A composite material leaf spring and its molding method

Abstract

This application relates to a composite leaf spring and its molding method. A high-weft unidirectional continuous glass fiber cloth is laid in a molding mold, with the warp and weft weave ratio of the high-weft unidirectional continuous glass fiber cloth being less than or equal to the designed warp and weft ratio. PDCPD resin is poured into the molding mold; the molding mold is heated and pressurized to obtain the composite leaf spring. Using a high-weft unidirectional continuous glass fiber cloth, and ensuring that the warp and weft weave ratio of the high-weft unidirectional continuous glass fiber cloth is less than or equal to the designed warp and weft ratio, can reduce or even eliminate the need for nylon braided edge sealing. This effectively reduces fiber bundle aggregation and interlayer voids, thereby facilitating resin flow and impregnation. This improves the resin fiber distribution between composite layers, resulting in a denser interlayer bond and increased load-bearing capacity. Therefore, this application can solve the problem in related technologies where composite leaf springs molded using the VARTM process have uneven fiber distribution, low load-bearing capacity, and fail to meet the load-bearing requirements of composite leaf springs.

Description

Technical Field

[0001] This application relates to the field of automotive parts manufacturing technology, and in particular to a composite material leaf spring and its molding method. Background Technology

[0002] In response to the growing demand for lightweight and energy-saving automobiles, major domestic and international automakers are developing applications of composite material leaf springs to replace metal leaf springs.

[0003] The industrial production of composite leaf springs currently mainly adopts prepreg molding or HPRTM process (High Pressure Resin Transfer Molding, which is a molding process that uses high pressure to mix resin and inject it into a vacuum-sealed mold that is pre-laid with fiber reinforcement and pre-placed inserts. The resin flows through the mold, impregnates, cures and demolds to obtain composite material products).

[0004] When using prepreg molding or HPRTM process, the industrial production of composite leaf springs faces the problems of large equipment investment and high process cost. The price of its parts is generally 2-3 times that of metal leaf springs. The high cost makes it difficult to promote its application in the domestic commercial vehicle industry.

[0005] For example, some related technologies disclose the manufacturing process of FRP composite leaf springs. Specifically, step S1: fiber cloth weaving process, where the fiber cloth is pulled and woven by a loom, and different angle fiber cloths are woven according to the design requirements of the FRP composite leaf spring; step S2: fiber cloth stacking process, where the fiber cloth is cut into pieces of the same length but different widths, and stacked together according to the design requirements of the FRP composite leaf spring, with the middle fiber cloth being the widest, and the width of the upper and lower fiber cloths decreasing in a trapezoidal shape from both ends to the middle fiber cloth, with the middle fiber cloth being the shortest, and adhesive is evenly sprinkled between the fiber cloths, and fiber cloths of different angles are placed in designated layers to form a fiber cloth stack; step S3: stacking spot welding process, where two coaxial heating rods of equal diameter are heated to 150°~180° and their opposite ends sandwich the fiber cloth stack in the middle, and the adhesive, after being heated, bonds the fiber cloths together to form a weld point; step S4: preforming process, where the preform... Step S5: Cutting process. First, place the fiberboard on a pad with the same surface shape as the inner arch shape of the fiberboard. Use a cutting machine to cut the fiberboard into multiple pieces, each with a width consistent with the width of the FRP composite leaf spring body, forming multiple resin-free blanks. Step S6: HP-RTM process. Completed by HP-RTM molding mold, the resin-free blanks are placed into the mold cavity. The resin viscosity is adjusted according to the different resin characteristics. Then, the resin is injected into the mold cavity, and the mold is kept for a set time to allow the resin and fiber to solidify and form. Step S7: Unloading and shaping process. Open the mold cavity, take out the shaped blanks, and immediately install them on the fixing fixture to prevent the shaped blanks from deforming in all directions. After cooling, a shaped semi-finished product is formed. Step S8: Post-processing process. Remove the protrusions left on the shaped semi-finished product and remove the excess parts at both ends. Drill center blind holes at the top and bottom of the middle and drill through holes for mounting ears at both ends to form the finished FRP composite leaf spring body.

[0006] The aforementioned technologies employ the HPRTM process, which involves complex molding methods and high processing costs.

[0007] VARTM (Vacuum Assisted Resin Transfer Molding) is a novel, low-cost molding technology for producing large composite material parts. It has been widely used in industries such as wind power, aviation, and shipbuilding. However, because it does not involve pressure during the molding process, composite leaf springs produced by VARTM have problems such as uneven fiber distribution and low load-bearing capacity, which cannot meet the load-bearing requirements of composite leaf springs. Currently, there are no patents or application reports on the use of this process to prepare composite leaf springs. Summary of the Invention

[0008] This application provides a composite material leaf spring and its molding method to solve the problem that composite material leaf spring products molded by the VARTM process in related technologies have uneven fiber distribution, low load-bearing capacity, and cannot meet the load-bearing requirements of composite material leaf springs.

[0009] In a first aspect, a method for molding a composite material leaf spring is provided, comprising:

[0010] A high-weft unidirectional continuous glass fiber cloth is laid in a molding mold, wherein the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth is less than or equal to the designed warp and weft ratio;

[0011] PDCPD resin is poured into the molding die;

[0012] The molding die is heated and pressurized to obtain a composite material leaf spring.

[0013] In some embodiments, the design latitude-longitude ratio is 2% to 4%;

[0014] And / or, the pressure applied to the molding die during heating and pressurization is 3MPa to 5MPa, the mold temperature is 80℃ to 100℃, and the time is 15 to 25min.

[0015] In some embodiments, the dynamic viscosity of the PDCPD resin is less than or equal to a dynamic viscosity threshold, so that the PDCPD resin is a low dynamic viscosity resin.

[0016] In some embodiments, the dynamic viscosity threshold is 50 cp;

[0017] And / or, the dynamic viscosity of the PDCPD resin is 30cp to 50cp.

[0018] In some embodiments, before pouring PDCPD resin into the molding die, the molding method further includes: evacuating the molding die to a vacuum.

[0019] In some embodiments, the vacuum degree of the molding die is greater than or equal to 99.5 kPa.

[0020] In some embodiments, the PDCPD resin comprises component A and component B, wherein the mass ratio of component A to component B is 100:1 to 4, wherein:

[0021] Component A, by mass fraction, comprises: 95%–98% dicyclopentadiene, 0.5%–2% activator, and 1.5%–4.5% additives;

[0022] Component B, by mass fraction, comprises: 3%–5% catalyst, 90%–95% polymerization reaction regulator, and 2%–5% additives.

[0023] In some embodiments, the activator includes one or more of diethylaluminum and diethylzinc;

[0024] And / or, the additives in component A include one or more of dioctyl phthalate plasticizer and antioxidant 264;

[0025] And / or, the catalyst comprises a ruthenium carbene compound or a salt thereof;

[0026] And / or, the additives in component B include one or more of tetrahydrofuran stabilizers and decabromodiphenyl ether flame retardants;

[0027] And / or, the polymerization reaction regulator includes one or more of diethylene glycol dimethyl ether, triphenylphosphine, and triethyl phosphate.

[0028] In some embodiments, pouring PDCPD resin into the molding die includes the following steps:

[0029] Component A and component B are each injected into a mixing head through an injection head to obtain a mixture;

[0030] The mixture is injected into the molding die.

[0031] Secondly, a composite leaf spring is provided, which is obtained by the molding method of composite leaf springs as described above.

[0032] The beneficial effects of the technical solution provided in this application include:

[0033] This application provides a composite material leaf spring and its molding method. The molding method of the composite material leaf spring provided in this application uses a high-weft unidirectional continuous glass fiber cloth, and the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth is less than or equal to the designed warp and weft ratio. The advantage is that it can reduce the nylon braiding edge sealing of the warp braiding machine, or even eliminate the need for nylon braiding edge sealing, which can effectively reduce the aggregation of fiber bundles and interlayer gaps, thereby facilitating the flow and impregnation of resin. This can improve the resin fiber distribution between composite material layers, making the interlayer bonding denser and improving the load-bearing capacity. Therefore, the molding method of the composite material leaf spring provided in this application can solve the problem that composite material leaf spring products molded by the VARTM process in related technologies have uneven fiber distribution, low load-bearing capacity, and cannot meet the load-bearing requirements of composite material leaf springs.

[0034] For composite leaf springs formed by traditional VARTM process, there are many resin-rich areas, high porosity, and uneven fiber distribution. This can lead to fracture failure in the thickness direction, low load-bearing capacity and fatigue resistance, and an average bench life of 50,000 cycles.

[0035] The composite leaf springs obtained by the molding method of the composite leaf springs in this application have relatively uniform resin and fiber distribution, low porosity, and if failure occurs, it is mainly delamination failure, which is not easy to occur. They have high load-bearing capacity and fatigue resistance, and the average bench life can reach 200,000 cycles.

[0036] The solution provided in this application uses PDCPD resin and controls its dynamic viscosity to be less than or equal to the dynamic viscosity threshold, making the PDCPD resin a low dynamic viscosity resin. This results in good resin flowability, which is beneficial for molding large composite material products. Simultaneously, since the fiber cloth provided in this application is a high-weft unidirectional continuous glass fiber cloth, and the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth is less than or equal to the designed warp and weft ratio, when the injected PDCPD resin is a low dynamic viscosity resin, it can flow and impregnate better in the high-weft unidirectional continuous glass fiber cloth. This improves the resin fiber distribution between composite material layers, resulting in a denser interlayer bond and increased load-bearing capacity.

[0037] Before injecting PDCPD resin, this application evacuates the molding mold to a vacuum, then injects the resin using a negative pressure vacuum method, and then applies pressure and uses positive pressure holding molding. Compared with the traditional VARTM process where parts are molded under negative pressure, this application uses a combination of positive and negative pressure, which results in a higher density of fibers and resin in the product, a lower porosity, and a significant improvement in the product's mechanical properties and fatigue resistance.

[0038] Furthermore, this application employs an improved VARTM process that combines positive and negative pressure, which is also a VARTM process. Therefore, this application has the advantages of low equipment investment and low process cost, thereby reducing the price of composite material leaf spring parts. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 A flowchart illustrating the molding method of composite leaf springs provided in this application embodiment;

[0041] Figure 2 SEM cross-sectional view of a composite leaf spring formed by the traditional VARTM process;

[0042] Figure 3 SEM cross-sectional view of the composite material leaf spring provided in the embodiments of this application. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0044] This application provides a method for molding composite leaf springs, which can solve the problems of uneven fiber distribution and low load-bearing capacity in composite leaf spring products molded by VARTM process in related technologies, and thus cannot meet the load-bearing requirements of composite leaf springs.

[0045] This application provides a method for molding a composite material leaf spring, which includes the following steps:

[0046] 101: Lay high-weft unidirectional continuous glass fiber cloth in a molding mold, wherein the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth is less than or equal to the designed warp and weft ratio.

[0047] In step 101, the number of layers of high-weft unidirectional continuous glass fiber cloth can be selected according to actual needs. That is to say, several layers of high-weft unidirectional continuous glass fiber cloth can be laid in the molding mold.

[0048] 102: PDCPD resin is poured into the molding die.

[0049] 103: The molding die is heated and pressurized to obtain a composite material leaf spring.

[0050] The molding method for composite leaf springs provided in this application uses high-weft unidirectional continuous glass fiber cloth, and the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth is less than or equal to the designed warp and weft ratio. The advantage is that it can reduce the nylon braiding edge sealing of the warp braiding machine, or even eliminate the need for nylon braiding edge sealing, which can effectively reduce the aggregation of fiber bundles and interlayer gaps, thereby facilitating the flow and impregnation of resin. This can improve the resin fiber distribution between composite material layers, making the interlayer bonding denser and the load-bearing capacity improved. Therefore, the molding method for composite leaf springs provided in this application can solve the problem of uneven fiber distribution and low load-bearing capacity in composite leaf spring products molded by VARTM process in related technologies, which cannot meet the load-bearing requirements of composite leaf springs.

[0051] See Figure 2 As shown, Figure 2The image shows a SEM cross-section of a composite leaf spring formed using the traditional VARTM process. As can be seen from the image, there are many resin-rich areas, high porosity, and uneven fiber distribution. This can lead to fracture failure in the thickness direction, resulting in low load-bearing capacity and fatigue resistance, with an average bench life of 50,000 cycles.

[0052] See Figure 3 As shown, Figure 3 The image shows a SEM cross-sectional view of the composite leaf spring obtained by the molding method of the composite leaf spring in this application. As can be seen from the image, the resin and fiber are relatively uniformly distributed, the porosity is low, and if failure occurs, it is mainly delamination failure, which is not easy to occur. The load-bearing capacity and fatigue resistance are high, and the average bench life can reach 200,000 cycles.

[0053] In step 101 above, in order to effectively reduce the aggregation of fiber bundles and interlayer voids by increasing the weft ratio of the fiber cloth and reducing the warp ratio of the fiber cloth, thereby facilitating the flow and impregnation of resin, the resin fiber distribution between composite material layers can be improved, making the interlayer bonding denser and the load-bearing capacity improved. In some preferred embodiments, the above-mentioned warp-weft ratio can be set to 2% to 4%.

[0054] It is understood that by making the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth less than or equal to 2% to 4%, the aggregation of fiber bundles and interlayer voids can be effectively reduced, which is conducive to the flow and impregnation of resin. This can improve the resin fiber distribution between composite material layers, making the interlayer bonding denser and the load-bearing capacity improved.

[0055] Furthermore, as a preferred embodiment, the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth can be selected according to the actual situation. For example, as an example, the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth is less than or equal to 2%. Further, as a preferred example, the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth is 2%.

[0056] It should be noted that, in step 101 above, before laying the high-weft unidirectional continuous glass fiber cloth in the molding mold, the high-weft unidirectional continuous glass fiber cloth can also be surface treated with a polyolefin sizing agent.

[0057] Since the currently known composite leaf springs mainly use epoxy resin and polyurethane materials, which have high dynamic viscosity, usually ≥200cp, their fluidity is insufficient. When using RTM (Resin Transfer Molding) process to mold thick parts (e.g., parts with a thickness >40mm), there will be quality problems such as uneven wetting and insufficient pouring. In view of this, this application has optimized the resin used to solve this problem.

[0058] Specifically, in step 102 above, the PDCPD resin (i.e., polydicyclopentadiene resin) injected into the molding die has a dynamic viscosity less than or equal to the dynamic viscosity threshold, so that the PDCPD resin is a low dynamic viscosity resin.

[0059] The solution provided in this application uses PDCPD resin and controls its dynamic viscosity to be less than or equal to the dynamic viscosity threshold, so that the PDCPD resin is a low dynamic viscosity resin, thereby making the PDCPD resin have good resin flowability, which is beneficial for molding large composite material products.

[0060] Meanwhile, the fiber cloth provided in this application is a high-weft unidirectional continuous glass fiber cloth, and the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth is less than or equal to the designed warp and weft ratio, thereby effectively reducing the aggregation of fiber bundles and interlayer voids, which is conducive to the flow and impregnation of resin. When the injected PDCPD resin is a low dynamic viscosity resin, it can flow and impregnate better in the high-weft unidirectional continuous glass fiber cloth, thereby further improving the resin fiber distribution between composite material layers, making the interlayer bonding denser and improving the load-bearing capacity.

[0061] In order to make the PDCPD resin with low dynamic viscosity and thus good resin flowability, in some preferred embodiments, the dynamic viscosity threshold can be determined according to actual needs. For example, the dynamic viscosity threshold is 50 cp.

[0062] It is understood that controlling the dynamic viscosity of the PDCPD resin to be less than or equal to 50 cp can make the PDCPD resin a low dynamic viscosity resin, thereby giving the PDCPD resin good resin flowability, which is beneficial for molding large composite material products.

[0063] Furthermore, the dynamic viscosity of the PDCPD resin can be selected according to actual conditions. For example, as an example, the dynamic viscosity of the PDCPD resin is 30 cp to 50 cp. Further, as a preferred example, the dynamic viscosity of the PDCPD resin is 40 cp.

[0064] In step 102 above, low dynamic viscosity PDCPD resin can be infused using the RIM process (reaction injection molding, or RIM for short).

[0065] The injected PDCPD resin comprises component A and component B, with a mass ratio of component A to component B of 100:1 to 4, wherein:

[0066] Component A, by mass fraction, comprises: 95%–98% dicyclopentadiene, 0.5%–2% activator, and 1.5%–4.5% additives;

[0067] Component B, by mass fraction, comprises: 3%–5% catalyst, 90%–95% polymerization reaction regulator, and 2%–5% additives.

[0068] The activator includes one or more of diethylaluminum and diethylzinc; for example, a diethylaluminum / diethylzinc composite activator is used.

[0069] The additives in component A include one or more of dioctyl phthalate plasticizer and antioxidant 264;

[0070] The catalyst includes ruthenium carbene compounds or salts thereof;

[0071] The additives in component B include one or more of tetrahydrofuran stabilizers and decabromodiphenyl ether flame retardants.

[0072] The polymerization reaction regulator includes one or more of diethylene glycol dimethyl ether, triphenylphosphine, and triethyl phosphate. It mainly controls the polymerization reaction time, prevents the reaction from being too fast, and avoids premature gel polymerization of the resin before it has flowed sufficiently in the mold.

[0073] Specifically, pouring PDCPD resin into the molding die includes the following steps:

[0074] 201: Using a RIM machine, components A and B are injected into a mixing head separately through an injection head at a mass ratio of 100:1 to 4 to obtain a mixture;

[0075] 202: Then, use the mixing head of the RIM machine to inject the mixture into the molding die.

[0076] For step 103 above, an improved VARTM molding process can be used to form the part.

[0077] Specifically, before injecting PDCPD resin into the molding die, the molding method further includes: evacuating the molding die to a vacuum.

[0078] The vacuum degree of the molding die can be determined according to actual needs. For example, the vacuum degree of the molding die is greater than or equal to 99.5 kPa.

[0079] Under the negative pressure of a vacuum, the mixture can be drawn into the molding die.

[0080] Afterwards, the inlet and outlet are closed, the molding die is heated and pressurized, and then allowed to cool naturally for a period of time, such as 30 minutes. The die is then opened, the product is removed, and the composite material leaf spring is obtained.

[0081] The pressure applied to the molding die during heating and pressurization is 3MPa to 5MPa, the mold temperature is 80℃ to 100℃, and the time is 15 to 25 minutes.

[0082] As can be seen, before injecting PDCPD resin, this application evacuates the molding mold to a vacuum, then injects the resin through negative pressure vacuum, and then applies pressure and molds by positive pressure holding. Compared with the traditional VARTM process where parts are molded under negative pressure, this application adopts an improved VARTM process that combines positive and negative pressure, which results in a higher density of fibers and resin, lower porosity, and significantly improved mechanical properties and fatigue resistance of the product.

[0083] Furthermore, this application employs an improved VARTM process that combines positive and negative pressure, which is also a VARTM process. Therefore, this application has the advantages of low equipment investment and low process cost, thereby reducing the price of composite material leaf spring parts.

[0084] In step 101 above, the high-density unidirectional continuous glass fiber cloth is cut according to the size of the composite leaf spring parts and placed into the molding mold, and the mold is closed. When closing the mold, the molding mold is reserved with a certain gap according to the amount of glue injected (i.e. the amount of component A and component B injected into the molding mold). The specific gap size can be determined according to actual needs. For example, as an example, the molding mold is reserved with a gap of 0.8mm to 1.5mm.

[0085] In step 103 above, when applying pressure to the molding die, it is necessary to compact the gap reserved in the molding die.

[0086] The molding die uses a double-layer sealing strip. The first layer of sealing strip ensures the sealing of the vacuum flow process, and the second layer of sealing strip ensures the sealing of the molding process.

[0087] Example 1

[0088] The composite material leaf spring provided in Example 1 is a rear auxiliary spring for a medium-sized truck. Its three-dimensional dimensions are: length 1150mm, width 60mm, and gradually varying thickness 32-40mm. Its molding method includes the following steps:

[0089] 101: Lay high-weft unidirectional continuous glass fiber cloth in a molding mold, wherein the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth is less than or equal to the designed warp and weft ratio.

[0090] 102: PDCPD resin is poured into the molding die.

[0091] 103: The molding die is heated and pressurized to obtain a composite material leaf spring.

[0092] In step 101 above, the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth is 2%.

[0093] In step 101 above, the high-density unidirectional continuous glass fiber cloth is cut according to the size of the composite material leaf spring parts and placed into the molding mold, and the mold is closed. When closing the mold, a 1.0mm gap is reserved in the molding mold.

[0094] In step 101 above, the molding die uses a double-layer sealing strip. The first layer of sealing strip ensures the sealing of the vacuum flow process, and the second layer of sealing strip ensures the sealing of the molding process.

[0095] In step 102 above, the dynamic viscosity of the injected PDCPD resin is 40 cp, and the PDCPD resin includes component A and component B, with a mass ratio of component A to component B of 100:2, wherein:

[0096] Component A, by mass fraction, comprises: 95% dicyclopentadiene, 2% activator, and 3% additives;

[0097] Component B, by mass fraction, comprises: 3% catalyst, 95% polymerization reaction regulator, and 2% additives.

[0098] The activator used is a diethylaluminum / diethylzinc composite activator.

[0099] The additive in component A is dioctyl phthalate plasticizer;

[0100] The catalyst is a ruthenium carbene compound;

[0101] The additive in component B is a tetrahydrofuran stabilizer;

[0102] The polymerization reaction regulator is a mixture of triphenylphosphine and triethyl phosphate.

[0103] In step 102 above, pouring PDCPD resin into the molding die includes the following steps:

[0104] 201: Using a RIM machine, components A and B are injected into the mixing head separately through an injection head at a mass ratio of 100:2 to obtain a mixture;

[0105] 202: Then, use the mixing head of the RIM machine to inject the mixture into the molding die.

[0106] In step 103 above, the part is formed using an improved VARTM molding process.

[0107] Specifically, before injecting PDCPD resin into the molding die, the molding method further includes: evacuating the molding die to a vacuum level. The vacuum level of the molding die is greater than or equal to 99.5 kPa.

[0108] During injection, the mixture is drawn into the molding mold through vacuum negative pressure.

[0109] In step 103 above, the pressure applied to the molding die during heating and pressurization is 4 MPa, the mold temperature is 100°C, and the time is 20 min. After the 20 min reaction is completed, allow it to cool naturally for 30 min, then open the mold and remove the PDCPD composite leaf spring.

[0110] Comparative Example 1

[0111] Comparative Example 1: Epoxy resin composite leaf springs obtained using conventional compression molding processes.

[0112] Table 1: Performance and bench test results of Example 1 and Comparative Example 1

[0113]

[0114]

[0115] The above tests prove that the performance of PDCPD composite leaf springs is comparable to that of mass-produced molded epoxy resin composite leaf springs. The parts have undergone 240,000 bench tests without any abnormalities, which can meet the requirements for use of leaf spring parts.

[0116] Comparative Example 2

[0117] The difference between this comparative example and Example 1 is that: a commercially available unidirectional continuous glass fiber cloth is used, which is sewn with polyester stitch-knitted thread in the warp direction, with a warp-to-weft weave ratio >10%. Everything else is the same as in Example 1. Samples of the prepared composite leaf spring were taken and tested, and the results are as follows:

[0118] Table 2: Performance Comparison of Example 1 and Comparative Example 2

[0119]

[0120] The material test results of Comparative Example 2 show that the mechanical properties of commercially available unidirectional continuous glass fiber cloth are lower than those of high-weft unidirectional continuous glass fiber cloth composites, especially the interlaminar shear strength, which fails to meet the technical requirements for composite leaf spring parts. This is mainly due to the higher content of warp polyester seam threads, which have a stronger binding effect on the glass fiber, resulting in a clear boundary between the composite fiber and resin layers and a decrease in shear strength.

[0121] Comparative Example 3

[0122] The difference between this comparative example and Example 1 is that the VARTM process without positive pressure was used, i.e., no 4MPa pressure was applied. Everything else was the same as in Example 1. Samples of the prepared composite leaf springs were taken and tested, and the results are as follows:

[0123] Table 3. Performance comparison of Example 1 and Comparative Example 3

[0124]

[0125] As can be seen from the material test results of Comparative Example 3, the mechanical properties of VARTM-molded high-strength unidirectional continuous glass fiber cloth PDCPD composite material, such as tensile, bending, and vertical compression, are basically equivalent to those of the technical solution of this application. However, due to the lack of molding, the bonding density between the fiber and the resin in the thickness direction of the material is not sufficient, resulting in a 10% lower interlaminar shear strength.

[0126] Example 2

[0127] The composite material leaf spring provided in this embodiment 2 is a rear spring for a heavy-duty tractor vehicle. Its three-dimensional dimensions are: length 1550mm, width 70mm, and a gradually changing thickness of 65-80mm. Parts of this thickness cannot be molded using HP-RTM or VARTM processes. The molding method in this embodiment includes the following steps:

[0128] 101: Lay high-weft unidirectional continuous glass fiber cloth in a molding mold, wherein the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth is less than or equal to the designed warp and weft ratio.

[0129] 102: PDCPD resin is poured into the molding die.

[0130] 103: The molding die is heated and pressurized to obtain a composite material leaf spring.

[0131] In step 101 above, the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth is 1%.

[0132] In step 101 above, the high-density unidirectional continuous glass fiber cloth is cut according to the size of the composite material leaf spring parts and placed into the molding mold, and the mold is closed. When closing the mold, a 1.5mm gap is reserved in the molding mold.

[0133] In step 101 above, the molding die uses a double-layer sealing strip. The first layer of sealing strip ensures the sealing of the vacuum flow process, and the second layer of sealing strip ensures the sealing of the molding process.

[0134] In step 102 above, the dynamic viscosity of the injected PDCPD resin is 30 cp, and the PDCPD resin includes component A and component B, with a mass ratio of component A to component B of 100:2, wherein:

[0135] Component A, by mass fraction, comprises: 95% dicyclopentadiene, 1.5% activator, and 3.5% additives;

[0136] Component B, by mass fraction, comprises: 3% catalyst, 95% polymerization reaction regulator, and 2% additives.

[0137] The activator used is a diethylaluminum / diethylzinc composite activator.

[0138] The additive in component A is dioctyl phthalate plasticizer;

[0139] The catalyst is a ruthenium carbene compound;

[0140] The additive in component B is a tetrahydrofuran stabilizer;

[0141] The polymerization reaction regulator is a mixture of triphenylphosphine and triethyl phosphate.

[0142] In step 102 above, pouring PDCPD resin into the molding die includes the following steps:

[0143] 201: Using a RIM machine, components A and B are injected into the mixing head separately through an injection head at a mass ratio of 100:2 to obtain a mixture;

[0144] 202: Then, use the mixing head of the RIM machine to inject the mixture into the molding die.

[0145] In step 103 above, the part is formed using an improved VARTM molding process.

[0146] Specifically, before injecting PDCPD resin into the molding die, the molding method further includes: evacuating the molding die to a vacuum level. The vacuum level of the molding die is greater than or equal to 99.5 kPa.

[0147] During injection, the mixture is drawn into the molding mold through vacuum negative pressure.

[0148] In step 103 above, the pressure applied to the molding die during heating and pressurization is 5 MPa, the mold temperature is 100°C, and the time is 25 min. After the 25 min reaction is completed, allow it to cool naturally for 30 min, then open the mold and remove the PDCPD composite leaf spring.

[0149] Existing HP-RTM and VARTM processes cannot mold thick parts because the resin cannot flow sufficiently within the mold to impregnate the fibers. Therefore, prepreg molding is mainly used. Compared to prepreg molding, this technical solution produces parts with comparable performance but at a lower material and process cost, making it a more economical alternative.

[0150] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application 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, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0151] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0152] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for molding a composite material leaf spring, characterized in that, It includes: A high-weft unidirectional continuous glass fiber cloth is laid in a molding mold, wherein the warp and weft weaving ratio of the high-weft unidirectional continuous glass fiber cloth is less than or equal to the designed warp and weft ratio; PDCPD resin is poured into the molding die; The molding die is heated and pressurized to obtain a composite material leaf spring.

2. The molding method of the composite material leaf spring as described in claim 1, characterized in that: The design latitude-longitude ratio is 4%; And / or, the pressure when heating and pressurizing the molding die is 3MPa~5MPa, the mold temperature is 80℃~100℃, and the time is 15~25min.

3. The molding method of the composite material leaf spring as described in claim 1, characterized in that: The dynamic viscosity of the PDCPD resin is less than or equal to the dynamic viscosity threshold, so that the PDCPD resin is a low dynamic viscosity resin.

4. The molding method of the composite material leaf spring as described in claim 3, characterized in that: The dynamic viscosity threshold is 50 cP; And / or, the dynamic viscosity of the PDCPD resin is 30 cP to 50 cP.

5. The molding method of the composite material leaf spring as described in claim 1, characterized in that: Before injecting PDCPD resin into the molding die, the molding method further includes: evacuating the molding die to a vacuum.

6. The molding method of the composite material leaf spring as described in claim 5, characterized in that: The vacuum degree of the molding die is greater than or equal to 99.5 kPa.

7. The molding method of the composite material leaf spring as described in claim 1, characterized in that, The PDCPD resin comprises component A and component B, with a mass ratio of component A to component B of 100:1~4, wherein: Based on mass fraction, component A comprises: 95%–98% dicyclopentadiene, 0.5%–2% activator, and 1.5%–4.5% additives; Component B, by mass fraction, includes: 3%~5% catalyst, 90%~95% polymerization reaction regulator, and 2%~5% additives.

8. The molding method of the composite material leaf spring as described in claim 7, characterized in that: The activator includes one or more of diethylaluminum and diethylzinc; And / or, the additives in component A include one or more of dioctyl phthalate plasticizer and antioxidant 264; And / or, the catalyst comprises a ruthenium carbene compound or a salt thereof; And / or, the additives in component B include one or more of tetrahydrofuran stabilizers and decabromodiphenyl ether flame retardants; And / or, the polymerization reaction regulator includes one or more of diethylene glycol dimethyl ether, triphenylphosphine, and triethyl phosphate.

9. The molding method of the composite material leaf spring as described in claim 7, characterized in that: The process of pouring PDCPD resin into the molding die includes the following steps: Component A and component B are each injected into a mixing head through an injection head to obtain a mixture; The mixture is injected into the molding die.

10. A composite material leaf spring, characterized in that: It is obtained by the molding method of composite leaf spring as described in any one of claims 1 to 9.

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