Automatic thermoplastic composite workpiece laying device and method based on oil heating mold

Abstract

The invention belongs to the technical field of thermoplastic composite material forming preparation, and relates to an automatic thermoplastic composite material part laying device and method based on an oil heating mold. The device comprises a forming mold and a high-heat-conduction oil circulating system, a profiling runner network is integrated in the mold, and the runner layout is dynamically adjusted according to the local curvature radius and is combined with a high-temperature stable material to achieve efficient heat conduction. Through the three-stage process of forced circulation heating of high-thermal-conductivity silicone oil, prepreg laying and gradient cooling, and by dynamically adjusting the oil temperature and the flow speed, the fusion interface bonding and non-isothermal crystallization behaviors are synchronously optimized. The problems of large temperature gradient, dynamic response delay, high energy consumption and the like of a traditional heating scheme are solved, high-precision forming of a complex molded surface workpiece is achieved, the comprehensive energy consumption is low, and an efficient equipment foundation is provided for automatic manufacturing of thermoplastic composite materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermoplastic composite material forming and preparation, and relates to an automatic placement device and method for thermoplastic composite parts based on an oil-heated mold. Background Art

[0002] The automated fiber placement (AFP) technology of thermoplastic composites has become a key process for manufacturing complex components in fields such as aerospace and rail transit due to its advantages of high-efficiency forming and recyclability. However, during the process of layer-by-layer placement of thermoplastic prepregs (such as PAEK / CF, etc.), rapid interlayer diffusion and bonding of molten resin need to be achieved, and its process efficiency is directly limited by the dynamic control ability of the temperature field during the heating-cooling process. In existing heating schemes, although infrared radiation, laser heating, and resistive molds are widely used, there are still significant bottlenecks: (1) Infrared / laser heating relies on surface energy absorption, and it is easy to cause a steep increase in the temperature gradient in the thickness direction due to material transmittance differences and radiation attenuation effects, resulting in insufficient melting at the interlayer interface, inducing an increase in porosity and discrete mechanical properties; (2) The resistive heating mold controls the temperature in zones through embedded electric heating elements, but its heat conduction path is limited by the anisotropy of the mold material, and it is difficult to avoid local heat accumulation or cold zone defects in curved or large-sized molds, and the high energy consumption and low dynamic response characteristics of the electric heating elements further exacerbate the complexity of process regulation; (3) During the rapid cooling stage, the heat capacity of the mold is mismatched with the resin crystallization kinetics, which is likely to cause non-uniform shrinkage and residual stress accumulation, resulting in a decrease in the dimensional accuracy and service stability of the component.

[0003] In response to the above problems, existing technologies mostly use multi-stage hot air assistance or dynamic induction heating for improvement. However, the former is difficult to meet the requirements of high melting temperatures (>350°C) due to low convective heat transfer efficiency, and the latter is limited in industrial applicability due to uneven electromagnetic field distribution and high equipment costs. In addition, although the gradient temperature control strategy based on zone resistance heating can partially improve the temperature field uniformity, its inherent defects of large thermal inertia and slow response are still difficult to adapt to the dynamic thermal requirements of high-frequency start-stop and variable curvature placement in the AFP process.

[0004] Analysis of Existing Patents

[0005] (1) Infrared or laser heating is used to process thermoplastic materials, without considering the problem of uneven temperature in the front and rear regions during heating, and at the same time, the crystallization behavior of the resin during cooling is not controlled;

[0006] (2) There are no relevant patents in existing patents that combine the oil heating method with the automatic placement technology and are applicable to the manufacturing of complex-shaped parts of thermoplastic composites.

[0007] Disadvantages of Current Existing Technologies:

[0008] (1) Heating the material surface by infrared or laser heating easily leads to insufficient melting of the interlayer interface, increasing the interface porosity and affecting the mechanical properties of the workpiece; (2) The traditional heating system lacks an active cooling mechanism, resulting in a mismatch between the mold hot melt and the non-isothermal crystallization kinetics of the resin. The cooling rate is uncontrollable, easily inducing the accumulation of residual stress and causing warping deformation of the workpiece.

[0009] (3) Although technologies such as induction heating can improve the local temperature control accuracy, restricted by the uneven distribution of the electromagnetic field and equipment costs, it is difficult to be applied on a large scale to large-size or complex-curved surface molds. Summary of the Invention

[0010] Objectives of the present invention:

[0011] (1) Through the design of high thermal conductivity oil heat exchange and complex-shaped surface heat conduction pipelines, eliminate the thermal gradient in the thickness direction and ensure the uniformity of heat reception between layers;

[0012] (2) By adjusting the temperature rise and fall rate of the oil temperature and the flow rate of the oil, the crystallization kinetics of the resin during the cooling stage can be controlled, reducing the residual stress of the component and suppressing warping deformation;

[0013] (3) Using the oil heating method for heating and cooling, the design is relatively simple. While being compatible with the geometric characteristics of complex-shaped surface molds, the comprehensive energy consumption is low.

[0014] Technical solution of the present invention: An automatic placement device for thermoplastic composite parts based on an oil heating mold, including a forming mold for complex-shaped surface parts, a high thermal conductivity oil circulation heating system, an automatic placement actuator, and a temperature control module; design a flow channel network inside the forming mold for complex-shaped surface parts that matches the geometric characteristics of the surface of the complex-shaped surface part. The flow channels are distributed in a staggered manner along the normal direction of the mold surface. The height difference between adjacent flow channels is 3 - 5 mm, and the flow channel spacing is adjusted according to the local curvature radius. A serpentine pipe with a diameter of 8 - 12 mm is arranged 8 - 12 mm below the forming mold, with a spacing of 80 - 120 mm, as the high-temperature thermal conductivity silicone oil delivery pipeline; the high thermal conductivity oil circulation heating system includes a high-temperature silicone oil storage tank, a centrifugal pump, and connecting pipes. The centrifugal pump drives the high-temperature silicone oil in the high-temperature silicone oil storage tank to flow through the flow channel network, combined with the gradient temperature control module, to achieve the uniformity of the mold surface temperature; the automatic placement actuator integrates a pressure roller and a tension control unit, with a placement speed of 20 - 260 mm / s, dynamically matching the curvature change path to ensure that the resin melts and can fully diffuse between the prepreg layers.

[0015] The temperature sensor in the temperature control module has an accuracy of ±1°C.

[0016] The temperature fluctuation of the mold surface is ≤±2°C.

[0017] The forming die is made of nickel-based superalloy or Q235 steel, and a three-dimensional profiling runner network is integrated inside it.

[0018] The spacing of the runners is adjusted according to the local curvature radius. When R ≤ 30 mm, it is encrypted to 80 - 100 mm, and when R > 30 mm, it is extended to 100 - 120 mm.

[0019] The pressure of the pressure roller is 100 - 500 N.

[0020] The pressure of the tension control unit is 2 - 5 N.

[0021] In the thermoplastic composite material, the resin is polyaryletherketone resin, and the fiber is high-performance carbon fiber. The melt index of the polyaryletherketone resin is ≥ 90 g / 10 min, and the surface density of the prepreg is 210 g / m 2 。

[0022] A method for using an oil-heated die in the automatic placement process of thermoplastic composite materials includes the following steps:

[0023] (1) Clean the surface of the die. Pass a high thermal conductivity medium into the pipeline through a centrifugal pump at a flow rate of 1.5 L / min, and heat the surface of the die to the melting temperature of the thermoplastic prepreg.

[0024] (2) Use an automatic placement actuator to lay the thermoplastic prepreg tow on the surface of the die, and apply a pressure of 100 - 500 N with a pressure roller to ensure that the prepreg fits the surface of the die, facilitating the placement and forming of the next layer.

[0025] (3) Repeat the above steps until all layers are completed to further improve the interlayer bonding strength.

[0026] (4) Select a silicon-based heat transfer oil with a high thermal conductivity. Drive the flow rate of the oil through a pump, heat the upper surface of the die to the melting temperature of the prepreg, apply a pressure of 100 - 500 N with the placement head to promote the diffusion of molecular chains between resin layers. After the placement is completed, switch to the gradient cooling mode, and control the oil temperature to decrease at a rate of 5 - 10 °C / min to suppress the residual stress and obtain the final finished part.

[0027] The gradient cooling stage adopts a two-stage cooling strategy: in the first stage, the temperature is decreased at a rate of 10 - 15 °C / min to 180 - 200 °C, and in the second stage, the temperature is decreased at a rate of 5 - 10 °C / min to below 140 °C.

[0028] The thermoplastic prepreg tow uses T800 grade carbon fiber / polyaryletherketone prepreg with a surface density of 210 ± 10 g / m 2 。

[0029] Technical effects of the present invention: The oil heating mold design method of the present invention heats the mold through a high thermal conductivity medium (such as silicone oil, heat-conducting oil), providing an innovative solution for the thermoplastic AFP process. Its core advantages are as follows: (1) The high heat capacity and convective heat transfer characteristics of the oil medium can significantly improve the overall heat transfer efficiency of the mold. Combined with the optimized design of the runner topology, uniform distribution of the surface temperature field of the complex curved surface mold can be achieved, improving the interlayer performance of the workpiece; (2) The closed-loop temperature control system can dynamically match the transient heat demand of the laying process (such as heating rate > 20°C / s, cooling rate controllable) by adjusting the oil temperature and flow rate in real time, synchronously optimizing the melting quality and crystallization behavior; (3) Compared with resistance heating, the oil circulation system reduces energy consumption by more than 30% through the recycling of heat energy, and there is no risk of local overheating, significantly improving the process stability and mold life. This technology provides a new process equipment foundation with temperature control accuracy, energy efficiency ratio, and engineering adaptability for the efficient and automated forming of thermoplastic composites. Description of the Drawings

[0030] Figure 1 Schematic diagram of the mold;

[0031] Figure 2 Schematic diagram of the pipeline design in the top view direction. Detailed Embodiments

[0032] The present invention will be further described below with reference to the drawings and embodiments:

[0033] As Figure 1 Figure 2 shown, an automatic laying device for thermoplastic composite parts based on an oil heating mold includes a forming mold for complex-shaped parts, a high thermal conductivity oil circulation heating system, an automatic laying actuator, and a temperature control module; a runner network matching the geometric features of the complex-shaped part is designed inside the forming mold for complex-shaped parts. The runners are distributed in a staggered manner along the normal direction of the mold surface, with a height difference of 3 - 5 mm between adjacent runners, and the runner spacing is adjusted according to the local curvature radius. A serpentine pipe with a diameter of 8 - 12 mm is arranged 8 - 12 mm below the forming mold, with a spacing of 80 - 120 mm, as the high-temperature heat-conducting silicone oil delivery pipe; the high thermal conductivity oil circulation heating system includes a high-temperature silicone oil storage tank, a centrifugal pump, and connecting pipes. The centrifugal pump drives the high-temperature silicone oil in the high-temperature silicone oil storage tank to flow through the runner network, combined with the gradient temperature control module, to achieve uniform surface temperature of the mold; the automatic laying actuator integrates a pressure roller and a tension control unit, with a laying speed of 20 - 260 mm / s, dynamically matching the curvature change path to ensure resin melting and sufficient diffusion between prepreg layers; the melt index of the polyaryletherketone resin ≥ 90 g / 10 min (test conditions: 380°C / 5 kg).

[0034] The temperature sensor in the temperature control module has an accuracy of ±1°C.

[0035] The surface temperature fluctuation of the mold is ≤ ±2°C.

[0036] The forming mold is made of nickel-based superalloy or Q235 steel, and a three-dimensional profile-following runner network is integrated inside it.

[0037] The runner spacing is adjusted according to the local curvature radius. When R ≤ 30 mm, it is encrypted to 80 - 100 mm; when R > 30 mm, it is extended to 100 - 120 mm to adapt to the heat flux density requirements of complex surfaces.

[0038] The pressure of the pressure roller is 100 - 500 N.

[0039] The pressure of the tension control unit is 2 - 5 N.

[0040] Through the runner-profile coupling design and dynamic thermal management, this device breaks through the bottlenecks of thermal gradient and response hysteresis in traditional heating processes, and realizes the high-precision automatic forming of complex components.

[0041] In the thermoplastic composite material, the resin is polyaryletherketone resin, and the fiber is high-performance carbon fiber. The melt index of the polyaryletherketone resin is ≥ 90 g / 10 min, and the areal density of the prepreg is 210 g / m 2 .

[0042] If the forming surface is large and complex, when laying the prepreg tow in the next area, the thermoplastic prepreg laid in the previous area may have cooled and solidified. This non-uniformity is likely to generate internal stress, affecting the performance of the final part. At the same time, during the laying process, the interlayer bonding of thermoplastic composite materials relies on hot melt bonding. During laying, it is necessary to ensure that each layer of material is fully melted and tightly bonded to the lower layer to avoid pores or delamination. Therefore, it is necessary to continuously heat the mold during the laying process to facilitate the forming preparation of complex curved parts;

[0043] A method for using an oil-heated mold in the automatic laying process of thermoplastic composite materials includes the following steps:

[0044] (1) Clean the mold surface. Pass a high thermal conductivity medium into the pipeline through a centrifugal pump at a flow rate of 1.5 L / min, and heat the mold surface to the melting temperature of the thermoplastic prepreg;

[0045] (2) Use an automatic laying actuator to lay the thermoplastic prepreg tow on the mold surface, and apply a pressure of 100 - 500 N with a pressure roller to ensure that the prepreg fits the mold surface, facilitating the laying and forming of the next layer;

[0046] (3) Repeat the above steps until all layers are completed to further improve the interlayer bonding strength;

[0047] (4) Select a silicon-based heat-conducting oil with a high heat conductivity. Drive the flow rate of the oil through a pump to heat the upper surface of the mold to the melting temperature of the prepreg. The laying head applies a pressure of 100 - 500 N to promote the diffusion of molecular chains between resin layers. After the laying is completed, switch to the gradient cooling mode and control the oil temperature to decrease at a rate of 5 - 10 °C / min to suppress residual stress and obtain the final finished part.

[0048] The gradient cooling stage adopts a two-stage temperature reduction strategy: in the first stage, the temperature is reduced at a rate of 10 - 15 °C / min to 180 - 200 °C, and in the second stage, the temperature is reduced at a rate of 5 - 10 °C / min to below 140 °C.

[0049] Cool the mold by adjusting the temperature and flow rate of the heat-conducting oil, enabling the polyaryletherketone resin to fully crystallize, reducing its internal stress, improving the dimensional stability of the part, reducing the risk of part deformation, and further enhancing the quality of the formed part.

[0050] The thermoplastic prepreg tow uses T800 grade carbon fiber / polyaryletherketone prepreg with a surface density of 210 ± 10 g / m 2 .

[0051] Example 1

[0052] (1) Use T800 grade carbon fiber / polyaryletherketone prepreg as the tow for automatic laying. Clean the surface of the mold. Use a pump to push the silicon-based heat-conducting oil to flow through the inside of the mold, control the flow rate at 1.5 L / min, and conduct a temperature test. When the mold temperature reaches 360 °C, start laying the prepreg tow.

[0053] (2) The remaining laying parameters in this process are as follows: the automatic laying speed is 20 - 260 mm / s, which is adjusted according to the curvature change of the mold, the laying pressure is 300 N, and the laying tension is 3 N.

[0054] (3) After the laying is completed, reduce the temperature of the heat-conducting oil and cool it to below 140 °C at a rate of 10 °C / min, and then cool it to room temperature by natural cooling to obtain the final part.

[0055] (4) Prepare laminate test specimens with the same laying process parameters and conduct short beam shear tests. The results are shown in the following table. The average interlayer strength of the specimens is 76.9 MPa.

[0056]

[0057]

Claims

1. An automatic placement device for thermoplastic composite parts based on an oil-heated mold, characterized in that, It includes a forming die for complex surface parts, a high - thermal - conductivity oil circulation heating system, an automatic placement actuator, and a temperature control module. A runner network matching the geometric features of the complex surface part is designed inside the forming die for complex surface parts. The runners are distributed in a staggered pattern along the normal direction of the die surface. The height difference between adjacent runners is 3 - 5 mm, and the runner spacing is adjusted according to the local curvature radius. At 8 - 12 mm below the forming die, serpentine pipes with a diameter of 8 - 12 mm are arranged at a spacing of 80 - 120 mm as high - temperature heat - conducting silicone oil conveying pipes. The high - thermal - conductivity oil circulation heating system includes a high - temperature silicone oil storage tank, a centrifugal pump, and connecting pipes. The centrifugal pump drives the high - temperature silicone oil in the high - temperature silicone oil storage tank to flow through the runner network. Combined with the gradient temperature control module, the temperature uniformity of the die surface is achieved. The automatic placement actuator integrates a pressure roller and a tension control unit, with a placement speed of 20 - 260 mm / s, dynamically matching the curvature change path to ensure that the resin can fully diffuse between the prepreg layers after melting.

2. The automatic placement device for thermoplastic composite parts based on an oil-heated mold according to claim 1, characterized in that The temperature sensor in the temperature control module has an accuracy of ±1℃.

3. The automatic placement device for thermoplastic composite parts based on an oil-heated mold according to claim 1, wherein, The temperature fluctuation of the die surface is ≤±2℃.

4. The automatic placement device for thermoplastic composite parts based on an oil-heated mold according to claim 1, wherein, The forming die is made of nickel - based superalloy or Q235 steel, and a three - dimensional profiling runner network is integrated inside it.

5. The automatic laying device for thermoplastic composite parts based on an oil-heated mold according to claim 1, wherein, The runner spacing is adjusted according to the local curvature radius. When R≤30 mm, it is encrypted to 80 - 100 mm, and when R>30 mm, it is extended to 100 - 120 mm.

6. The automatic laying device for thermoplastic composite parts based on an oil-heated mold according to claim 1, characterized in that, The pressure of the pressure roller is 100 - 500 N.

7. The automatic laying device for thermoplastic composite parts based on an oil-heated mold according to claim 1, characterized in that The pressure of the tension control unit is 2 - 5 N.

8. The automatic placement device for thermoplastic composite parts based on an oil-heated mold according to claim 1, wherein, The resin in the thermoplastic composite material is a polyaryletherketone resin, the fiber is a high-performance carbon fiber, the melt index of the polyaryletherketone resin is ≥90 g / 10 min, and the areal density of the prepreg is 210 g / m 2 .

9. The usage method of an oil heating mold applied in the automatic placement process of thermoplastic composite materials according to any one of claims 1-8, characterized in that, It includes the following steps: (1) Clean the die surface. Pass a high - thermal - conductivity medium into the pipes through a centrifugal pump at a flow rate of 1.5 L / min, and heat the die surface to the melting temperature of the thermoplastic prepreg. (2) Use the automatic placement actuator to lay the thermoplastic prepreg tow on the die surface, and apply a pressure of 100 - 500 N with the pressure roller to ensure that the prepreg fits the die surface, facilitating the placement and forming of the next layer. (3) Repeat the above steps until all layers are completed to further improve the inter - layer bonding strength. (4) Select a silicon - based heat - conducting oil with a high heat - conductivity rate. Drive the oil flow rate through a pump to heat the upper surface of the die to the melting temperature of the prepreg. The placement head applies a pressure of 100 - 500 N to promote the diffusion of resin inter - layer molecular chains. After the placement is completed, switch to the gradient cooling mode, control the oil temperature to decrease at a rate of 5 - 10℃ / min to suppress the residual stress and obtain the final finished part. The gradient cooling stage adopts a two - stage cooling strategy: in the first stage, the temperature is decreased at a rate of 10 - 15℃ / min to 180 - 200℃, and in the second stage, the temperature is decreased at a rate of 5 - 10℃ / min to below 140℃.

10. The usage method of an oil heating mold applied in the automatic placement process of thermoplastic composite materials according to claim 9, characterized in that, The thermoplastic prepreg tow uses T800 grade carbon fiber / polyaryletherketone prepreg with a areal density of 210±10 g / m 2 .

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