CN107139506A - A kind of forming method for reducing multiple material part deformation - Google Patents

Abstract

The invention belongs to the field of composite material processing, and in particular relates to a forming method for reducing deformation of composite material parts. The heating and cooling stages of the existing technology generally use a heating and cooling rate of 1-3°C/min. Although it can reduce a certain amount of energy costs, during the entire curing and molding process, due to the factors of the tooling, the furnace temperature surface of the parts and the There is a temperature difference on the die surface. In the heating and cooling stages of the present invention, the heating and cooling rate is 0.5-1.5°C/min, which reduces the difference in heat transfer rate between the part molded surface and the furnace temperature contact surface, and reduces the temperature difference between the furnace temperature surface and the film surface of the part. Keeping the curing time point on both sides of the part consistent can avoid warping and deformation of the part after curing and molding.

Description

A Forming Method for Reducing the Deformation of Composite Parts

Background technique

The invention belongs to the field of composite material processing, and in particular relates to a forming method for reducing deformation of composite material parts.

current technology

Composite parts involve a curing forming process. Now the curing method of parts is generally vacuum bag method. The existing vacuum bag curing molding technology is divided into three stages, heating stage, constant temperature stage, and cooling stage. The curing principle is that the curing equipment transfers the temperature of the heating tube to the air, and then transfers the heat from the air to the parts and tooling. The cooling process is the same, and finally completes the curing process of the parts.

As shown in Figure 1, during the solidification molding process of the vacuum bag method, the part 2 is placed on the molding tool 1, one side of the part 2 is in direct contact with the furnace temperature, and the other side is in contact with the vacuum bag 3. The heating and cooling rates of 1-3°C/min are generally adopted in the heating and cooling stages of the existing technology. Although this method can reduce energy costs to a certain extent, during the entire curing and molding process, due to tooling factors, there is a temperature difference between the furnace temperature surface of the part and the molding surface, and the maximum temperature difference can reach 50°C according to the thermocouple readings.

During the curing and molding process, the furnace temperature surface of part 2 is closer to the furnace temperature, and it reaches the curing critical point before the die-attaching surface in the curing and molding process. The furnace temperature surface of part 2 is ahead of the molding surface at the time of solidification and cooling. After the furnace temperature surface of part 2 is completely solidified and cooled, the molding surface is still in the process of cooling, resulting in internal forces. When fully cured, severe deformation occurs. Through the accumulation of data, the larger the part, the more serious the deformation, and the maximum deformation is about 17mm.

Contents of the invention

The invention optimizes the vacuum bag solidification molding method, reduces the heat transfer rate difference between the furnace temperature surface of the part and the molding surface, reduces the overall temperature difference of the part, and keeps the curing time points on both sides of the part consistent, thereby ensuring the flatness of the part .

A molding method for reducing deformation of composite parts, used for vacuum bag curing molding of composite materials, comprising the following steps:

Step 1. Place the parts on the forming tool, and paste a vacuum bag on the upper end of the part, and place the thermocouple in the thermocouple placement hole of the forming tool;

Step 2, product molding

Push the parts and molding tooling pasted into the vacuum bag into the curing equipment. The heating stage: from room temperature to 180±5°, the heating rate is 0.5-1.5°C/min; constant temperature for 2-2.5 hours; cooling stage: cooling To below 45°, the cooling rate is 0.5-1.5°C/min, and the molding is completed.

For parts with a surface area of more than 1㎡ or with curvature, a constant temperature stage of 80-85°C is added to the heating stage, and the time is 60-75min.

Vacuum test is carried out before curing and molding, and curing is carried out after passing the test.

When approaching the constant temperature phase, the thermocouple reading with temperature lag shall prevail.

Beneficial effects: the present invention reduces the difference in heat transfer rate between the mold-fitting surface of the part and the furnace temperature contact surface, reduces the temperature difference between the furnace temperature surface and the film-attached surface of the part, keeps the curing time points of the two sides of the part consistent, and can avoid the curing of the part Warpage occurs after molding. It is proved by experiments that the final warpage of parts cured and molded by this method is 0-3 mm, which meets various requirements for flatness of composite parts.

Description of drawings

Figure 1 shows the paving structure formed by vacuum bag curing.

detailed description

The first step: Paste the vacuum bag

Place the parts 2 on the molding tool 1, paste the vacuum bag 3, and place the thermocouple 4 in the corresponding thermocouple placement hole.

The second step: product molding

Push the part 2 and the forming tool 1 pasted with the vacuum bag 3 into the curing equipment, and perform curing and molding after the vacuum test is passed. In the heating stage during curing, the temperature is raised from room temperature to 180±5°, the heating rate is 0.5-1.5°C/min; the temperature is kept constant for 2-2.5 hours; then the temperature is lowered to below 45°, the cooling rate is 0.5-1.5°C/min, and the molding is completed .

For parts with a surface area of more than 1㎡ or with curvature, a constant temperature stage of 80-85°C is added to the heating stage, and the time is 60-75min.

When approaching the constant temperature stage, the reading of thermocouple 4 with temperature lag shall prevail.

Claims (4)

1. A molding method that reduces the deformation of composite parts, used for vacuum bag curing molding of composites, characterized in that the method comprises the following steps: Step 1. Place the part (2) on the molding tool (1), and paste a vacuum bag (3) on the upper end of the part (2), and place the thermocouple (4) in the thermocouple placement hole of the molding tool (1) ; Step 2, product molding Push the parts (2) and molding tooling (1) pasted into the vacuum bag (3) into the curing equipment, the heating stage: from room temperature to 180±5°, the heating rate is 0.5-1.5°C/min; constant temperature 2-2.5 hours; cooling stage: cooling to below 45°, the cooling rate is 0.5-1.5°C/min, and the molding is completed. 2. The forming method according to claim 1, characterized in that: for parts with a surface area of more than 1 m2 or with curvature, a constant temperature stage of 80-85°C is added to the heating stage, and the time is 60-75min. 3. The forming method according to claim 1 or 2, characterized in that a vacuum test is carried out before curing and forming, and curing is carried out after passing the test. 4. The molding method according to claim 3, characterized in that: when approaching the constant temperature stage, the thermocouple reading with temperature lag shall prevail.