Lightweight automobile ornament and processing and forming method thereof

Abstract

The invention belongs to the technical field of automobile ornament machining, and particularly relates to a light-weight automobile ornament and a machining forming method thereof.The technology comprises the steps that a multi-layer heterogeneous gradient reinforced framework structure is laid in an HP-RTM mold cavity, and the multi-layer heterogeneous gradient reinforced framework structure is fixed through vacuum adsorption and degradable fiber positioning pins; the preparation method comprises the following steps: mixing an epsilon-caprolactam monomer, a C10 initiator, a C20P catalyst, organic modified nano montmorillonite and a gamma-aminopropyltriethoxysilane coupling agent according to a mass ratio of 85: 6: 4: 3: 2, and carrying out ultrasonic dispersion to form a nano functional resin system; the mold is preheated to 145-155 DEG C, HP-RTM equipment is started to execute gradient pressure step-by-step injection, heat preservation and pressure maintaining are conducted for 4-6 min after infiltration, and anionic ring opening polymerization is completed; and the mold is opened, a formed part is taken out, then double-gradient curing is carried out, and finally the light-weight automobile ornament is obtained after laser finishing. Through collaborative innovation of ultrasonic-assisted step-by-step injection molding and double-gradient post-curing, the problems of insufficient infiltration, weak interface bonding and large internal stress of high fiber content are solved.

Description

Technical Field

[0001] This invention belongs to the field of automotive trim processing technology, specifically relating to a lightweight automotive trim part and its processing and forming method, which is applicable to load-bearing components of high-end automotive interior and exterior trim, and is especially suitable for new energy vehicle scenarios with stringent requirements for strength, lightweighting and dimensional accuracy. Background Technology

[0002] The demand for lightweight and high-strength synergy in automotive trim components has entered a refined stage of "gram-level weight reduction and megapascal-level strength enhancement." Existing composite molding technologies face three core challenges: 1. The problem of resin impregnation for high fiber content reinforced skeleton: Although traditional high pressure RTM can improve impregnation efficiency, the uneven fiber packing density of single fiber fabrics can easily lead to "dry fiber" defects in the core layer, making it difficult to reduce the porosity to below 0.3%. 2. The interfacial bonding between the in-situ polymerized resin and the fiber is weak. There is a mismatch between the polarity of the pure ε-caprolactam polymerized resin and the inertness of the carbon fiber surface, making it difficult to improve the interlaminar shear strength. 3. The accumulation of internal stress during the polymerization reaction and molding process, and the in-situ polymerization caused by temperature are prone to uneven reaction. Combined with the difference in the thermal expansion coefficients of resin and fiber, the dimensional accuracy error of the ornament exceeds ±0.1mm, and the risk of warping and deformation is high.

[0003] In view of this, the present invention proposes a lightweight automotive trim part and its processing and forming method. Summary of the Invention

[0004] To address the aforementioned shortcomings in existing technologies, this invention provides a lightweight automotive trim component and its processing and molding method. Through a collaborative innovation across the entire chain of "multi-layer heterogeneous gradient reinforced skeleton, nano-functionalized in-situ polymerized resin, ultrasonic-assisted stepwise injection molding, and dual-gradient post-curing," it solves the core pain points of insufficient wetting of high fiber content, weak interfacial bonding, high internal stress, and high cost, thereby achieving a leapfrog improvement in the performance of the trim component.

[0005] The specific technical solution includes the following steps: S1: The multi-layer heterogeneous gradient reinforced skeleton structure is laid in the HP-RTM mold cavity and fixed by vacuum adsorption and biodegradable fiber positioning pins. S2: A nanofunctionalized resin system is formed by ultrasonic dispersion of a mixture of ε-caprolactam monomer, C10 initiator, C20P catalyst, organic modified nano-montmorillonite, and γ-aminopropyltriethoxysilane coupling agent in a mass ratio of 85:6:4:3:2. S3: Preheat the mold to 145-155℃, start the HP-RTM equipment to perform gradient pressure stepwise injection, and after impregnation, keep the temperature and pressure for 4-6 minutes to complete the anionic ring-opening polymerization. S4: The molded part is removed from the mold, then dual-gradient curing is performed, and finally laser finishing is performed to obtain lightweight automotive trim parts.

[0006] The multilayer heterogeneous gradient reinforced skeleton in step S1 includes a surface fabric fiber, an intermediate glass fiber / carbon fiber hybrid layer, and a bottom fabric fiber, wherein the volume fraction of the surface fabric fiber is 45%-50%, the volume fraction of the intermediate glass fiber / carbon fiber hybrid layer is 40%-42%, and the volume fraction of the bottom fabric fiber is 43%-45%.

[0007] Secondly, in step S2, the mixed materials need to be ultrasonically dispersed at 125-135℃ for 12-18 minutes to form a low-viscosity, moisture-content ≤0.08wt% nanofunctionalized resin system.

[0008] Furthermore, the gradient pressure stepwise injection described in step S3 is divided into three stages; The first stage involves injecting resin into the surface fabric at a pressure of 30-40 bar for 20-25 seconds. The second stage involves increasing the pressure to 80-100 bar and filling the intermediate blended layer and bottom fabric, with an impregnation time of 30-35 seconds. The third stage involves maintaining a pressure of 100-120 bar; ultrasonic vibration is applied synchronously throughout the injection process, with a frequency of 25-30 kHz and a power of 60-80 W.

[0009] The mold cavity is equipped with an adaptive flow channel, the width of which varies with the fiber volume fraction gradient, with the surface channel width being 2mm, the middle channel width being 3mm, and the bottom channel width being 2.5mm.

[0010] Preferably, the dual-gradient curing in step S4 is divided into two stages; wherein, in the first stage, 20kHz ultrasound is applied at 105-115℃ and held for 70min; and in the second stage, 25kHz ultrasound is applied at 135-145℃ and cured for 45-55min, with a holding pressure of 0.15-0.25MPa applied throughout the curing process.

[0011] In step S2, the γ-aminopropyltriethoxysilane coupling agent generates hydroxyl groups through hydrolysis, which then form chemical bonds with the hydroxyl groups on the surface of nano-montmorillonite and fibers.

[0012] Secondly, the inner wall of the adaptive flow channel in step S3 is provided with an elastic seal. The channel width is dynamically adjusted according to the pressure during resin injection to ensure that the resin flows along the preset path and avoid fiber displacement.

[0013] Meanwhile, in step S3, the ultrasonic vibration direction is perpendicular to the resin flow direction, and the ultrasonic power is dynamically adjusted according to the injection stage, with 60W in the first stage, 70W in the second stage, and 80W in the third stage.

[0014] Furthermore, the processing method of the present invention can be used to manufacture lightweight load-bearing interior and exterior automotive trim parts, such as automotive door sill beam trim panels, seat rail trim covers, and luggage rack bases.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention utilizes the synergistic effect of nanofunctionalized resin and multilayer heterogeneous gradient skeleton to improve the tensile strength, interlaminar shear strength, impact energy absorption, and heat distortion temperature of the trim, thereby meeting the stringent requirements of high-end automotive load-bearing trim. 2. The present invention achieves lightweight and low-defect synergy: the high fiber content (40%-50%) and the high specific strength of the nano-modified composite material reduce the density of the ornament; the combination of ultrasonic-assisted stepwise injection and adaptive flow channel reduces the porosity of the ornament to below 0.15%, completely solving the "dry fiber" defect; 3. The present invention significantly improves dimensional accuracy and reliability: the internal stress release rate is improved through the dual-gradient ultrasonic curing process, the dimensional accuracy error of the ornament is ≤ ±0.08mm, and the warping deformation is ≤0.03mm / m; through interfacial chemical bonding and multi-layer heterogeneous structure design, the resistance of the ornament to damp heat aging is improved, there is no risk of delamination or cracking during long-term use, and the service life is greatly extended. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the molding process of an embodiment of a lightweight automotive trim part and its processing method according to the present invention. Detailed Implementation

[0017] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0018] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0019] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the accompanying drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0020] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] This invention provides a lightweight automotive trim part and its processing and molding method. Through the collaborative innovation of the entire chain of "multi-layer heterogeneous gradient reinforced skeleton, nano-functionalized in-situ polymerized resin, ultrasonic-assisted stepwise injection molding, and dual-gradient post-curing", it solves the core pain points of insufficient wetting of high fiber content, weak interface bonding, high internal stress and high cost, and achieves a leapfrog improvement in the performance of the trim part.

[0022] The specific molding steps are as follows: S1: Multi-layer heterogeneous gradient reinforced skeleton prefabrication innovative design "surface layer - middle layer - bottom layer" three-layer heterogeneous gradient reinforced structure, precisely matching the stress requirements of different areas of the ornament: Surface layer: 30k tow carbon fiber fabric with a surface density of 320-330g / m², the fibers are oriented along the main stress direction of the ornament, and the fiber volume fraction is 45%-50%, to ensure the surface layer's impact resistance and abrasion resistance. Intermediate layer: A 6:4 plain weave carbon fiber / glass fiber hybrid layer is used, with a surface density of 280-290 g / m² and a fiber volume fraction of 40%-42%. The cost is balanced by the low cost characteristics of glass fiber, while the interfacial interlocking effect of the hybrid structure is used to improve the interlayer bonding stability. Bottom layer: 50k tow multiaxial carbon fiber fabric with a surface density of 300-310g / m², fiber orientation of ±45° / 0° / 90°, and fiber volume fraction of 43%-45%, ensuring the bottom layer's resistance to deformation and load-bearing capacity.

[0023] The three layers of fabric are laid sequentially into the HP-RTM mold cavity, using a dual fixation method of "vacuum adsorption and biodegradable positioning pins": the vacuum system is activated to evacuate the cavity to a vacuum level of ≥950 mbar, compacting the fabric through negative pressure; polylactic acid / starch composite positioning pins are placed along the edges of the skeleton and at key stress points, with a spacing of 30-40 mm between the pins to prevent fiber displacement during injection. The positioning pins can be subsequently removed via hot water degradation, leaving no residue.

[0024] S2: Preparation of a nanofunctionalized in-situ polymerized resin system using ε-caprolactam as the matrix monomer. Breaking away from traditional single-polymerization systems, this system introduces a dual-functional component combining "nano-reinforcement + interface modification": a mixture of ε-caprolactam monomer, C10 initiator, C20P catalyst, organically modified nano-montmorillonite, and γ-aminopropyltriethoxysilane coupling agent in a mass ratio of 85:6:4:3:2. The mixture is placed in a temperature-controlled reactor and heated to 125-135℃, while simultaneously subjected to ultrasonic dispersion treatment at 28-35kHz and 80-100W for 12-18 minutes. Ultrasonic vibration promotes uniform dispersion of nano-montmorillonite, preventing agglomeration, and accelerates the hydrolysis of the coupling agent to generate hydroxyl groups. The final result is a low-viscosity (2-3 mPa·s) nanofunctionalized resin system with a moisture content ≤0.08wt%. Nano-montmorillonite enhances the resin modulus and heat resistance, and the hydroxyl groups of the coupling agent form chemical bonds with the hydroxyl groups on the fiber surface and the nano-montmorillonite, fundamentally solving the problem of weak interfacial bonding.

[0025] To further enhance thermal conductivity and impact resistance, an additional 1-2 wt% of carbon nanotubes can be added to create a synergistic reinforcing effect with nano-montmorillonite.

[0026] S3: Ultrasonic-Assisted Stepwise Injection Molding – In-situ Polymerization. Addressing the fiber volume fraction differences in a three-layer gradient reinforced skeleton, an innovative integrated process of "stepwise injection – gradient pressure + ultrasonic assistance" is designed, coupled with an adaptive flow channel mold to achieve precise impregnation. Mold pretreatment: Preheat the HP-RTM mold to 145-155℃. The mold cavity is equipped with an adaptive flow channel. The width of the channel changes with the fiber volume fraction gradient (2mm for the surface layer → 3mm for the middle layer → 2.5mm for the bottom layer). The elastic seal on the inner wall of the channel can dynamically adjust the width of the channel according to the injection pressure to ensure that the resin flows along the preset path and avoid fiber displacement. Stepwise injection: First stage: Inject resin at a low pressure of 30-40 bar, prioritizing the wetting of the surface area with high fiber content, with a wetting time of 20-25 seconds, to avoid fiber collapse caused by high pressure impact. Second stage: Increase the pressure to 80-100 bar, quickly fill the middle blended layer and the bottom multi-axial fabric area, with an impregnation time of 30-35 seconds, and use high pressure to overcome the flow resistance caused by the accumulation of core fibers. Third stage: Hold pressure at 100-120 bar to ensure that the resin fully penetrates into the fiber gaps; Ultrasonic-assisted initiation: Ultrasonic vibration is applied synchronously throughout the injection process (direction perpendicular to the resin flow direction), and the power is dynamically adjusted according to the stage (60W→70W→80W): Ultrasonic vibration can reduce resin viscosity and promote molecular diffusion. At the same time, it acts as an "auxiliary initiation source" for in-situ polymerization, enabling the polymerization reaction to start synchronously from the fiber surface and the inside of the resin, avoiding the accumulation of internal stress caused by uneven reaction. In-situ polymerization: After holding at temperature and pressure for 4-6 minutes, ε-caprolactam completes anionic ring-opening polymerization in situ within the reinforcing skeleton, forming a nano-montmorillonite modified PA6 / carbon fiber (PA6 / CF / MMT) composite structure.

[0027] S4: Ultrasonic-assisted gradient post-curing and precision finishing innovatively adopts a dual-gradient curing process of "ultrasonic + temperature" combined with femtosecond laser finishing to maximize the release of internal stress and improve dimensional accuracy. Positioning pin removal: Open the mold and take out the molded part, immerse it in hot water at 80-90℃ for 5-8 minutes, the degradable positioning pin will be completely degraded (degradation rate ≥95%), and there will be no residue after rinsing; Dual gradient curing: The molded part is placed in an ultrasonic-assisted curing oven to perform a two-stage process: First stage: 105-115℃ + 20kHz ultrasonic heat preservation for 70min to slowly promote the polymerization reaction to end and initially release the interfacial stress. Second stage: Heat to 135-145℃ and ultrasonically cure at 25kHz for 45-55 minutes to increase the crosslinking density of the resin, while ultrasonic vibration accelerates the release of interlayer stress. A holding pressure of 0.15-0.25 MPa is applied throughout the curing process to prevent deformation caused by polymerization shrinkage; Femtosecond laser finishing: Using a femtosecond laser device with a power of 800-1000W and a speed of 30-40mm / s, and a spot diameter of 50-80μm, the edges and surfaces of the ornaments are finished to remove burrs, flash, and residual resin. The final edge perpendicularity error of the ornament is ≤0.05mm, the surface roughness Ra is ≤0.3μm, and the dimensional accuracy error is ≤±0.08mm.

[0028] Example 1: A lightweight automotive trim part and its processing method include the following steps: S1: Multi-layer heterogeneous gradient reinforced skeleton prefabrication: The surface layer uses 30k unidirectional carbon fiber fabric (area density 325g / m², fiber volume fraction 48%), the middle layer is a 6:4 plain weave carbon fiber / glass fiber hybrid layer (area density 285g / m², fiber volume fraction 41%), and the bottom layer is 50k multiaxial carbon fiber fabric (area density 305g / m², fiber volume fraction 44%). After the three layers of fabric are laid, the vacuum is drawn to 960mbar, and polylactic acid / starch positioning pins are arranged (spacing 35mm). S2: Preparation of nanofunctionalized in-situ polymerized resin system: ε-caprolactam, C10 initiator, C20P catalyst, organically modified nano-montmorillonite (30nm, interlayer spacing 35nm), and γ-aminopropyltriethoxysilane were mixed at a mass ratio of 85:6:4:3:2 and ultrasonically dispersed at 130℃, 30kHz, and 90W for 15min. The resin viscosity was 2.5mPa·s, and the moisture content was 0.06wt%. S3: Ultrasonic-assisted stepwise injection molding – in-situ polymerization: Mold preheated to 150℃, adaptive flow channel with a surface width of 2mm, a middle width of 3mm, and a bottom width of 2.5mm; first stage: 35 bar injection for 22s, second stage: 90 bar injection for 32s, third stage: 110 bar holding pressure; ultrasonic power: 60W→70W→80W, frequency: 28kHz; heat and pressure holding for 5min; S4: Ultrasonic-assisted gradient post-curing and precision finishing: Immerse in 85℃ hot water for 6 min to remove positioning pins; ultrasonic heat preservation at 110℃ + 20kHz for 70 min, ultrasonic curing at 140℃ + 25kHz for 50 min, pressure holding 0.2MPa; femtosecond laser finishing (power 900W, speed 35mm / s, spot size 70μm).

[0029] Final performance of the decorative component: density 0.82 g / cm³, tensile strength 565 MPa, interlaminar shear strength 49.2 MPa, porosity 0.12%, dimensional accuracy error ±0.07 mm, surface roughness Ra=0.28 μm, and strength retention rate 92% after 1000 h of humid heat aging.

[0030] Example 2: Referring to Example 1, only the following parameters were adjusted: S2: 1.5wt% carbon nanotubes (diameter 15nm, length 8μm) were added, and the ultrasonic dispersion time was extended to 18min; S3: the mold was preheated to 155℃, and the pressure in the third stage was 120bar; S4: the femtosecond laser finishing power was 1000W and the speed was 40mm / s.

[0031] Final trim performance: density 0.83 g / cm³, tensile strength 582 MPa, interlaminar shear strength 51.5 MPa, thermal conductivity increased to 1.8 W / (m・K), and impact energy absorption increased by 40%.

[0032] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for processing and molding lightweight automotive trim parts, characterized in that, Includes the following steps: S1: The multi-layer heterogeneous gradient reinforced skeleton structure is laid in the HP-RTM mold cavity and fixed by vacuum adsorption and biodegradable fiber positioning pins. S2: A nanofunctionalized resin system is formed by ultrasonic dispersion of a mixture of ε-caprolactam monomer, C10 initiator, C20P catalyst, organic modified nano-montmorillonite, and γ-aminopropyltriethoxysilane coupling agent in a mass ratio of 85:6:4:3:

2. S3: Preheat the mold to 145-155℃, start the HP-RTM equipment to perform gradient pressure stepwise injection, and after impregnation, keep the temperature and pressure for 4-6 minutes to complete the anionic ring-opening polymerization. S4: The molded part is removed from the mold, then dual-gradient curing is performed, and finally laser finishing is performed to obtain lightweight automotive trim parts.

2. The processing and forming method for a lightweight automotive trim part according to claim 1, characterized in that: The multilayer heterogeneous gradient reinforced skeleton in step S1 includes a surface fabric fiber, an intermediate glass fiber / carbon fiber hybrid layer, and a bottom fabric fiber, wherein the volume fraction of the surface fabric fiber is 45%-50%, the volume fraction of the intermediate glass fiber / carbon fiber hybrid layer is 40%-42%, and the volume fraction of the bottom fabric fiber is 43%-45%.

3. The processing and forming method for a lightweight automotive trim part according to claim 1, characterized in that: In step S2, the mixed materials need to be ultrasonically dispersed at 125-135℃ for 12-18 minutes to form a low-viscosity, moisture-content ≤0.08wt% nanofunctionalized resin system.

4. The method for processing and forming a lightweight automotive trim part according to claim 1, characterized in that: The gradient pressure stepwise injection described in step S3 is divided into three stages; The first stage involves injecting resin into the surface fabric at a pressure of 30-40 bar for 20-25 seconds. The second stage involves increasing the pressure to 80-100 bar and filling the intermediate blended layer and bottom fabric, with an impregnation time of 30-35 seconds. The third stage involves maintaining a pressure of 100-120 bar; ultrasonic vibration is applied synchronously throughout the injection process, with a frequency of 25-30 kHz and a power of 60-80 W.

5. The method for processing and forming a lightweight automotive trim part according to claim 1, characterized in that: The mold cavity is equipped with an adaptive flow channel, the width of which varies with the fiber volume fraction gradient, wherein the surface channel width is 2mm, the middle channel width is 3mm, and the bottom channel width is 2.5mm.

6. The method for processing and forming a lightweight automotive trim part according to claim 1, characterized in that: The dual-gradient curing described in step S4 is divided into two stages; in the first stage, 20kHz ultrasound is applied at 105-115℃ and held for 70min; in the second stage, 25kHz ultrasound is applied at 135-145℃ and cured for 45-55min, with a holding pressure of 0.15-0.25MPa applied throughout the curing process.

7. The method for processing and forming a lightweight automotive trim part according to claim 1, characterized in that: The γ-aminopropyltriethoxysilane coupling agent described in step S2 generates hydroxyl groups through hydrolysis, which then form chemical bonds with the hydroxyl groups on the surface of nano-montmorillonite and fibers.

8. The method for processing and forming a lightweight automotive trim part according to claim 5, characterized in that: The adaptive flow channel described in step S3 is equipped with an elastic seal on its inner wall. The channel width is dynamically adjusted according to pressure changes during resin injection to ensure that the resin flows along a preset path and prevent fiber displacement.

9. The method for processing and forming a lightweight automotive trim part according to claim 1, characterized in that: In step S3, the ultrasonic vibration direction is perpendicular to the resin flow direction, and the ultrasonic power is dynamically adjusted according to the injection stage, with 60W in the first stage, 70W in the second stage, and 80W in the third stage.

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