, and maintain the negative pressure state, when the vacuum bag After the vacuum degree stabilizes, the packaging of the prepreg is completed. Place the encapsulated prepreg in an autoclave, and set the pressure of the autoclave to 0.7MPa. First, in the temperature rise step from room temperature to 120°C, the temperature rises to 120°C at a rate of 2°C/min. In the heating step from 120 to 150°C, use a heating rate of 0.2°C/min to rise to 150°C, and in a heating step from 150 to 180°C, use a heating rate of 0.5°C/minute to rise to 180°C, and keep at this temperature For 150 minutes, drop to 120°C at a rate of 0.5°C/min in the cooling step from curing temperature to 120°C, and then drop to below 23°C at a rate of 2°C/min in the cooling step from 120 to 23°C. Impregnated material, you can get quality composite parts.

Example 8

On the composite mold, lay the glass fiber fabric, and when the thickness reaches 16mm, the laying is completed. After heat setting, use resin impregnation technology to inject epoxy resin into the laid glass fiber fabric. After packaging, place the fabric in an oven. In the oven, first use a heating rate of 0.5°C/min to rise to 100°C. , use a heating rate of 1°C/min to rise to 150°C, then use a heating rate of 1.5°C/min to rise to 180°C, and keep at this temperature for 170 minutes, then drop to 150°C at a rate of 0.5°C/min, then The temperature is lowered to below 23° C. at a rate of 3° C./min to obtain composite material parts.

Example 9

On the curved aluminum mold, the carbon fiber-reinforced epoxy resin-based prepreg with hyperboloid structure is paved, and the paving is completed when the thickness reaches 66mm. Lay the isolation film, air felt and vacuum bag on the prepreg, and stick the vacuum bag on the mold with high temperature resistant adhesive tape, use the vacuum device to draw out the gas in the vacuum bag, and maintain the negative pressure state, when the vacuum bag After the vacuum degree stabilizes, the packaging of the prepreg is completed. Place the packaged prepreg in an autoclave, set the tank pressure of the autoclave to 0.6MPa, first use a heating rate of 0.5°C/min to rise to 80°C, and then use a heating rate of 1.5°C/min to rise to 100 ℃, then use a heating rate of 2℃/min to rise to 120℃, and keep it at this temperature for 200 minutes, then lower it to 100℃ at a speed of 0.3℃/min, and then lower it to below 23℃ at a speed of 0.5℃/min , take out the prepreg to obtain a composite material part.

Example 10

In the closed mold, short glass fiber reinforced epoxy resin is injected at a pressure of 0.3MPa, and after the injection is completed, the temperature of the mold is raised. The specific heating and cooling process is as follows: firstly, the heating rate is raised to 90°C at a heating rate of 1°C/min, and then raised to 120°C at a heating rate of 1.5°C/min, and kept at this temperature for 210 minutes, and then at a rate of 0.5°C/min It is lowered to 100°C, and then lowered to below 23°C at a speed of 1.5°C/min to obtain a composite material part.

Embodiment 11 (comparative example)

On the composite material mold, lay the glass fiber fabric, and when the thickness reaches 32mm, the laying is completed. After heat setting, resin impregnation technology is used to inject epoxy resin into the laid glass fiber fabric. After packaging, the fabric is placed in an oven. In the oven, the heating rate is first raised to 180°C at a rate of 3.0°C/min. , and kept at this temperature for 120 minutes, and then cooled down to room temperature with a cooling rate of 3°C/min to obtain a composite material part. After the ultrasonic testing, the internal quality of the part is seriously uneven, and there are defects such as large voids and delamination, which are unqualified products (see Figure 1). It shows that qualified large-thickness composite parts cannot be obtained by direct heating and cooling process.

It should be noted that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Those skilled in the art understand that any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (17)

1. the curing of heavy thickness fiber reinforced epoxy resin based composites, comprise: epoxy resin-matrix prepreg good for laying is in a mold placed in curing apparatus together with mould, adopt specific intensification ladder number and specific heating rate, ladder-elevating temperature is to the solidification temperature of prepreg; Heat preservation solidification is carried out under this solidification temperature; To be solidified complete after with ladder number and the specific rate of temperature fall of specifically lowering the temperature, ladder is cooled to close to room temperature, completes whole solidification process.

2. method according to claim 1, the fiber of wherein said fiber reinforced epoxy resin based composites is selected from carbon fiber, quartz fibre (preferred glass fibers), aramid fiber, polyethylene fibre PBI fibre, polypropylene fibre, polyimide fiber and their mixture.

3. method according to claim 1 and 2, the fiber of wherein said fiber reinforced epoxy resin based composites can be one or more of chopped strand, long fibre, continuous fiber, fabric or fibrofelt.

4. the method according to any one of claim 1-3, the thickness range of wherein said composite product is 10-100mm.

5. the method according to any one of claim 1-4, wherein said curing apparatus is autoclave, baking oven, hot press are heating and curing in equipment any one.

6. the method according to any one of claim 1-5, is characterized in that: described specific intensification ladder be cover from room temperature to solidification temperature between some continuous nonoverlapping temperature range.

7. method according to claim 6, is characterized in that: the number of described specific intensification ladder can be more than or equal to 2 and be less than or equal to 5 arbitrary integer, preferably 2 or 3.

8. the method according to any one of claim 1-7, is characterized in that: described specific heating rate is any one fixed rate between 0.1-10 DEG C/minute, preferred 0.1-5 DEG C/min, more preferably 0.1-2 DEG C/min.

9. the method according to any one of claim 1-8, is characterized in that: in an intensification ladder, only adopt a kind of heating rate to heat up.

10. the method according to any one of claim 1-9, is characterized in that: described solidification temperature is any fixed temperature between 120-250 DEG C.

11. methods according to any one of claim 1-10, is characterized in that: temperature retention time is at curing temperatures 50-250 minute.

12. methods according to any one of claim 1-11, is characterized in that: described specific cooling ladder be to cover from solidification temperature to a certain lower temperature between some continuous nonoverlapping temperature range.

13. methods according to any one of claim 1-12, is characterized in that: the number of described specific cooling ladder can be more than or equal to 1 and be less than or equal to 5 arbitrary integer, preferably 2 or 3.

14. methods according to any one of claim 1-13, is characterized in that: described specific rate of temperature fall is any one fixed rate between 0.1-10 DEG C/minute, preferred 0.1-5 DEG C/min, more preferably 0.1-2 DEG C/min.

15. methods according to any one of claim 1-14, wherein said solidification is the fiber-reinforced resin matrix compound material forming and hardenings such as hot moulding, autoclave, RTM be shaping.

Heavy thickness fiber reinforced epoxy resin based composites product prepared by 16. methods according to any one of claim 1-15.

17. heavy thickness fiber reinforced epoxy resin based composites products according to claim 16, comprise the heavy thickness same with thermosetting compound material product being selected from composite material beam, wallboard, rib, connection gusset plate, tubular, rod-like structure, plate armour and heat insulation structural.