CN121515519A - A lightweight automotive trim part and its processing and forming method - Google Patents

Abstract

The invention belongs to the technical field of automobile ornament processing, and particularly relates to a lightweight automobile ornament and a processing and molding method thereof, wherein the process comprises the steps of paving a multi-layer heterogeneous gradient reinforced skeleton structure in an HP-RTM mold cavity, and fixing the multi-layer heterogeneous gradient reinforced skeleton structure through vacuum adsorption and degradable fiber locating pins; the method comprises the steps of forming a nano functional resin system by ultrasonic dispersion of a mixed material epsilon-caprolactam monomer, a C10 initiator, a C20P catalyst, organic modified nano montmorillonite and a gamma-aminopropyl triethoxy silane coupling agent according to a mass ratio of 85:6:4:3:2, preheating a die to 145-155 ℃, starting HP-RTM equipment to execute gradient pressure step injection, preserving heat and pressure for 4-6 min after infiltration, completing anion ring-opening polymerization, opening the die, taking out a formed part, then executing double gradient curing, and finally obtaining the lightweight automobile ornament after laser finishing. Through the cooperative innovation of ultrasonic-assisted step injection molding and dual-gradient post-curing, the problems of insufficient infiltration of high fiber content, weak interface bonding and large internal stress are solved.

Description

Light-weight automobile ornament and processing and forming method thereof

Technical Field

The invention belongs to the technical field of automobile ornament processing, and particularly relates to a light-weight automobile ornament and a processing and forming method thereof, which are suitable for high-end automobile interior and exterior decorative bearing parts, in particular to a new energy automobile scene with strict requirements on strength, light weight and dimensional accuracy.

Background

The light weight and high strength cooperative demand of the automobile ornament enters the refinement stage of gram weight reduction and megapascal strength enhancement, and the existing composite molding technology has three major core problems:

1. the resin infiltration problem of the high-fiber-content reinforced skeleton is solved, the infiltration efficiency can be improved by the traditional high-pressure RTM, but the fiber stacking density of a single fiber fabric is uneven, so that the defect of dry fiber of a core layer is easily caused, and the porosity is difficult to be reduced to below 0.3%;

2. the interface combination of the in-situ polymerized resin and the fiber is weak, the polarity of the pure epsilon-caprolactam polymerized resin has the contradiction with the inertia of the surface of the carbon fiber, and the interlaminar shear strength is difficult to improve;

3. internal stress in the polymerization reaction and the forming process is accumulated, in-situ polymerization initiated by temperature is easy to generate uneven reaction, and the difference of thermal expansion coefficients of the superimposed resin and the fiber leads to the dimensional accuracy error of the ornament exceeding +/-0.1 mm and high buckling deformation risk.

In view of the above, the invention provides a lightweight automotive trim part and a processing and forming method thereof.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a lightweight automobile ornament and a processing and forming method thereof, and the full-chain collaborative innovation of multilayer heterogeneous gradient reinforced framework, nano functional in-situ polymer resin, ultrasonic assisted step injection molding and dual gradient post curing is adopted, so that core pain points with insufficient high fiber content infiltration, weak interface combination, large internal stress and high cost are solved, and the spanning type improvement of the ornament performance is realized.

The specific technical scheme comprises the following steps:

S1, paving a multi-layer heterogeneous gradient reinforced skeleton structure in an HP-RTM mold cavity, and fixing the multi-layer heterogeneous gradient reinforced skeleton structure through vacuum adsorption and degradable fiber locating pins;

s2, performing ultrasonic dispersion on epsilon-caprolactam monomer, a C10 initiator, a C20P catalyst, organically modified nano montmorillonite and a gamma-aminopropyl triethoxysilane coupling agent which are mixed according to a mass ratio of 85:6:4:3:2 to form a nano functional resin system;

s3, preheating a die to 145-155 ℃, starting HP-RTM equipment to execute gradient pressure step injection, and preserving heat and pressure for 4-6 min after infiltration to complete anion ring-opening polymerization;

and S4, opening the die, taking out the formed part, then performing dual-gradient curing, and finally performing laser finishing to obtain the lightweight automobile ornament.

The multilayer heterogeneous gradient reinforced skeleton in the step S1 comprises surface fabric fibers, a middle glass fiber/carbon fiber mixed woven layer and bottom fabric fibers, wherein the volume fraction of the surface fabric fibers is 45% -50%, the volume fraction of the middle glass fiber/carbon fiber mixed woven layer is 40% -42%, and the volume fraction of the bottom fabric fibers is 43% -45%.

Secondly, the mixed material in the step S2 needs to be dispersed for 12-18 min under the temperature of 125-135 ℃ to form a nano functionalized resin system with low viscosity and the moisture content of less than or equal to 0.08 wt%.

Further, in step S3, the gradient pressure step injection is divided into three stages;

The first stage, injecting resin at 30-40bar pressure to infiltrate the surface fabric for 20-25 s;

step two, boosting to 80-100bar to fill the middle mixed knitting layer and the bottom fabric, and soaking for 30-35 s;

the third stage of pressure maintaining is 100-120bar, ultrasonic vibration is synchronously applied in the whole injection process, the frequency is 25-30kHz, and the power is 60-80W.

Wherein, the die cavity is provided with a self-adaptive diversion trench, the trench width changes with the gradient of the fiber volume fraction, the trench width of the surface layer is 2mm, the trench width of the middle layer is 3mm, and the trench width of the bottom layer is 2.5mm.

Preferably, the dual-gradient curing in the step S4 is divided into two stages, wherein the first stage is to apply 20kHz ultrasonic waves at 105-115 ℃ and keep the temperature for 70min, the second stage is to apply 25kHz ultrasonic waves at 135-145 ℃ and cure for 45-55 min, and the whole curing process is to apply pressure maintaining pressure of 0.15-0.25 MPa.

Wherein, in the step S2, the gamma-aminopropyl triethoxy silane coupling agent generates hydroxyl through hydrolysis, and forms chemical bonding with nano montmorillonite and hydroxyl on the surface of fiber.

And secondly, in the step S3, an elastic sealing piece is arranged on the inner wall of the self-adaptive diversion trench, and the trench width is dynamically adjusted along with the pressure change during resin injection, so that the resin is ensured to flow along a preset path, and the fiber displacement is avoided.

Meanwhile, in the step S3, the ultrasonic vibration direction is perpendicular to the resin flowing direction, the ultrasonic power is dynamically adjusted along with the injection stage, wherein the first stage is 60W, the second stage is 70W, and the third stage is 80W.

Furthermore, the processing method of the invention is used for manufacturing the internal and external bearing light-weight decorative parts of the automobile, such as the automobile threshold beam decorative plate, the seat slide rail decorative cover, the luggage rack base and the like.

Compared with the prior art, the invention has the following beneficial effects:

1. according to the invention, through the synergistic effect of the nano functional resin and the multi-layer heterogeneous gradient skeleton, the tensile strength, interlayer shearing strength and impact absorption energy of the ornament are improved, the thermal deformation temperature is greatly improved, and the severe requirements of the high-end automobile bearing ornament are met;

2. The invention has the advantages that the light weight and the low defect cooperate to reach the standard, namely, the high specific strength characteristic of the high fiber content (40% -50%) and the nano modified composite material, the density of the ornament is reduced, the ultrasonic auxiliary step injection is matched with the self-adaptive diversion trench, the porosity of the ornament is reduced to below 0.15%, and the defect of dry fiber is thoroughly solved;

3. the invention has the advantages of improving the internal stress release rate through a double-gradient ultrasonic curing process, improving the moisture and heat aging resistance of the ornament through interface chemical bonding and multilayer heterostructure design, avoiding layering and cracking risks after long-term use, and greatly improving the service life, along with improving the dimensional accuracy error of the ornament by less than or equal to +/-0.08 mm and the warp deformation amount of less than or equal to 0.03 mm/m.

Drawings

Fig. 1 is a flowchart of a molding process of an embodiment of a lightweight automotive trim part and a method for molding the same according to the present invention.

Detailed Description

The invention is further described in connection with the following detailed description in order to make the technical means, the creation characteristics, the achievement of the purpose and the effect of the invention easy to understand.

In which the drawings are for illustrative purposes only and are not intended to be construed as limiting the invention, and in which certain elements of the drawings may be omitted, enlarged or reduced in order to better illustrate embodiments of the invention, and not to represent actual product dimensions, it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

In the description of the present invention, it should be understood that, if the terms "upper", "lower", "left", "right", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, it is merely for convenience in describing the present invention and simplifying the description, and not to indicate or imply that the device or element referred to must have a specific orientation, be configured and operated in a specific orientation, so that the terms describing the positional relationships in the drawings are merely for exemplary illustration, and are not to be construed as limitations of the present invention, and that the specific meanings of the terms described above may be understood by those of ordinary skill in the art according to specific circumstances.

In the description of the present invention, unless explicitly stated or limited otherwise, the term "coupled" or the like should be interpreted broadly, as referring to a connection between two components, for example, a fixed connection, a removable connection, or a combination, a mechanical connection, an electrical connection, a direct connection, an indirect connection via an intermediary, a communication between two components, or an interaction between two components. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

The invention provides a lightweight automobile ornament and a processing and molding method thereof, which solve the core pain points of insufficient infiltration, weak interface combination, large internal stress and high cost of high fiber content and realize the spanning type improvement of ornament performance through full-chain collaborative innovation of multi-layer heterogeneous gradient reinforced skeleton, nano functional in-situ polymer resin, ultrasonic assisted step injection molding and dual gradient post curing.

The specific forming steps are as follows:

s1, prefabricating and innovative design of a three-layer heterogeneous gradient reinforcement structure of a surface layer-middle-bottom layer by a multi-layer heterogeneous gradient reinforcement framework, and accurately matching stress requirements of different areas of a decoration piece:

the surface layer is made of 30k tow carbon fiber fabric, the surface density is 320-330 g/m <2 >, the fiber is oriented along the main stress direction of the ornament, and the fiber volume fraction is 45-50%, so that the impact resistance and the wear resistance of the surface layer are ensured;

the middle layer adopts a carbon fiber/glass fiber 6:4 plain weave mixed weaving layer, the surface density is 280-290 g/m < 2 >, the fiber volume fraction is 40-42%, the cost is balanced through the low-cost characteristic of the glass fiber, and the interface occlusion effect of the mixed weaving structure is utilized to improve the interlayer combination stability;

The bottom layer is made of 50k silk bundle multi-axial carbon fiber fabric, the surface density is 300-310 g/m <2 >, the fiber orientation is +/-45 degrees/0 degrees/90 degrees, the fiber volume fraction is 43-45%, and the deformation resistance and the bearing capacity of the bottom layer are ensured.

The three-layer fabric is laid in the HP-RTM mold cavity layer by layer in sequence, and double fixation of vacuum adsorption and degradable locating pins is adopted, namely a vacuum system is started to pump the vacuum degree of the cavity to be more than or equal to 950mbar, the fabric is compacted through negative pressure, locating pins made of polylactic acid/starch composite materials are arranged along the edge of the framework and stress key points, the locating distance is 30-40 mm, and fiber displacement in the injection process is avoided. The locating pin can be subsequently removed through hot water degradation, and no residual impurities exist.

S2, preparing a nano functionalized in-situ polymerization resin system, namely taking epsilon-caprolactam as a matrix monomer, breaking through a traditional single polymerization system, and introducing a nano enhanced and interface modified dual-function component, wherein epsilon-caprolactam monomer, a C10 initiator, a C20P catalyst, organically modified nano montmorillonite and a gamma-aminopropyl triethoxysilane coupling agent are mixed according to a mass ratio of 85:6:4:3:2. The mixed system is placed in a temperature-controlled reaction kettle, the temperature is raised to 125-135 ℃, and simultaneously, ultrasonic dispersion treatment of 28-35kHz and 80-100W is applied for 12-18 min, wherein ultrasonic vibration not only promotes the uniform dispersion of nano montmorillonite to avoid agglomeration, but also accelerates the hydrolysis of a coupling agent to generate hydroxyl. Finally, a nano functional resin system with low viscosity (2-3 mPa, s) and moisture content less than or equal to 0.08wt% is formed, namely, nano montmorillonite can improve the resin modulus and heat resistance, and the hydroxyl of the coupling agent forms chemical bonding with the hydroxyl of the fiber surface and the hydroxyl of the nano montmorillonite, so that the problem of weak interface bonding is solved from the root.

If the heat conduction and impact resistance are required to be further improved, 1-2wt% of carbon nano tube can be additionally added to form a synergistic enhancement effect with nano montmorillonite.

S3, aiming at the difference of fiber volume fractions of three-layer gradient reinforced frameworks, an integrated process of step injection, gradient pressure and ultrasonic assistance is innovatively designed, and the integrated process is matched with a self-adaptive diversion trench die to realize accurate infiltration:

Preheating an HP-RTM die to 145-155 ℃, arranging a self-adaptive diversion trench in a die cavity, wherein the trench width changes along with the gradient of the fiber volume fraction (2 mm on the surface layer, 3mm in the middle and 2.5mm on the bottom layer), and the trench width of an elastic sealing element on the inner wall of the trench can be dynamically adjusted along with the injection pressure so as to ensure the resin to flow along a preset path and avoid fiber displacement;

step injection:

Injecting resin at low pressure of 30-40bar, and preferentially infiltrating the high-fiber-content area of the surface layer for 20-25 s, so as to avoid fiber lodging caused by high-pressure impact;

Step two, boosting to 80-100bar, rapidly filling the multi-axial fabric areas of the middle mixed knitting layer and the bottom layer, soaking for 30-35 s, and breaking through the flow resistance caused by the accumulation of the core layer fibers by using high pressure;

the third stage, maintaining the pressure at 100-120bar to ensure that the resin fully permeates into the fiber gaps;

ultrasonic auxiliary initiation, namely, the ultrasonic vibration (the direction is perpendicular to the flowing direction of the resin) is synchronously applied in the whole injection process, and the power is dynamically adjusted (60W-70W-80W) along with the stage, wherein the ultrasonic vibration can reduce the viscosity of the resin and promote the diffusion of molecules, and meanwhile, the ultrasonic vibration is used as an auxiliary initiation source for in-situ polymerization, so that the polymerization reaction is synchronously started from the surface of the fiber and the inside of the resin, and the internal stress accumulation caused by uneven reaction is avoided;

In-situ polymerization, namely, heat preservation and pressure maintaining are carried out for 4-6 min, and anion ring-opening polymerization of epsilon-caprolactam is completed in situ in the reinforced framework, so that a nano montmorillonite modified PA 6/carbon fiber (PA 6/CF/MMT) composite structure is formed.

S4, ultrasonic auxiliary gradient post-curing and accurate finishing innovatively adopts an ultrasonic and temperature dual-gradient curing process, and is matched with femtosecond laser finishing, so that the internal stress is released to the maximum extent, and the dimensional accuracy is improved:

Removing the locating pin, namely opening the mould, taking out the formed part, soaking the formed part in 80-90 ℃ hot water for 5-8 min, and completely degrading the degradable locating pin (the degradation rate is more than or equal to 95 percent), wherein no residue exists after flushing;

and (3) double-gradient curing, namely feeding the molded part into an ultrasonic auxiliary curing oven, and executing a two-stage process:

the first stage, in which ultrasonic heat preservation is carried out for 70min at 105-115 ℃ and 20kHz, the ending of the polymerization reaction is slowly promoted, and the internal stress of an interface is primarily released;

the second stage, heating to 135-145 ℃ and ultrasonic curing at +25kHz for 45-55 min, improving the crosslinking density of the resin, and simultaneously accelerating the release of internal stress between layers by ultrasonic vibration;

the pressure maintaining pressure of 0.15-0.25MPa is applied in the whole curing process, so that the deformation caused by polymerization shrinkage is avoided;

And (3) performing femtosecond laser finishing, namely finishing the edge and the surface of the ornament by using a femtosecond laser device with the power of 800-1000W and the speed of 30-40 mm/s, wherein the spot diameter is 50-80 mu m, removing burrs, flash and residual resin, wherein the perpendicularity error of the edge of the ornament is less than or equal to 0.05mm, the surface roughness Ra is less than or equal to 0.3 mu m, and the dimensional accuracy error is less than or equal to +/-0.08 mm.

Embodiment one:

a light-weight automobile ornament and a processing and forming method thereof comprise the following steps:

the method comprises the steps of S1, prefabricating a multi-layer heterogeneous gradient reinforced skeleton, wherein a surface layer is made of 30k unidirectional carbon fiber fabrics (the surface density is 325g/m & lt 2 & gt and the fiber volume fraction is 48%), a middle layer is made of carbon fiber/glass fiber 6:4 plain weave mixed weaving layers (the surface density is 285g/m & lt 2 & gt and the fiber volume fraction is 41%), a bottom layer is made of 50k multi-axial carbon fiber fabrics (the surface density is 305g/m & lt 2 & gt and the fiber volume fraction is 44%), and after three layers of fabrics are paved, vacuum pumping is carried out to 960mbar, and polylactic acid/starch locating pins (the distance is 35 mm) are arranged;

S2, preparing a nano functional in-situ polymerization resin system, namely mixing epsilon-caprolactam, a C10 initiator, a C20P catalyst, organically modified nano montmorillonite (30 nm, layer spacing 35 nm) and gamma-aminopropyl triethoxysilane according to the mass ratio of 85:6:4:3:2, performing ultrasonic dispersion for 15min at 130 ℃ at 30kHz and 90W, wherein the resin viscosity is 2.5mPa, S and the water content is 0.06wt%;

S3, ultrasonic-assisted step injection-in-situ polymerization molding, namely preheating a mold to 150 ℃, enabling the surface layer of the self-adaptive diversion trench to be 2mm wide, enabling the middle of the self-adaptive diversion trench to be 3mm, enabling the bottom layer to be 2.5mm, enabling the first stage to be 35bar to be injected for 22S, the second stage to be 90bar to be injected for 32S, enabling the third stage to be 110bar to maintain pressure, enabling the ultrasonic power to be 60W, 70W, 80W, enabling the frequency to be 28kHz, and keeping the temperature and the pressure for 5min;

S4, ultrasonic auxiliary gradient post-curing and accurate finishing, namely removing the locating pin by soaking in hot water at 85 ℃ for 6min, insulating for 70min by ultrasonic at 110 ℃ and 20kHz, curing for 50min by ultrasonic at 140 ℃ and 25kHz, maintaining the pressure for 0.2MPa, and finishing by femtosecond laser (power 900W, speed 35mm/S and light spot 70 mu m).

The final ornament performance comprises density of 0.82g/cm < 3 >, tensile strength of 565MPa, interlaminar shear strength of 49.2MPa, porosity of 0.12%, dimensional accuracy error of +/-0.07 mm, surface roughness Ra=0.28 mu m and strength retention rate of 92% after 1000h of wet heat aging resistance.

Example two referring to example 1, only the following parameters were adjusted S2: 1.5wt% carbon nanotubes (diameter 15nm, length 8 μm) were added, the ultrasonic dispersion time was prolonged to 18min, S3: the mold was preheated to 155 ℃, the third stage was holding 120bar, S4: the femtosecond laser finishing power was 1000W, and the speed was 40mm/S.

The final ornament performance is that the density is 0.83g/cm < 3 >, the tensile strength is 582MPa, the interlayer shearing strength is 51.5MPa, the heat conductivity coefficient is improved to 1.8W/(m seed K), and the impact absorption energy is improved by 40%.

The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (9)

1. The processing and forming method of the light-weight automobile ornament is characterized by comprising the following steps of:

S1, paving a multi-layer heterogeneous gradient reinforced skeleton structure in an HP-RTM mold cavity, and fixing the multi-layer heterogeneous gradient reinforced skeleton structure through vacuum adsorption and degradable fiber locating pins;

s2, performing ultrasonic dispersion on epsilon-caprolactam monomer, a C10 initiator, a C20P catalyst, organically modified nano montmorillonite and a gamma-aminopropyl triethoxysilane coupling agent which are mixed according to a mass ratio of 85:6:4:3:2 to form a nano functional resin system;

s3, preheating a die to 145-155 ℃, starting HP-RTM equipment to execute gradient pressure step injection, and preserving heat and pressure for 4-6 min after infiltration to complete anion ring-opening polymerization;

and S4, opening the die, taking out the formed part, then performing dual-gradient curing, and finally performing laser finishing to obtain the lightweight automobile ornament.

2. The method for forming a lightweight automotive trim part according to claim 1, characterized in that:

The multilayer heterogeneous gradient reinforced skeleton in the step S1 comprises surface fabric fibers, a middle glass fiber/carbon fiber mixed woven layer and bottom fabric fibers, wherein the volume fraction of the surface fabric fibers is 45% -50%, the volume fraction of the middle glass fiber/carbon fiber mixed woven layer is 40% -42% and the volume fraction of the bottom fabric fibers is 43% -45%.

3. The method for forming a lightweight automotive trim part according to claim 1, characterized in that:

the mixed material in the step S2 needs to be dispersed for 12-18 min under the temperature of 125-135 ℃ to form a nano functional resin system with low viscosity and the moisture content of less than or equal to 0.08 wt%.

4. The method for forming a lightweight automotive trim part according to claim 1, characterized in that:

Step S3, gradient pressure step injection is divided into three stages;

The first stage, injecting resin at 30-40bar pressure to infiltrate the surface fabric for 20-25 s;

step two, boosting to 80-100bar to fill the middle mixed knitting layer and the bottom fabric, and soaking for 30-35 s;

the third stage of pressure maintaining is 100-120bar, ultrasonic vibration is synchronously applied in the whole injection process, the frequency is 25-30kHz, and the power is 60-80W.

5. The method for forming a lightweight automotive trim part according to claim 1, characterized in that:

the die cavity is provided with a self-adaptive diversion trench, the trench width changes with the gradient of the fiber volume fraction, wherein the trench width of the surface layer is 2mm, the trench width of the middle layer is 3mm, and the trench width of the bottom layer is 2.5mm.

6. The method for forming a lightweight automotive trim part according to claim 1, characterized in that:

The dual-gradient curing in the step S4 is divided into two stages, wherein the first stage is to apply 20kHz ultrasonic wave at 105-115 ℃ and keep the temperature for 70min, and the second stage is to apply 25kHz ultrasonic wave at 135-145 ℃ and cure for 45-55 min, and the whole curing process is to apply 0.15-0.25MPa pressure.

7. The method for forming a lightweight automotive trim part according to claim 1, characterized in that:

and S2, the gamma-aminopropyl triethoxy silane coupling agent generates hydroxyl through hydrolysis, and forms chemical bonding with nano montmorillonite and the hydroxyl on the surface of the fiber.

8. The method for forming a lightweight automotive trim part according to claim 5, characterized in that:

in the step S3, an elastic sealing element is arranged on the inner wall of the adaptive diversion trench, and the trench width is dynamically adjusted along with the pressure change during resin injection, so that the resin is ensured to flow along a preset path, and the fiber displacement is avoided.

9. The method for forming a lightweight automotive trim part according to claim 1, characterized in that:

In the step S3, the ultrasonic vibration direction is perpendicular to the resin flowing direction, the ultrasonic power is dynamically adjusted along with the injection stage, wherein the first stage is 60W, the second stage is 70W, and the third stage is 80W.