Injection molding process for composite material luggage

Abstract

The invention relates to the technical field of bags and suitcases, and discloses a composite material bag injection molding process which comprises the following steps: S1, providing a composite material prefabricated part which sequentially comprises a reinforced fiber layer, a function response layer and a buffer supporting layer; s2, the composite material prefabricated part is placed in a first mold cavity to be heated, so that the composite material prefabricated part is softened and preliminarily shaped in the mold cavity; s3, the heated composite prefabricated part is transferred into a second mold cavity, a molten thermoplastic material is injected into the second mold cavity, and a magnetic field and thermal excitation are synchronously applied in the injection molding process; and S4, after the injection molding process is completed, cooling treatment is conducted on the second mold cavity, and the formed composite material bag is taken out of the second mold cavity. By optimizing the formula and the proportion of each layer of the composite material and accurately controlling the effects of heating, thermal excitation and a magnetic field, the shape recovery capability, the thermal responsiveness and the impact resistance of the luggage are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of luggage, and specifically to an injection molding process for composite material luggage cases. Background Art

[0002] Composite material luggage cases are widely used in daily life. Due to their characteristics such as light weight, durability, waterproofness, and impact resistance, they have become an important choice in the modern luggage industry. As consumers' requirements for the functionality and durability of luggage cases continue to increase, composite material luggage cases have gradually adopted multi-layered and functional design structures. Especially in the outer shell part of the luggage case, using composite materials can not only provide high-strength support, but also achieve shape memory and thermal response characteristics, enabling the luggage case to automatically return to its original state when subjected to external pressure or temperature changes.

[0003] The injection molding process is a commonly used processing method in the manufacturing of composite material luggage cases. It heats the thermoplastic material to a molten state, injects it into the mold, and cools it to form. This process can not only achieve large-scale production, but also has good molding accuracy and surface finish. However, in the traditional injection molding process, although rapid material forming can be achieved, there are often some technical bottlenecks, especially in the multi-layer structure design of composite materials and the improvement of functional response performance.

[0004] In the prior art, the manufacturing of composite material luggage cases mostly relies on simple single materials or multi-layer designs lacking precise ratios, resulting in insufficient tightness in the performance connection between materials. Especially, the synergistic effect among the reinforcing fiber layer, functional response layer, and buffer support layer is insufficient. Although the composite materials designed in this way have certain mechanical properties and impact resistance, in actual applications, due to the performance mismatch between the layers of materials, the durability and shape recovery ability of the luggage case are poor. In addition, the control of heating, thermal excitation, and magnetic field action in the prior art has not reached the optimal balance, resulting in certain limitations in shape memory performance and thermal response, and it is difficult to fully meet the requirements of modern luggage cases for intelligence and high performance.

[0005] Therefore, the present invention proposes an injection molding process for composite material luggage cases to solve the deficiencies of the prior art. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention provides an injection molding process for composite material luggage cases, which solves the problems of poor shape recovery ability and poor thermal response caused by unreasonable material hierarchical structure, performance mismatch, and insufficient control of thermal excitation and magnetic field action.

[0007] To achieve the above objectives, the present invention is realized through the following technical solutions: An injection molding process for composite material luggage cases includes the following steps:

[0008] S1. Providing a composite material preform, wherein the preform comprises a reinforcing fiber layer, a functional response layer and a buffer support layer in sequence;

[0009] By providing a preform of a multi-layer composite structure, the preform includes a reinforcing fiber layer, a functional response layer and a buffer support layer in sequence. The reinforcing fiber layer provides a good structural strength and rigidity foundation, the functional response layer introduces magnetic response materials and activatable polymers to achieve external field response control in subsequent injection molding, and the buffer support layer plays a role in deformation absorption and stress relief during the injection molding process. This layered design ensures the coordinated performance of the various functions of the structure in the subsequent molding process, laying the foundation for the overall molding quality and functionality.

[0010] S2, placing the composite material preform into the first mold cavity for heating treatment to soften it and preliminarily shape it in the mold cavity;

[0011] The composite material preform is placed in the first mold cavity for heating treatment to soften and bond the matrix resin between the layers, and the preform is initially shaped in the mold cavity. Through this step, the composite structure can achieve reconstruction of the internal bonding interface while maintaining the shape integrity, thereby improving the dimensional stability and interface adaptability of the preform during subsequent injection molding. This preheating molding process not only enhances the integrity of the multilayer structure, but also provides the necessary shape constraints for the external field response of the functional response layer during the injection molding process.

[0012] S3, transferring the heated composite preform to a second mold cavity, injecting molten thermoplastic material into the second mold cavity, and simultaneously applying a magnetic field and thermal excitation during the injection molding process;

[0013] After the initial heating and shaping, the composite preform is quickly transferred to the second mold cavity, and the molten thermoplastic material is injected into the mold cavity through the injection molding system to coat the preform. During the injection molding, a magnetic field and a thermal excitation field are synchronously applied in the mold cavity. Through the action of the magnetic field, the magnetic response particles in the preform are directional distributed, enhancing their functional coupling in the molded structure; at the same time, thermal excitation activates and directional migrates the polymer segments in the functional response layer, which is helpful for interface bonding and microstructure reconstruction. This process controls the multi-scale response behavior of the material interface through the coupling energy field, so that injection molding is no longer just a mechanical coating process, but a process of co-evolution of interface functions, which is the key innovation link of the present invention.

[0014] S4. After the injection molding process is completed, the second mold cavity is cooled and the molded composite material bag is taken out from the second mold cavity.

[0015] After injection molding, the second mold cavity is cooled by a cooling system. During the cooling process, while maintaining the cavity pressure, the composite material gradually solidifies and takes shape inside. Controlling the temperature drop helps to balance the stress release process between the multi-layer structures, avoiding interface peeling or internal stress concentration. After the cavity temperature drops to an appropriate range, the molded composite material luggage is taken out through a demolding mechanism. This process ensures stable solidification of the structure while maintaining the morphological coordination and functional integrity between the functional response layer and the thermoplastic coating layer, further guaranteeing the comprehensive performance of the product during actual use.

[0016] Preferably, in the step S1, the reinforcing fiber layer, by mass parts, comprises 30 - 70 parts of carbon fiber, 20 - 50 parts of a thermoplastic resin matrix, 2 - 10 parts of a wear-resistant additive, and 1 - 5 parts of a surface treatment agent;

[0017] The thermoplastic resin matrix is one of polyamide 6, polypropylene, or polyether ether ketone.

[0018] As a reinforcing fiber, carbon fiber accounts for 30 - 70 parts by mass, having a relatively high specific strength and specific stiffness, enabling the composite material to have strong tensile strength and impact resistance while maintaining its lightweight characteristics. The good combination of carbon fiber and the thermoplastic resin matrix ensures the structural stability of the composite material after molding and its excellent mechanical properties during use.

[0019] The role of the thermoplastic resin matrix in the reinforcing fiber layer is to act as a binder to firmly combine carbon fiber with other components. The selection of this resin matrix has an important impact on the processing performance and final forming effect of the reinforcing fiber layer. In the present invention, one of polyamide 6, polypropylene, or polyether ether ketone is selected as the thermoplastic resin matrix. These materials have good thermal stability and relatively low melting temperatures, making the injection molding process easier to operate. At the same time, they have good compatibility with the reinforcing fibers, effectively improving the mechanical properties and long-term durability of the composite material.

[0020] In order to improve the wear resistance and durability of the reinforcing fiber layer, the present invention also adds a wear-resistant additive to this layer, which accounts for 2 - 10 parts by mass. The wear-resistant additive can improve the wear resistance of the surface of the composite material while also enhancing its processability. By reasonably adding the wear-resistant additive, the wear of the composite material during use can be effectively reduced, thereby extending the service life of the luggage.

[0021] In addition, the addition of the surface treatment agent further improves the interfacial bonding force between the reinforcing fiber and the resin matrix, which accounts for 1 to 5 parts by mass. The surface treatment agent can change the physical and chemical properties of the fiber surface, making the bonding between the fiber and the matrix resin more firm, thus avoiding problems such as material delamination or fracture caused by poor interfacial bonding during the molding process. The surface treatment method plays a crucial role in enhancing the overall performance of the composite material.

[0022] By precisely controlling the ratio and selection of carbon fiber and resin matrix, the reinforcing fiber layer can not only provide strong structural support but also ensure its long-term stability in complex usage environments. Especially the synergistic effect of wear-resistant additives and surface treatment agents enhances the surface strength and anti-aging ability of the composite material, ensuring that the luggage is not easily damaged under multiple actions such as friction and impact. The optimized design of this layer effectively improves the overall performance of the composite material, making it excellent in load-bearing and durability.

[0023] Preferably, in the step S1, the functional response layer, by mass, includes 20 to 60 parts of shape memory polymer, 10 to 30 parts of magnetic response particles, 10 to 40 parts of elastic matrix, 1 to 5 parts of dispersant, and 1 to 3 parts of heat stabilizer;

[0024] The magnetic response particles have a particle size of 10 to 100 nanometers and are coated with a silane-based dispersion coating on the surface.

[0025] This layer is mainly composed of shape memory polymer, magnetic response particles, elastic matrix, dispersant, heat stabilizer, etc., aiming to endow the composite material with intelligent response ability under external stimuli, especially the ability to deform or adjust its performance under the action of external magnetic field or thermal excitation. The design of this layer enables the composite material to not only have the basic physical protection function but also make dynamic responses according to external environmental changes, having a certain self-adaptive performance.

[0026] The core component of the functional response layer is the shape memory polymer, which accounts for 20 to 60 parts by mass. The addition of the shape memory polymer enables the composite material to automatically return to a predetermined shape or change its shape under the action of temperature, pressure or other external stimuli. This property can make the luggage self-recover to its initial shape when it is subjected to external impact or deformation, thereby improving the compressive resistance and durability of the luggage. The selection of the shape memory polymer has a decisive influence on its response performance. Preferably, materials such as polyurethane and polyester are selected, which can change their shapes within a specific temperature range and can effectively maintain the deformation memory.

[0027] In addition, the present invention introduces magnetic-responsive particles as an important component of the functional response layer, which accounts for 10 to 30 parts by mass. The magnetic-responsive particles can rapidly change their orientation or position under the action of an external magnetic field, thereby affecting the mechanical properties or shape of the composite material. To enhance the stability and dispersibility of the magnetic-responsive particles, the particle size is controlled between 10 and 100 nanometers, and a silane-based dispersion coating is coated on the surface. The addition of the silane coating can effectively prevent the agglomeration of magnetic-responsive particles in the matrix, ensuring their uniform distribution and stability throughout the composite material. At the same time, it also improves the compatibility between the magnetic-responsive particles and the polymer matrix, thereby enhancing the comprehensive properties of the material.

[0028] To ensure the structural integrity and good processability of the functional response layer, the present invention also introduces an elastic matrix, a dispersant, and a heat stabilizer. The addition of the elastic matrix endows the functional response layer with certain flexibility and elasticity, avoiding brittle fracture of the material after being stressed. The dispersant can ensure the uniform distribution of magnetic-responsive particles and shape memory polymers in the matrix, preventing non-uniform performance during the molding process. The addition of the heat stabilizer ensures that the functional response layer can still maintain its stability and functionality under high temperature or long-term exposure, avoiding a decline or failure of the material performance due to heat load.

[0029] Through the multi-material system of the functional response layer, the composite material is endowed with more complex response characteristics, especially the self-adaptive ability under external magnetic fields and thermal stimuli. Compared with traditional materials, this layer design enables the composite material to respond more precisely to external stimuli through the synergistic effect of shape memory polymers and magnetic-responsive particles, not only improving the compressive and impact resistance of the luggage, but also realizing intelligent dynamic adjustment during use.

[0030] The combination of shape memory polymers and magnetic-responsive particles enables the functional response layer to optimize the overall performance of the composite material through deformation or self-adaptive adjustment under mechanical loads and environmental changes. The addition of the dispersant and heat stabilizer further ensures the stability and reliability of this layer under high temperature, strong magnetic field, and long-term use conditions, avoiding functional failure or performance degradation.

[0031] Preferably, in the step S1, the buffer support layer, by mass, includes 40 to 80 parts of thermoplastic elastomer, 5 to 15 parts of foaming agent, 5 to 20 parts of impact modifier, 2 to 8 parts of compatibilizer, and 1 to 3 parts of anti-aging agent.

[0032] The main component of the buffer support layer is thermoplastic elastomer, which accounts for 40 to 80 parts by mass. The addition of thermoplastic elastomer makes the layer have good elasticity and flexibility, and it can also effectively absorb energy when subjected to external impact or pressure, reducing the impact of external force transmitted to the main body of the bag. Thermoplastic elastomer is plastic, can be molded under high temperature conditions, and return to its original shape after cooling. Therefore, using thermoplastic elastomer as the main component of the buffer support layer not only helps to improve the impact resistance of the bag, but also helps to ensure good processing performance during the molding process.

[0033] In order to enhance the shock-absorbing effect of the buffer support layer, the present invention also introduces a foaming agent, which accounts for 5 to 15 parts by mass. The introduction of the foaming agent enables the buffer support layer to have a certain porous structure, which can absorb external impact force through the compression and expansion of bubbles when subjected to force. The foaming structure can not only effectively reduce the density of the material, but also further improve the elasticity and buffering performance of the layer, and enhance its energy absorption capacity under external impact. By reasonably controlling the type and amount of the foaming agent, the hardness and elasticity of the buffer layer can be accurately adjusted to ensure the optimal buffering effect of the composite material.

[0034] In addition, the addition of impact modifiers can improve the impact resistance of the buffer support layer while improving its low temperature resistance. The impact modifier accounts for 5 to 20 parts by mass, and its function is to enhance the material's resistance to fracture and deformation under impact loads. Especially in low temperature environments, impact modifiers can prevent the material from becoming brittle and ensure the long-term stability of the composite material in various environments. The introduction of this modifier is a key innovation of the present invention in improving the performance of composite luggage. By optimizing the formula, the material can perform better under complex conditions.

[0035] The addition of compatibilizer accounts for 2 to 8 parts by mass, and its main function is to improve the compatibility and interface bonding strength between different components. In composite materials, the compatibility of components such as thermoplastic elastomers, foaming agents and impact modifiers directly affects the molding quality and the overall performance of the material. The use of compatibilizer can effectively promote the dispersion and uniform fusion of the components, and avoid performance differences or peeling caused by poor material interface during the molding process. Therefore, reasonable configuration of compatibilizer is an important link to ensure the high performance of composite materials.

[0036] Finally, the addition of anti-aging agent (1 to 3 parts by mass) further enhances the durability of the buffer support layer. Anti-aging agent can effectively prevent the degradation or performance decline of the material during long-term use, especially under the influence of environmental factors such as ultraviolet radiation and heat load. Anti-aging agent can protect the material from adverse reactions such as oxidation and pyrolysis, thereby extending the service life of the composite material and ensuring its stable performance in long-term use.

[0037] Through the synergistic effect of multiple components, the buffer support layer of the present invention achieves excellent performance of the material under various environmental conditions. The thermoplastic elastomer provides basic elasticity and flexibility. The introduction of the foaming agent enhances the shock absorption effect between layers. The impact modifier improves the stability of the material under impact loads. The compatibilizer ensures good bonding between the components. And the addition of the anti-aging agent guarantees the durability of the material during long-term use.

[0038] Compared with traditional materials, the buffer support layer of the present invention optimizes the component ratio and adds multifunctional modifiers, enabling the material to maintain stable performance under various environmental conditions such as high-intensity impact, low temperature, and ultraviolet rays. In addition, the application of the foaming agent further reduces the density of the material while enhancing the buffer performance and shock absorption effect, making the composite material luggage have better impact resistance and comfort during use.

[0039] Preferably, the thickness ratio of the reinforcing fiber layer, the functional response layer, and the buffer support layer is 2:1:1 to 4:3:2, and the total thickness is 1.5 to 3.0 millimeters.

[0040] The thickness ratio of the reinforcing fiber layer, the functional response layer, and the buffer support layer is 2:1:1 to 4:3:2, and the total thickness is 1.5 to 3.0 millimeters. This design is optimized according to the functional requirements of each layer to ensure that the composite material can meet multiple performance requirements during use while maintaining the lightweight and structural stability of the material.

[0041] First of all, the reinforcing fiber layer has the largest thickness proportion in the overall composite material, providing the material with basic strength and rigidity. By designing its thickness in the ratio of 2:1:1 to 4:3:2, it is ensured that while the reinforcing fiber layer provides sufficient rigidity, it will not make the material too rigid and affect the adaptability of other layers. The strength support of this layer is the basis for the impact resistance and load-bearing capacity of the material.

[0042] Secondly, the functional response layer has a relatively thin thickness and is in the middle position. Its main function is to achieve self-adaptive changes in shape or performance under the action of external stimuli (such as temperature changes or magnetic fields). The design of its thickness not only ensures that the functional response layer can sensitively respond to external environmental changes but also does not make it too thick to affect the structure and function of other layers, ensuring the overall coordination of the composite material.

[0043] Finally, the buffer support layer is responsible for providing shock absorption and impact resistance. By appropriately designing the thickness of the buffer layer, it can not only absorb external impacts but also avoid being too thick, resulting in excessive softness of the material or affecting the strength. The design of this layer aims to balance the elasticity and firmness of the composite material, enabling the luggage to have better anti-damage ability during use.

[0044] This design of thickness ratio ensures that the functions of each layer of the composite material can complement and cooperate with each other. The reinforcing fiber layer provides strong support, the functional response layer can make intelligent responses under changing external conditions, and the buffer support layer effectively absorbs and disperses external impact forces. This innovative design of layer distribution enables the composite material to achieve an optimal balance in terms of strength, flexibility, and impact resistance, meeting the technical objectives of the present invention in terms of intelligence and multi-function requirements.

[0045] Preferably, in step S2, the composite material preform is placed into the first mold cavity and heated to 120 - 180 °C, and the heating time is 60 - 120 seconds.

[0046] First of all, in this step, the composite material preform is heated to a temperature range of 120 - 180 °C. This temperature range is properly designed, which can not only effectively soften the resin matrix in the composite material to make it have sufficient fluidity for subsequent molding, but also avoid excessive temperature causing material degradation or over-softening. Heating to this temperature improves the adhesion of the resin matrix between the reinforcing fiber layer and the functional response layer, ensuring good bonding between each layer, thereby providing a stable foundation for subsequent injection molding.

[0047] The heating time is set to 60 - 120 seconds, aiming to ensure sufficient softening of the material while avoiding excessive heating time causing material over-aging or performance degradation. This time range ensures that the composite material is fully heated in the mold cavity, making it reach a suitable softening state during initial shaping, laying a good foundation for precise molding during the injection molding process. By reasonably controlling the heating time and temperature, the adaptability and stability of each layer of material can be effectively guaranteed, avoiding unnecessary energy waste, and at the same time ensuring the uniformity of the composite material.

[0048] The innovation of this step lies in that by precisely controlling the temperature and heating time, the composite material preform can achieve the best combination and shaping of the material when softening in the first mold cavity. A reasonable heating process not only optimizes the fluidity and processability of the resin matrix, but also promotes the molecular bonding and cross-linking reaction between different layers of materials through heat treatment of the material, creating superior conditions for subsequent injection molding. The thermal response differences of each layer of material during the heating process are also precisely controlled within an ideal range, thereby avoiding performance decline or interface peeling of the material caused by uneven heating or overheating.

[0049] Preferably, in step S3, the melting temperature of the thermoplastic material is 220 °C - 260 °C, the intensity of the magnetic field is 150 mT - 250 mT, and the temperature of the thermal excitation is 60 °C - 90 °C.

[0050] First, the melting temperature of the thermoplastic material is set between 220°C and 260°C. This temperature range is carefully designed based on the melting point and processing characteristics of the thermoplastic resin. By controlling the melting temperature of the thermoplastic material, it can ensure that the material flows fully in the mold cavity and combines with the surface of the composite preform, while avoiding decomposition or performance degradation of the material caused by excessive temperature. This temperature range can ensure that the thermoplastic material obtains ideal formability during the injection molding process and solidifies into a stable structure during the subsequent cooling process.

[0051] At the same time, the magnetic field strength applied during the injection molding process is set to 150 mT to 250 mT. This magnetic field strength can effectively regulate the arrangement and distribution of magnetic-responsive particles in the composite material, enabling the magnetic-responsive particles in the functional response layer to be arranged directionally when the thermoplastic material is injected. Through the action of the magnetic field, the magnetic-responsive particles can form a specific structural distribution in the thermoplastic material, enhancing the response ability of the material under specific external stimuli. The design of the magnetic field strength ensures that the particles can reach an ideal arrangement state during the molding process, while avoiding uneven material properties caused by too strong a magnetic field.

[0052] During the injection molding process, the thermal excitation temperature is set to 60°C to 90°C. The thermal excitation within this range helps to improve the fluidity of the material and promote the adaptive reaction of the shape memory polymer in the functional response layer. During the combination of the thermoplastic material and the composite preform, the thermal excitation activates the polymer segments in the functional response layer through appropriate temperature control, enabling the functional response layer to complete morphological changes or performance optimization under the action of thermal excitation. This temperature range not only ensures the activation of the functional response layer but also avoids material damage or uneven thermal response caused by excessive temperature.

[0053] The present invention, by reasonably setting the melting temperature, magnetic field strength, and thermal excitation temperature of the thermoplastic material, enables the material to fully exert the functions of each layer during the injection molding process. Especially during the directional arrangement of magnetic-responsive particles and the activation of shape memory polymer in the functional response layer, a synergistic effect is generated. The guiding effect of the magnetic field ensures that the arrangement directions of the magnetic-responsive particles are consistent, thereby enhancing the responsiveness of the material under the action of an external magnetic field. The temperature control of the thermal excitation ensures the effective activation of the functional response layer, enabling the composite material to undergo morphological changes under external thermal stimuli and further enhancing the adaptive performance of the material.

[0054] Preferably, in step S4, the steps of the cooling treatment include:

[0055] Circulating coolant at 10°C to 20°C into the cooling channels of the second mold cavity for a cooling time of 40 seconds to 90 seconds, and maintaining the pressure in the second mold cavity at 5 MPa to 8 MPa during the cooling period.

[0056] First, the temperature of the coolant is set to 10°C to 20°C. This temperature range ensures the efficiency of the cooling process and the forming stability of the material. A lower coolant temperature helps to quickly reduce the temperature in the mold cavity, enabling the thermoplastic material to solidify and form in a shorter time, thus ensuring the shape stability of the composite material after cooling. An excessively high coolant temperature may lead to an overly slow forming speed, affecting production efficiency, and may cause local overheating of the material in the mold, resulting in stress concentration or deformation.

[0057] Secondly, the cooling time is controlled between 40 seconds and 90 seconds. This time period can not only ensure the uniform solidification of the material during the cooling process but also prevent the mold from being overly cooled due to an excessively long cooling time, which may affect the material properties or processing efficiency. Within this cooling time range, the material can gradually cool down and fully solidify, ensuring that the formed composite material has good structural integrity and stability.

[0058] Meanwhile, during the cooling process, the pressure in the second mold cavity is maintained between 5 MPa and 8 MPa. Appropriate pressure can prevent deformation or bubble formation caused by shrinkage due to temperature drop during the cooling process. Keeping the pressure in the mold cavity within this range helps to improve the density and shape stability of the material during cooling, avoiding defects caused by uneven mold pressure or too rapid material shrinkage. This pressure control is one of the important innovations of the present invention. By optimizing the environment in the mold cavity during the cooling process, the quality of the final composite material can be further improved.

[0059] During the cooling process, by precisely controlling the coolant temperature, cooling time, and mold cavity pressure, the uniformity and stability of the composite material during cooling and solidification are ensured. The control of the coolant temperature can accelerate the solidification speed of the thermoplastic material and prevent overheating or overcooling phenomena, avoiding local stress concentration or shape instability; the setting of the cooling time ensures the uniform cooling of the material and the full solidification of each part; and by maintaining appropriate mold cavity pressure during the cooling process, it is possible to avoid cracking or deformation of the formed composite material due to excessive internal stress.

[0060] Preferably, in step S4, the composite material luggage case is taken out when the temperature of the second mold cavity wall drops by 50°C to 60°C.

[0061] First, the design of reducing the temperature of the second mold cavity wall to 50°C to 60°C is mainly to ensure that the composite material can maintain the required shape stability during demolding and will not have thermal stress or surface defects caused by too rapid temperature drop. This temperature range can not only ensure the complete solidification of the material in the mold cavity but also avoid local stress concentration or morphological distortion of the formed material due to too large a temperature difference. Appropriate temperature drop helps the rapid stability of the composite material after demolding, reducing defects on the surface or inside of the material and ensuring the forming quality of the luggage case.

[0062] Secondly, demolding in this temperature range can prevent material embrittlement or adhesion problems between the mold and the material caused by overcooling. Too fast cooling may cause the thermoplastic material to be too hard and difficult to demold, and may even cause cracks or deformation during demolding. By accurately controlling the drop in the temperature of the mold cavity wall and the speed, the present invention ensures that the temperature and morphology of the material are balanced during demolding, which helps to extend the service life of the luggage and improve production efficiency.

[0063] This step finely regulates the temperature gradient of the composite material during the cooling process by controlling the temperature drop range of the mold cavity wall, avoiding the internal stress problem caused by excessive temperature difference. Within this temperature range, the composite material can smoothly transition to the solidified state, reducing the negative impact of the thermal shrinkage effect and ensuring that the material does not undergo uneven deformation or cracks during the cooling process.

[0064] The present invention provides a composite material bag injection molding process, which has the following beneficial effects:

[0065] 1. The present invention adopts a unique formula and optimized ratio of the reinforcing fiber layer, the functional response layer and the buffer support layer, so that the composite material luggage has significantly improved its performance in all aspects. Through the reasonable matching of the carbon fiber and the thermoplastic resin matrix in the reinforcing fiber layer, and the precise configuration of the shape memory polymer and the magnetic response particles in the functional response layer, the present invention solves the problem of performance mismatch between different functional layers in the prior art, and effectively improves the mechanical strength, shape memory ability and impact resistance of the composite material.

[0066] 2. The present invention achieves precise adjustment of the performance of composite materials by precisely controlling the thermal excitation and magnetic field effects during the heating and injection molding of composite material preforms. Experimental verification shows that by controlling factors such as melting temperature, magnetic field strength and thermal excitation temperature, the shape memory effect of composite materials during processing can be significantly improved. Compared with the process in the prior art that does not fully consider the synergistic effect of thermal excitation and magnetic field, the present invention solves the problems of long shape recovery time and low recovery rate caused by improper temperature and magnetic field treatment.

[0067] 3. The present invention optimizes the thickness ratio between the layers of the composite material so that the material can maintain high thermal responsiveness and shape recovery under different working conditions. Through the reasonable matching of the reinforcing fiber layer, the functional response layer and the buffer support layer, the various properties of the composite material are fully utilized. Compared with the insufficient material performance caused by the unreasonable hierarchical structure in the prior art, the optimization scheme of the present invention solves the defect of such unbalanced performance and improves the overall stability and service life of the composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1This is the process flow chart of the present invention. Detailed implementation manners

[0069] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0070] Unless otherwise specified, the raw materials and reagents used in the following embodiments are all commercially available products or can be prepared by known methods.

[0071] Please refer to the attached Figure 1 ,

[0072] Example 1:

[0073] The preparation of the composite preform includes three layers: a reinforcing fiber layer, a functional response layer, and a buffer support layer. In the composition of the reinforcing fiber layer (by mass), carbon fiber accounts for 50 parts, the thermoplastic resin matrix is polyamide 6 accounting for 40 parts, the wear-resistant additive accounts for 6 parts, and the surface treatment agent accounts for 3 parts, forming a reinforcing fiber layer with a total thickness of 2.0 mm. The functional response layer (by mass) consists of 40 parts of shape memory polymer, 20 parts of magnetic response particles (particle size of 50 nm), 30 parts of elastic matrix, 3 parts of dispersant, and 2 parts of heat stabilizer, forming a functional response layer with a total thickness of 1.0 mm. The buffer support layer (by mass) is composed of 60 parts of thermoplastic elastomer, 10 parts of foaming agent, 10 parts of impact modifier, 5 parts of compatibilizer, and 2 parts of anti-aging agent, with a thickness of 1.0 mm.

[0074] The composite preform is heated to 160 °C in the first mold cavity and kept heated for 90 seconds to ensure that the resin matrix reaches the required softening state to provide suitable adhesiveness for subsequent injection molding. The heated preform is transferred to the second mold cavity and injected into the mold cavity at the melting temperature of the thermoplastic material of 220 °C. At the same time, a magnetic field strength of 200 mT and a thermal excitation temperature of 75 °C are applied to ensure the directional arrangement of the magnetic response particles and activate the shape memory polymer, thereby enhancing the responsiveness and self-adaptive characteristics of the composite material.

[0075] After the injection molding process is completed, it enters the cooling stage. By circulating coolant at 10 °C through the cooling channels of the second mold cavity, the cooling time is set to 75 seconds, and the mold cavity pressure is maintained at 6 MPa. During cooling, the temperature in the mold cavity gradually decreases, and when the temperature of the mold cavity wall drops to 55 °C, the composite material luggage case is taken out.

[0076] Example 2:

[0077] In the composition of the composite preform, the reinforcing fiber layer (by mass parts) uses 70 parts of carbon fiber and 30 parts of polyamide 6 resin matrix, and the proportions of wear-resistant additives and surface treatment agents are 10 parts and 5 parts respectively, with a total thickness of 3.0 mm. The functional response layer (by mass parts) consists of 60 parts of shape memory polymer, 30 parts of magnetic response particles (particle size of 100 nm), 40 parts of elastic matrix, 5 parts of dispersant, and 3 parts of heat stabilizer, with a thickness of 1.5 mm. The buffer support layer (by mass parts) has a ratio of 80 parts of thermoplastic elastomer, 15 parts of foaming agent, 20 parts of impact modifier, 8 parts of compatibilizer, and 3 parts of anti-aging agent, with a total thickness of 1.5 mm.

[0078] The composite preform is heated to 180 °C in the first mold cavity and kept heated for 120 seconds to ensure that the longer heating time fully softens the resin matrix of the composite material. The heated composite preform is transferred to the second mold cavity, and molten polypropylene is injected into the mold cavity at a molten temperature of 260 °C, with a magnetic field strength of 250 mT applied and a thermal excitation temperature set at 90 °C to activate the shape memory polymer and precisely control the arrangement of magnetic response particles.

[0079] During the cooling process, the coolant temperature is set at 20 °C, the cooling time is 90 seconds, and the mold cavity pressure is 8 MPa. When the mold cavity wall temperature drops to 60 °C, the formed composite material luggage case is taken out. This configuration ensures that the composite material has higher strength, rigidity, and intelligent response ability, and is suitable for more demanding usage environments.

[0080] Example 3:

[0081] The reinforcing fiber layer (by mass parts) uses 30 parts of carbon fiber and 50 parts of polypropylene resin matrix, and the proportions of wear-resistant additives and surface treatment agents are 2 parts and 1 part respectively, with a total thickness of 1.5 mm. The functional response layer (by mass parts) consists of 20 parts of shape memory polymer, 10 parts of magnetic response particles (particle size of 10 nm), 10 parts of elastic matrix, 1 part of dispersant, and 1 part of heat stabilizer, with a thickness of 0.75 mm. The buffer support layer (by mass parts) has a ratio of 40 parts of thermoplastic elastomer, 5 parts of foaming agent, 5 parts of impact modifier, 2 parts of compatibilizer, and 1 part of anti-aging agent, with a total thickness of 0.75 mm.

[0082] The composite preform is heated to 120 °C in the first mold cavity, and the heating time is 60 seconds. At this time, the resin matrix of the composite preform is moderately softened, ensuring good interlayer adhesion. During the injection molding process, a molten temperature of 220 °C is used, a magnetic field strength of 150 mT is applied, and the thermal excitation temperature is 60 °C to ensure the proper activation of the shape memory polymer and the orderly arrangement of magnetic response particles.

[0083] During the cooling stage, the coolant temperature is set at 10°C, the cooling time is 40 seconds, and the cavity pressure is maintained at 5 MPa. When the cavity wall temperature drops to 50°C, the composite material luggage case is taken out.

[0084] Comparative Example 1:

[0085] Compared with Example 1, the difference lies in that the carbon fiber in the reinforcing fiber layer is reduced to 30 parts, the thermoplastic resin matrix is increased to 50 parts, the ratio of wear-resistant additive to surface treatment agent is 2 parts and 1 part, and the total thickness is adjusted to 2.5 mm, and the rest are the same.

[0086] Comparative Example 2:

[0087] Compared with Example 1, the difference lies in that the shape memory polymer in the functional response layer is reduced to 30 parts, the magnetic response particles are reduced to 15 parts, the particle size is 80 nm, the elastic matrix is reduced to 25 parts, the heat-resistant stabilizer is reduced to 1 part, the total thickness is adjusted to 0.75 mm, and the rest are the same.

[0088] Comparative Example 3:

[0089] Compared with Example 1, the difference lies in that the thermoplastic elastomer in the buffer support layer is reduced to 50 parts, the foaming agent is reduced to 5 parts, the impact modifier is reduced to 5 parts, the compatibilizer and antioxidant are reduced to 3 parts and 2 parts respectively, the total thickness is adjusted to 1.25 mm, and the rest are the same.

[0090] Comparative Example 4:

[0091] Compared with Example 1, the difference lies in that the melting temperature of the molten thermoplastic material in step S3 is reduced to 230°C, the magnetic field strength is reduced to 150 mT, and the thermal excitation temperature is reduced to 65°C, and the rest are the same.

[0092] Comparative Example 5:

[0093] Compared with Example 1, the difference lies in that the heating temperature in step S2 is adjusted to 140°C and the heating time is shortened to 75 seconds, and the rest are the same.

[0094] Comparative Example 6:

[0095] Compared with Example 1, the difference lies in that the coolant temperature in step S4 is reduced to 12°C, the cooling time is reduced to 50 seconds, the cavity pressure is reduced to 5 MPa, and the composite material luggage case is taken out when the cavity wall temperature drops to 53°C, and the rest are the same.

[0096] Experiment 1:

[0097] Experimental steps:

[0098] Sample preparation:

[0099] Prepare composite material samples for Preparation Example 1 and Comparative Examples 1, 2, and 3. The size of each sample should be 20 cm × 5 cm × 2.0 mm.

[0100] Sample labeling:

[0101] Label each composite material sample as A (Preparation Example 1), B (Comparative Example 1), C (Comparative Example 2), and D (Comparative Example 3) to ensure the distinction of samples with different component ratios in the experiment.

[0102] Equipment preparation:

[0103] Use a tensile testing machine and ensure that the equipment has been adjusted for the holder and load cell according to the material specifications.

[0104] Conduct tensile tests:

[0105] Install each labeled composite material sample successively in the fixture of the testing machine to ensure that the material is completely fixed.

[0106] Start the tensile test and record the tensile strength (maximum tensile force) and elongation at break of each sample.

[0107] During the test, record the force-displacement curve and calculate the elastic modulus (obtained from the slope of the linear segment).

[0108] Data recording is shown in Table 1:

[0109] Conduct at least three repeated tests for each sample to ensure the reliability of the data.

[0110] Record the data of each test, including the tensile strength, elongation at break, and elastic modulus of the sample.

[0111] Table 1: Effects of different ratios of reinforcing fiber layers on the tensile strength, elongation at break, and elastic modulus of the composite material

[0112] Sample Number Tensile Strength (MPa) Elongation at Break (%) Modulus of Elasticity (GPa) A (Example 1) 142.6 3.5 12.3 B (Comparative Example 1) 138.4 4 11.8 C (Comparative Example 2) 125.7 3.8 11.5 D (Comparative Example 3) 110.2 3.2 10.9 A (Example 1) 146.3 3.7 12.5 B (Comparative Example 1) 139.8 3.9 11.9 C (Comparative Example 2) 122.5 3.6 11.3 D (Comparative Example 3) 108.7 3.1 10.7 A (Example 1) 141.2 3.6 12.1 B (Comparative Example 1) 137.2 4.1 11.7 C (Comparative Example 2) 127.3 3.9 11.6 D (Comparative Example 3) 112.5 3.3 11

[0113] The experimental results show that the carbon fiber content has a significant effect on the strength and rigidity of the composite material. The higher proportion of carbon fiber in Preparation Example 1 results in larger tensile strength and elastic modulus of the composite material, indicating that the reinforcing fiber layer can effectively improve the tensile strength and rigidity of the material. As the carbon fiber content decreases (Comparative Examples 1, 2, and 3), the strength and rigidity of the material gradually decline. Especially in Comparative Example 3, the material exhibits lower tensile strength and elastic modulus, demonstrating the key role of carbon fiber in enhancing mechanical properties.

[0114] The change in elongation at break reflects the ductility of the material. When the carbon fiber is reduced, the ductility is improved, which is related to the increase in the proportion of the resin matrix. However, this increase in ductility fails to effectively compensate for the effects of reduced strength and rigidity, especially for Example 3, whose low strength and low rigidity limit the practical application of its ductility advantage.

[0115] The decrease in elastic modulus further confirms the decisive role of carbon fiber in the rigidity of the material. The high carbon fiber ratio in Example 1 gives the material higher rigidity, while in Comparative Example 3, the carbon fiber content is minimal, resulting in a significant decrease in elastic modulus, indicating that the rigidity of the composite material is poor when subjected to external loads and its application performance is limited.

[0116] Experiment 2:

[0117] Sample preparation:

[0118] Prepare composite material samples of Example 1 and Comparative Examples 4, 5 and 6, each with a size of 20 cm×5 cm×2.0 mm, ensuring that the composition of the functional response layer in each sample is the same (i.e., the ratio of the shape memory polymer and the magnetic response particles is consistent with that in Example 1).

[0119] Sample marking:

[0120] Each sample was labeled E (Example 1), F (Comparative Example 4), J (Comparative Example 5), and K (Comparative Example 6) to ensure that the different experimental groups could be distinguished.

[0121] Equipment preparation:

[0122] Use thermal stress testers and magnetic field excitation devices to ensure that the equipment can regulate and control heating, cooling, thermal excitation temperature and magnetic field strength. To ensure accurate test conditions, install temperature sensors and magnetic field strength measuring instruments.

[0123] Heating and thermal stimulation treatment:

[0124] The samples were placed in a thermal stress tester and processed according to the following steps, keeping the heating, thermal excitation and magnetic field intensity conditions consistent for each experimental group:

[0125] Heat to 160°C and hold for 90 seconds.

[0126] The magnetic field strength was set to 200 mTesla.

[0127] The thermal excitation temperature was set at 75°C to ensure that each group of samples underwent the same thermal excitation treatment.

[0128] Recording shape memory changes:

[0129] After heating and exciting each group of samples, they were quickly cooled to room temperature, and the shape recovery of each sample under different excitation conditions was observed and recorded. The shape recovery rate and recovery time (the time from applying the stimulus to reaching the maximum recovery) were recorded.

[0130] Data recording (see Table 2) and analysis:

[0131] At least three repeated experiments were carried out on each group of samples to ensure the reliability of the data.

[0132] Data such as the shape recovery rate and recovery time of each experiment were recorded. The experimental data included key parameters such as temperature, recovery time, and shape memory rate.

[0133] Table 2: Effects of different excitation conditions on the shape recovery rate, recovery time, and magnetic field strength of the composite material

[0134]

[0135] In this experiment, the thermal response performance of the functional response layer of the composite material was systematically tested to evaluate the effects of different treatment conditions on the shape memory behavior of the material. The heating, magnetic field strength, and thermal excitation conditions of all experimental groups (Example 1, Comparative Example 4, Comparative Example 5, and Comparative Example 6) were kept consistent, ensuring the comparability of the data and the accuracy of the experiment. Through the analysis of the experimental data, the significant effects of heating temperature, magnetic field strength, and cooling conditions on the properties of the composite material were revealed, and these results were closely related to the molecular structure and shape memory mechanism of the material.

[0136] First of all, all samples in the experiment were heat-treated at 160 °C, and this condition played a key role in the phase change of the shape memory polymer. The phase change temperature of the shape memory polymer is usually closely related to its glass transition temperature. The experimental results showed that after heating to this temperature, the material could achieve effective shape recovery. Among all experimental groups, Example 1 (E) had a relatively high shape recovery rate, indicating that it could achieve a better shape memory effect within a shorter recovery time. The condition of a magnetic field strength of 200 mT also showed that the distribution of magnetic response particles in the polymer matrix had an important effect on the thermal response ability of the material. The action of the magnetic field improved the shape recovery ability of the material by inducing the rearrangement of magnetic particles in the polymer.

[0137] In terms of thermal stimulation, a thermal stimulation temperature of 75 °C plays an important role in the recovery of the material, ensuring the flexibility of the polymer molecular chains and thus promoting the shape recovery of the material. This thermal stimulation temperature showed similar effects in different experimental groups. Among them, the sample of Example 1 showed excellent performance in terms of shape recovery rate and recovery time under the combined action of temperature and magnetic field. On the contrary, although Comparative Example 4 had the same treatment conditions as Example 1, its shape recovery rate was relatively low, which may be due to the different component ratios of the material and the dispersion of the magnetic response particles. By comparing the experimental results, it can be speculated that optimizing the functional response layer of the composite material to make the ratio of polymer to magnetic particles more reasonable will help improve the shape memory effect of the material.

[0138] Generally speaking, the results of this experiment clearly show that the shape memory performance of the composite material is not only affected by the heating temperature and thermal stimulation conditions, but also significantly affected by the magnetic field strength and the internal structure of the material. Under the combined action of these factors, Example 1 showed relatively ideal shape recovery performance. Based on this mechanism, future material design can further improve the shape memory ability and its thermal response performance of the composite material by optimizing the ratio of polymer to magnetic response particles and precisely controlling the treatment process.

[0139] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A composite material luggage injection molding process, characterized in that, It includes the following steps: S1. Provide a composite material preform, which sequentially includes a reinforcing fiber layer, a functional response layer, and a buffer support layer; S2. Place the composite material preform into a first mold cavity for heat treatment to soften it and preliminarily shape it in the mold cavity; S3. Transfer the heat-treated composite preform to a second mold cavity, inject molten thermoplastic material into the second mold cavity, and simultaneously apply a magnetic field and a thermal excitation during the injection molding process; S4. After the injection molding process is completed, perform a cooling treatment on the second mold cavity, and take out the molded composite material luggage from the second mold cavity.

2. The injection molding process of a composite material luggage case according to claim 1, characterized in that, In the step S1, the reinforcing fiber layer, by mass, includes 30-70 parts of carbon fiber, 20-50 parts of a thermoplastic resin matrix, 2-10 parts of an abrasion-resistant additive, and 1-5 parts of a surface treatment agent; The thermoplastic resin matrix is one of polyamide 6, polypropylene, or polyether ether ketone.

3. A composite material luggage injection molding process according to claim 1, characterized in that, In the step S1, the functional response layer, by mass, includes 20-60 parts of a shape memory polymer, 10-30 parts of magnetic response particles, 10-40 parts of an elastic matrix, 1-5 parts of a dispersant, and 1-3 parts of a heat stabilizer; The magnetic response particles have a particle size of 10-100 nanometers and are coated with a silane-based dispersion coating on the surface.

4. A composite material luggage injection molding process according to claim 1, characterized in that, In the step S1, the buffer support layer, by mass, includes 40-80 parts of a thermoplastic elastomer, 5-15 parts of a foaming agent, 5-20 parts of an impact-resistant modifier, 2-8 parts of a compatibilizer, and 1-3 parts of an anti-aging agent.

5. A composite material luggage injection molding process according to claim 1, characterized in that, The thickness ratio of the reinforcing fiber layer, the functional response layer, and the buffer support layer is 2:1:1 to 4:3:2, and the total thickness is 1.5-3.0 millimeters.

6. A composite material luggage injection molding process according to claim 1, characterized in that, In the step S2, the composite material preform is placed into the first mold cavity and heated to 120-180 °C, and the heating time is 60-120 seconds.

7. A composite material luggage injection molding process according to claim 1, characterized in that, In the step S3, the melting temperature of the thermoplastic material is 220 °C to 260 °C, the intensity of the magnetic field is 150 mT to 250 mT, and the temperature of the thermal excitation is 60 °C to 90 °C.

8. A composite material luggage injection molding process according to claim 1, characterized in that, In the step S4, the steps of the cooling treatment include: Circulatingly input a coolant at 10 °C to 20 °C into the cooling channels of the second mold cavity, the cooling time is 40 seconds to 90 seconds, and the pressure in the second mold cavity is maintained at 5 MPa to 8 MPa during the cooling period.

9. A composite material luggage injection molding process according to claim 1, characterized in that, In the step S4, the composite material luggage is taken out when the temperature of the second mold cavity wall drops by 50 °C to 60 °C.

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