Honeycomb core racket with foaming material and processing technology of honeycomb core racket

Abstract

The invention relates to the technical field of racket preparation, and discloses a honeycomb core racket with a foaming material, which comprises a honeycomb core sheet used for forming an internal support structure of the racket, the side length of the honeycomb core sheet is 3-10mm, and the thickness of the honeycomb core sheet is 8-20mm; the foaming elastic material layer is attached to at least one side of the honeycomb chip; the outer surface of the foaming elastic material layer is covered with the fiber reinforcement layer, and the fiber reinforcement layer is made of one of carbon fibers, glass fibers or Kevlar materials; the honeycomb chip, the foaming elastic material layer and the fiber reinforcing layer are laminated to form a composite board; the composite board is cut to form a racket body and is provided with a handle connecting part. Under the condition of bearing repeated striking load, the high-rigidity shock absorber has high bending rigidity, excellent shock attenuation capacity and good fatigue tolerance performance. Compared with an existing racket with a single structure or separated interlayer functions, the racket has the advantages that the interlayer stripping and microcrack propagation risks can be remarkably reduced, the service life of the structure is prolonged, and the control stability and comfort in the ball hitting process are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of racket preparation, and specifically to a honeycomb core racket with foaming material and its processing technology. Background Art

[0002] Currently, among ball sports equipment, racket products are widely used in projects such as badminton, tennis, and squash. Their structural performance has a direct impact on aspects such as hitting control, use feel, and service life. To improve the strength, rigidity, and lightweight performance of rackets, a multi-layer composite structure is usually adopted, including the combination of fiber reinforcement materials, core materials, and resin layers. At the same time, to reduce the vibration transmitted to the hand during hitting and improve the comfort of use, some products introduce a buffer layer or energy-absorbing material in the structure.

[0003] In the prior art, a known structural method is to use carbon fiber or glass fiber combined with a honeycomb core material to form a racket frame structure. This type of structure provides basic strength and rigidity through the reinforcement layer, and the honeycomb core realizes weight control. In some structures, materials such as rubber and foam are added in the holding area or racket panel to absorb hitting vibrations and relieve impacts. However, in this type of structure, there is a lack of synergy between the reinforcement layer, core material, and buffer material. The functions of each layer are relatively independent, and there is a problem of uneven response in the overall structure under the stress state.

[0004] The following problems still remain unsolved in the prior art: During the long-term repeated hitting and use of the racket, it is easy to cause structural fatigue damage due to the accumulation of interlayer stress, manifested as fiber layer peeling, honeycomb core deformation, or interface debonding, resulting in a decrease in rigidity and deterioration of use performance, and unable to balance the comprehensive requirements of strength, comfort, and durability. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a honeycomb core racket with foaming material and its processing technology, which solves the problems of easy structural fatigue damage, insufficient vibration control, and performance decline during the repeated use of rackets in the prior art.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A honeycomb core racket with foaming material, comprising:

[0007] A honeycomb chip, used to form the internal support structure of the racket, with a side length of 3 - 10 mm and a thickness of 8 - 20 mm;

[0008] A foaming elastic material layer, adhesively disposed on at least one side of the honeycomb chip;

[0009] A fiber reinforcement layer, covering the outer surface of the foaming elastic material layer, and the fiber reinforcement layer is one of carbon fiber, glass fiber, or Kevlar material;

[0010] The honeycomb chip, the foamed elastic material layer and the fiber reinforced layer are laminated to form a composite board;

[0011] The composite board is cut to form a racket body, and a handle connection part is provided.

[0012] Preferably, the honeycomb chip is an aluminum honeycomb core, an aramid paper honeycomb core or a polymer honeycomb core.

[0013] Preferably, the foamed elastic material layer is a thermoplastic polyurethane material.

[0014] Preferably, the fiber reinforced layer is attached to the foamed elastic material layer by hot pressing or cold pressing.

[0015] Preferably, a protective edge structure is provided at the edge of the racket, and the handle is fixed to the racket body by gluing or mechanical connection.

[0016] A processing technology for a honeycomb core racket with foamed material includes the following steps:

[0017] S1. Provide a honeycomb chip;

[0018] S2. Attach the foamed elastic material layer to at least one side of the honeycomb chip;

[0019] S3. Set a fiber reinforced layer outside the foamed elastic material layer, and the fiber reinforced layer is one of carbon fiber, glass fiber or Kevlar material;

[0020] S4. After laminating the honeycomb chip, the foamed elastic material layer and the fiber reinforced layer, perform a forming process, and the forming process is any of the following methods:

[0021] Thermoforming: Perform die pressing through a hot pressing die at 180°C - 220°C and a pressure of 60 tons - 100 tons;

[0022] Cold forming: At room temperature, attach by pressing, the pressure is 20 - 50 tons, and form a racket structure through cutting;

[0023] Combined hot and cold forming: First, perform thermoforming on part of the structure, and then perform cold pressing and attachment;

[0024] S5. Cut, trim the formed structure, and install the handle assembly

[0025] Preferably, the foamed elastic material layer is formed by a supercritical fluid foaming process.

[0026] Preferably, a hot melt adhesive bonding layer or an epoxy resin glue layer is provided between the foamed elastic material layer and the fiber reinforced layer.

[0027] Preferably, in the hot-cold combined molding method, the honeycomb chip and the first fiber reinforced layer are firstly subjected to hot pressing, and then the foamed elastic material layer and the second fiber reinforced layer are bonded together by cold pressing.

[0028] Preferably, an edge strip is provided on the outer edge of the molding structure, and a handle, a marking layer and an anti-slip tape are installed after molding.

[0029] The present invention provides a honeycomb core racket with foaming material and a processing technology thereof, which has the following beneficial effects:

[0030] 1. The present invention adopts a multi-layer composite structure design of a carbon fiber reinforcement layer combined with a honeycomb core and a TPU buffer layer, achieving the technical effect of significantly improving the impact resistance and rigidity stability of the racket while maintaining the structural strength. Compared with the simple structure of only using a single layer of reinforcement material or no buffer layer in the prior art, it solves the reliability problems of easy cracking of the structure, insufficient rigidity, and easy debonding after repeated stress.

[0031] 2. The present invention adopts a double-layer TPU foam material embedded between functional layers to achieve excellent vibration attenuation and feel optimization capabilities. Traditional solutions often ignore the dispersion path of vibration energy, resulting in strong impact on the hand. This technology effectively improves the problems of high-frequency vibration that cannot be buffered, stiff feedback from hitting the ball, and poor user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the racket structure of the present invention;

[0033] Figure 2 It is a schematic diagram of the method flow of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Embodiment 1:

[0036] Please refer to the attached Figure 1-2 The embodiment of the present invention provides a honeycomb core racket with foaming material and a processing technology thereof, including:

[0037] First, an aluminum honeycomb core material is selected. Its size is precisely cut to meet the specifications required for the racket design, with a thickness of 8 mm, and precise cutting is carried out using laser cutting technology. The structure of the honeycomb core is a hexagonal pore arrangement, which can provide an excellent lightweight strength ratio and effectively disperse impact stress during movement. The design of the honeycomb structure enables it to maintain a stable supporting effect under load and avoid racket deformation caused by concentrated external forces.

[0038] This honeycomb core material plays a key role in the anti-bending, anti-impact, and anti-fatigue performance of the racket, ensuring that the racket is not easily damaged during use.

[0039] The foam material layer is a supercritical foam TPU (thermoplastic polyurethane) material. The TPU material made by supercritical fluid foaming technology has a uniform and delicate microporous structure, which is superior to traditional foam materials, greatly improving the elasticity and comfort of the material, and performing outstandingly in aspects such as shock absorption effect, energy absorption, and stability. The thickness of this material is 2 mm, and the density is 0.18 g / cm 3 , with high compressive capacity and elastic recovery, suitable for vibration buffering and comfort improvement of the racket panel.

[0040] During the manufacturing process, the foam TPU material layer will be evenly coated on both the front and back sides of the honeycomb core by means of a hot melt adhesive film. This adhesive film is a hot melt adhesive with high bonding strength, which can ensure a stable bond between the foam material and the honeycomb core. After the adhesive film is coated, the honeycomb core and the foam layer are placed on a specific thermoforming platform, and by applying a certain pressure and temperature, the two are firmly bonded together.

[0041] Outside the foam layer, a layer of carbon fiber prepreg will be laid, with a thickness of 0.25 mm. The function of this layer of carbon fiber cloth is to enhance the rigidity of the racket panel and improve the power transmission and anti-torsion strength of the racket. The surface of the prepreg is coated with resin to facilitate the subsequent curing process.

[0042] The laying of the carbon fiber cloth is completed by manual operation to ensure that the carbon fiber cloth is closely fitted with the foam layer and the honeycomb core. After laying, the composite structure is placed in a thermoforming platform and hot-pressed under the conditions of a temperature of 200 °C and a pressure of 80 tons. The pressure holding time is set to 8 minutes. The hot-pressing process cures the resin, and the carbon fiber reinforcement layer, the foam material layer, and the honeycomb core layer form a firm composite integral structure.

[0043] During this process, thermoforming not only promotes the curing of the resin but also enables the carbon fiber reinforcement layer to be evenly combined with the foam layer and the honeycomb core, further enhancing the stability and durability of the racket.

[0044] The composite material after hot pressing will be taken out and cooled naturally. The cooling time is about 30 minutes. After cooling, the overall structure of the racket panel has been formed, and good mechanical properties and stability have been maintained.

[0045] Next, a numerical control cutting device is used to finely trim the racket panel to ensure that its edges and shape meet the design requirements. This process includes removing excess materials, trimming the outer contour of the racket, and strengthening the racket according to predetermined parameters.

[0046] In addition, drilling and cutting processes will also be carried out to prepare for the installation of the subsequent handle assembly and the fixation of other accessories. The hole positions on the racket edge and the central area are precisely calibrated and cut to ensure uniform weight distribution of the racket.

[0047] The handle is installed in a dual manner using epoxy resin glue and mechanical fixation. First, the handle is fixed to the tail of the racket with resin glue, and then screws or rivets are used for reinforcement. Different materials can be selected for the handle part according to user needs to increase comfort or enhance control.

[0048] After the handle is installed, the surface of the racket will be silk-screened with the company logo, racket model, and other necessary identification marks to enhance the recognition and aesthetics of the product.

[0049] Finally, the overall assembly of the racket is completed, and through quality inspection and trial play verification, it is ensured that the performance meets the expected requirements, ensuring that each racket has high-intensity impact resistance, excellent shock absorption effect, and comfortable use experience.

[0050] Example 2:

[0051] The embodiment of the present invention provides a honeycomb core racket with foaming material and its processing technology, including:

[0052] In this embodiment, the racket is manufactured using a cold forming process. Compared with the hot forming process, the cold forming process has the advantages of low energy consumption, simple process, strong adaptability, etc., is suitable for mass production, and can effectively control the manufacturing cost and product quality.

[0053] First, a polypropylene composite honeycomb core is selected, and its thickness is set to 8 mm, providing good mechanical support and bending strength. This honeycomb core material has excellent structural stability and can effectively disperse the stress generated during hitting, thereby improving the anti-deformation ability of the racket.

[0054] During the material preparation process, the honeycomb core will be precisely cut into the size that meets the design requirements through laser cutting technology, and it is ensured that each hexagonal pore is evenly distributed. This can ensure the structural uniformity of the honeycomb core, optimize the lightweight design of the racket, and at the same time ensure its overall strength.

[0055] The foaming material layer is made of low-density closed-cell polyurethane foam with a thickness of 2 mm and a density of 0.16 g / cm 3 , which has excellent shock absorption performance and elastic recovery ability. This foaming material plays a role in energy absorption and buffering in the manufacture of the racket, effectively reducing the vibration transmitted to the hand during hitting.

[0056] During the manufacturing process, first, the foaming material is cut into required sizes to ensure it covers the entire surface of the honeycomb core. Subsequently, a high-viscosity structural adhesive is used to bond the foaming material to both the front and back sides of the honeycomb core. The structural adhesive is evenly applied by hand on the contact surfaces of the foaming material and the honeycomb core to ensure a tight bond between them.

[0057] Subsequently, the foaming material and the honeycomb core are placed in a cold forming platform, and the two are pressed together through a cold pressing process. A pressure of 4 tons is applied and maintained for 30 minutes to ensure sufficient curing and bonding at the interface between the foaming material and the honeycomb core. During the cold pressing process, the glue cures at room temperature, making the bond between the foaming layer and the honeycomb core stable and not prone to structural deformation due to high temperature.

[0058] A fiberglass cloth with a thickness of 0.25 mm is laid outside the foaming layer. The fiberglass cloth can provide additional strength to the racket, making the racket have higher rigidity and impact resistance during hitting.

[0059] The laying of the fiberglass cloth is carried out manually to ensure it fits tightly with the foaming layer. When laying the fiberglass cloth, it must be ensured that the cloth layer completely covers the foaming material and maintains a certain degree of uniformity. This process can further improve the anti-torsion ability and bending strength of the racket.

[0060] After laying, cold pressing is carried out through a room-temperature pressing device to firmly bond the fiberglass layer and the foaming layer. A pressure of 4 tons is applied and maintained for 30 minutes to form a strong bond between the fiber layer and the foaming layer. At this time, the overall strength of the composite structure is improved, further enhancing the performance of the racket during use.

[0061] The composite material after cold pressing and forming will be taken out and cooled naturally for about 1 hour. The cooling process can make the glue in the structure completely cure, ensuring the structural stability of each layer of the racket.

[0062] The cooled composite structure will be trimmed on a numerical control cutting device to precisely cut out the outer contour of the racket and trim the edges according to the design requirements. This step includes removing excess materials to ensure that the racket's shape conforms to the predetermined dimensions and carefully processing the racket edges to make the overall appearance of the racket smoother and more even.

[0063] The trimmed racket faceplate will enter the handle installation stage. First, the handle assembly is fixed to the tail of the racket with epoxy resin glue. The resin glue can not only effectively fix the handle, but also provide additional bonding strength to ensure that the handle is not easily detached during the use of the racket.

[0064] Then, rivets or screws are used for further mechanical fixation of the handle to enhance its stability. After the handle installation is completed, the overall structure of the racket has been formed.

[0065] Subsequently, the racket surface will be printed with LOGO, numbers and other markings through the silk-screen process to enhance the brand recognition and aesthetics of the racket.

[0066] The assembled rackets will undergo a series of quality inspections and performance verifications, including but not limited to: anti-bending test, vibration transfer test, strength and durability test, etc. During the test process, ensure that each racket meets the product design standards in terms of structure, function and appearance, and can meet the requirements of high-intensity use.

[0067] Example 3:

[0068] The embodiment of the present invention provides a honeycomb core racket with foaming material and its processing technology, including:

[0069] This embodiment adopts a combination of hot and cold processes to improve the performance and stability of the racket. This process combines thermoforming and cold forming technologies, and optimizes the structure and comfort of the racket by reasonably selecting the use and non-use of TPU foaming material. The specific manufacturing steps are as follows:

[0070] First, an aluminum honeycomb core is selected as the inner core of the racket. The honeycomb core has an excellent strength-to-weight ratio, can effectively provide the anti-bending and anti-deformation capabilities of the racket, and ensure the stability of the racket during strong hitting.

[0071] The honeycomb core material is cut into dimensions that meet the design requirements through precision laser cutting. To ensure the uniform and stable structure of the honeycomb core, the laser cutting process is strictly controlled to avoid unnecessary structural damage during the cutting of the core material.

[0072] Next, first a layer of carbon fiber cloth is adhered to the surface of the honeycomb chip. The selection standard of the carbon fiber cloth is 200g / m 2 , which has high strength and rigidity. The carbon fiber layer will be closely adhered to both sides of the honeycomb core to ensure the strength of its overall structure.

[0073] After the carbon fiber layer is bonded to the honeycomb core, the two layers of materials will be formed through a thermoforming process. In the thermoforming process, the honeycomb core and the carbon fiber layer are placed together on the thermoforming table. Through the action of high temperature and high pressure, it is ensured that the carbon fiber layer is firmly bonded to the honeycomb core, forming a stable composite structure.

[0074] The temperature during the thermoforming process is controlled at about 160 °C, the pressure is 70 tons, and the pressure holding time is 10 minutes, ensuring that the resin of the carbon fiber cloth is fully cured and enabling the honeycomb core and the carbon fiber layer to be tightly combined. This process makes the structure of the racket stable and capable of providing excellent strength and rigidity.

[0075] TPU foam material is added to the middle layer of the racket (i.e., on the carbon fiber layer), and this layer of material plays a role in shock absorption, buffering, and comfort. Whether to use TPU foam material can be selected according to different requirements and usage scenarios.

[0076] If TPU foam material is used, the foam layer is covered on the surface of the carbon fiber layer with a thickness of 2 mm. TPU foam material has good elasticity and shock absorption performance, which can effectively reduce the vibration transmitted to the hand during hitting and improve comfort. This foam material is bonded to the carbon fiber layer through thermoforming technology to fix it on the carbon fiber layer.

[0077] If the TPU foam layer is not used, this step is directly skipped and the next stage is entered.

[0078] If the TPU foam material layer is selected, then the cold forming process is used to cure the structure. The material with the previously added TPU foam layer and carbon fiber layer is placed in the cold forming table for curing treatment. The key to the cold forming process is to pressurize at room temperature to further cure and stabilize the material.

[0079] During this process, the combination of the TPU foam layer and the carbon fiber layer becomes closer. At the same time, the microporous structure of the foam layer remains stable, which can effectively improve the comfort and vibration absorption ability of the racket. This process also ensures the firm combination between the foam material and the carbon fiber layer, avoiding the performance decline of the racket caused by the loosening or delamination between the materials.

[0080] The pressure of the cold forming table is controlled at 50 tons, and the curing time is 30 minutes. The temperature of the cold forming process usually remains at room temperature, but through the action of high pressure, the bonding degree of each layer of material is ensured to reach the best state.

[0081] After the cold forming is completed, the composite material will be taken out and placed on the cooling table for natural cooling. The cooling time is about 1 hour. During the cooling process, the combination of the TPU foam layer and the carbon fiber layer is further stabilized, ensuring that the material structure does not undergo any deformation.

[0082] After cooling, the racket faceplate will be trimmed by a numerically controlled cutting device to ensure that the shape of the racket meets the design requirements. During the cutting process, excess material is removed and the edges of the racket are trimmed to make the racket surface smooth and flat.

[0083] The handle part of the racket is fixed to the tail of the racket with epoxy resin glue. The resin glue has extremely strong adhesiveness, which can ensure that the handle is firmly installed at the end of the racket.

[0084] After the handle is installed, the surface of the racket will undergo a silk-screening process to print the brand logo, model, and other relevant information. After printing, a final quality inspection is carried out, including vibration testing, strength testing, etc., to ensure that the performance of each racket meets the standards.

[0085] Comparative Example 1:

[0086] Compared with Example 3, the difference is that TPU foam material is not used, and the rest of the structure and process remain the same.

[0087] In Example 3, the TPU foam material is used as the key intermediate buffer layer and surface shock-absorbing layer. On the one hand, it is sandwiched between the honeycomb core and carbon fiber for energy absorption. On the other hand, another layer is laminated during the cold forming stage to enhance the comfort and elasticity of the racket. The role of TPU is to absorb high-frequency vibrations during the hitting process and reduce the recoil impact on the user's wrist and elbow.

[0088] In this comparative example, all TPU foam layers are removed, there is no elastic medium filling between the honeycomb core and the carbon fiber cloth, and the forming process is hot pressing and bonding carbon fiber and honeycomb core, and cold forming and secondary curing (but without the TPU layer).

[0089] Difference:

[0090] Material reduction: from a three-layer structure (carbon fiber + TPU + honeycomb core) to a two-layer structure (carbon fiber + honeycomb core);

[0091] Process simplification: TPU no longer participates in the pressing during the cold forming stage, reducing material preparation and bonding steps. The structural rigidity is improved, but the buffer adjustment ability is lost.

[0092] Comparative Example 2:

[0093] Compared with Example 1, the difference is that the carbon fiber reinforcement layer is replaced with a fiberglass cloth, and the rest of the structure, hot pressing process parameters, and material thickness remain the same.

[0094] In Example 1, the outer layer of the racket uses carbon fiber cloth (200g / m 2 ) as the main reinforcement material, and is compounded with the honeycomb core and TPU foam material through a thermoforming process to form a high-strength and high-rigidity faceplate.

[0095] In this comparative example, the carbon fiber cloth is replaced by glass fiber cloth (same thickness and weaving density). As a reinforcing material, glass fiber is significantly lower than carbon fiber in terms of strength, modulus, impact resistance, etc., but has lower cost and is easy to process.

[0096] the difference:

[0097] Material change: carbon fiber becomes glass fiber (same laying direction and thickness);

[0098] Thermoforming parameters remain unchanged: temperature 200°C, pressure 80 tons, holding pressure 8 minutes;

[0099] The structural appearance and thickness after molding are consistent, but the mechanical properties are essentially different

[0100] Comparative Example 3:

[0101] Compared with Example 2, the difference is that the carbon fiber reinforcement layer and the TPU foaming layer are removed, only the honeycomb core and the epoxy resin are retained, and the cold forming method is used for compression molding, and the other parameters are the same.

[0102] Example 2 adopts a multi-layer composite structure: the honeycomb core is the middle layer, and the inner and outer sides are respectively adhered with TPU foam material and reinforcing fiber (carbon fiber or glass fiber), which are composited and shaped by cold pressing equipment at normal temperature to ensure the structural strength and shock absorption performance of the racket.

[0103] This comparative example has a very simple structure, in which the surface reinforcing fibers and the foamed buffer layer are completely removed, and only a honeycomb core and a double-sided epoxy resin coating are used. It is solidified and formed through a cold pressing process, has no reinforcement layer or elastic layer, and completely relies on the support force of the honeycomb core.

[0104] Difference: Material reduction: composite structure becomes single-layer core material + epoxy adhesive bonding

[0105] No pre-impregnated fiber, no foamed energy-absorbing layer

[0106] The thickness after molding is relatively thin, the panel rigidity is seriously insufficient, and the overall structure is similar to a hollow bracket.

[0107] Experimental Example 1:

[0108] Purpose of the experiment: This experiment aims to evaluate the effects of different reinforcement materials (such as carbon fiber, glass fiber or no reinforcement) in the racket structure on the overall bending rigidity and impact resistance through standard mechanical tests, and to clarify the mechanism of the effect of material differences on the mechanical properties of the racket.

[0109] Experimental sample preparation:

[0110] A1: carbon fiber + honeycomb core + TPU, corresponding to Example 1;

[0111] A2: Glass fiber + honeycomb core + TPU; corresponding to proportion 2;

[0112] A3: Honeycomb core + epoxy (unreinforced); corresponding to Comparative Example 3.

[0113] For each group, 3 samples were prepared, and the dimensions were uniformly cut to 300 mm × 50 mm × finished product thickness.

[0114] Experimental equipment and parameters:

[0115] Three-point bending tester (automatically loaded, with displacement sensor);

[0116] Span between supports: 200 mm;

[0117] Loading speed: 5 mm / min;

[0118] Maximum force value: 1000 N;

[0119] Drop hammer impact test device (with impact recording system)

[0120] Punch mass: 5 kg;

[0121] Impact height: 50 cm;

[0122] Observe the damage and record the force value / damage energy;

[0123] The experimental steps are as follows:

[0124] 1. Three-point bending test

[0125] Place the sample horizontally on the supports, clamp it, and adjust the initial state;

[0126] Start the loading program and record the load-displacement curve;

[0127] Obtain the maximum deflection, fracture point, flexural modulus, etc.;

[0128] Each sample was tested once, and after repeating 3 samples, the average value and dispersion were taken.

[0129] 2. Impact strength test

[0130] Fix the sample on the impact platform;

[0131] Set the drop hammer height and weight, and release the punch;

[0132] Record the peak force value after impact, and whether there is penetration / crack / delamination;

[0133] Take pictures and observe the macroscopic structure changes and make records.

[0134] According to the above experimental steps, the experimental data were obtained and recorded in Table 1. The content of Table 1 is as follows:

[0135] Table 1. Test Results of Flexural and Impact Resistance Properties of Racket Samples with Different Structures

[0136]

[0137]

[0138] From the perspective of material mechanics, carbon fiber cloth has a higher Young's modulus and fracture strength, and it bears the main flexural load in the racket structure. In Example 1, carbon fiber is used as the surface layer reinforcement material, showing excellent rigidity and load-bearing capacity in the three-point bending test, manifested as a lower maximum deflection and a higher flexural modulus. In contrast, in Comparative Example 2, glass fiber is used to replace carbon fiber. Due to the lower modulus of glass fiber, it shows a more obvious flexure trend during force deformation, and the decrease in its rigidity directly affects the stability and control accuracy during the hitting process. In Comparative Example 3, the reinforcement layer is completely missing, and only the thin-wall structure of the honeycomb core body is relied on to bear the load, resulting in crushing, bulging or cracking under relatively low stress, and it cannot meet the basic structural rigidity requirements.

[0139] In terms of impact response, the distribution of the reinforcement material and the quality of the interface bonding determine the racket's resistance to instantaneous loads. Under the action of high stress in a short time, the carbon fiber composite layer can quickly disperse the load to the entire panel area, avoiding local stress concentration, so it shows a higher maximum bearing capacity and no obvious damage in the impact test. Although the glass fiber panel has a certain diffusion ability, its elastic modulus is relatively low, and local buckling or fiber fracture is likely to occur, resulting in local depression or bulging. For the honeycomb core structure lacking any reinforcement layer, an effective force diffusion path cannot be formed, causing the impact energy to be directly concentrated, and the honeycomb core is easily flattened and delaminated, ultimately resulting in large-area failure.

[0140] From the perspective of the mechanism of the overall structure, the mechanical properties of the composite structure racket depend on the collaborative work between multiple layers of materials. The carbon fiber layer provides an external support framework, the TPU foam layer undertakes energy absorption, and the honeycomb core provides a lightweight support skeleton. In the example, this structure realizes the coupling of rigidity and buffering, endowing the racket with the dual characteristics of high strength and high toughness. In the comparative examples, especially in Comparative Example 3, after the structure is simplified, the functions of each layer are missing, the force conduction path is interrupted, and the mechanical response shows local damage of a single material, losing the synergistic effect of the composite material system. This further proves the irreplaceability of the reinforcement material in the racket structure design.

[0141] Experimental Example 1:

[0142] Experimental Purpose: To evaluate the improvement effect of the TPU foam material on the absorption of hitting vibration and the comfort of use in the racket structure. Measure the vibration response through an acceleration sensor, and combine the subjective feedback of real users to comprehensively judge the performance differences of different structural designs in actual operation.

[0143] Sample preparation:

[0144] B1: Double - layer TPU foam structure, corresponding to Example 3;

[0145] B2: Without TPU foam, only honeycomb core + carbon fiber layer, corresponding to Comparative Example 1;

[0146] 1. Acceleration test

[0147] Equipment: MEMS high - sensitivity three - axis acceleration sensor

[0148] Installation location: Racket handle part (near the gripping area)

[0149] Sampling frequency: 10 kHz

[0150] Hitting method: Standard hitting with a fixed - force mechanical pendulum (ball speed about 80 km / h)

[0151] 2. Subjective scoring system

[0152] Evaluators: 10 medium - to - high - level hitters;

[0153] Hitting venue: Standard tennis wall;

[0154] After each tester uses each sample to hit 30 times, score the following items:

[0155] Shock absorption feeling (1 - 10 points);

[0156] Comfort of hitting feedback (1 - 10 points);

[0157] Hand numbness feeling due to shock (1 - 10 points, the higher the score, the more serious);

[0158] The experimental steps are as follows:

[0159] 1. Acceleration vibration test process

[0160] Fix the sample in the test fixture and paste the sensor at the handle position;

[0161] Start the pendulum mechanism and conduct standard hitting at the same angle and speed;

[0162] Record the acceleration peak value and vibration duration at the moment of hitting in real - time;

[0163] Each sample is tested 3 times, and the average value and fluctuation range are taken.

[0164] 2. Subjective comfort test process

[0165] Each tester uses the two samples to hit the ball in turn;

[0166] Keep the sample structure unknown to maintain blind testing;

[0167] Fill out an anonymous evaluation questionnaire;

[0168] Summarize the scores and calculate the mean and deviation.

[0169] According to the above experimental steps, experimental data are obtained and recorded in Table 1. The content of Table 1 is as follows:

[0170] Table 2. Vibration response and subjective comfort score results of different racket structures

[0171]

[0172] The experimental results show that the embodiment with a double-layer TPU foam structure exhibits significant acceleration reduction and vibration time shortening in the vibration test. The fundamental reason is that the TPU foam layer has a microporous elastic structure, which can quickly compress and absorb part of the mechanical energy when subjected to an instantaneous impact load, reducing the conduction intensity of energy towards the handle direction. Compared with the structure without TPU, the peak acceleration in the vibration response has decreased by nearly 40%, and the vibration decay time has also been significantly shortened, demonstrating good primary damping effect. This physical mechanism effectively blocks the high-frequency vibrations generated during hitting, reducing the instantaneous vibration sensation and structural rebound.

[0173] From the subjective experience, the buffering effect of the TPU layer is not limited to the weakening of physical vibration, but also has a softening effect on the hand feedback. The user rating data shows that the embodiment has achieved high scores in both the "comfort" and "shock absorption" dimensions, which is closely related to the "transition soft layer" formed by the material in the structure. As an intermediate layer between the carbon fiber hard shell and the honeycomb core, the TPU foam body forms a stress gradient region with its soft elastic structure, which can effectively smooth the structural impedance difference during the force wave conduction process and weaken the locally concentrated reverse reaction force. This stress transition mechanism makes the ball feel soft, without generating a sudden vibration and numbness sensation, and further extends the linear perception time during hitting, improving the operation stability.

[0174] In terms of the overall structural behavior, a synergistic mechanism is formed between the TPU damping system and other functional layers of the composite racket, achieving a balanced design that takes into account both structural strength and dynamic comfort. Compared with the configuration in the comparative example with only a rigid support structure, the multi-layer composite of the embodiment not only provides good seismic absorption ability, but also maintains the morphological stability of the honeycomb core. This "rigid-flexible-rigid" distribution structure exhibits excellent energy dissipation ability under high-frequency loads, while avoiding delamination or local stress damage between materials, providing sustainable dynamic response performance for the racket.

[0175] Experimental Example 3:

[0176] Purpose of the experiment: By simulating long - term repetitive hitting conditions, evaluate the fatigue durability and performance retention ability of rackets under different structural designs, including structural damage conditions, mechanical property degradation trends, etc., and provide a basis for judging the long - term service performance of rackets.

[0177] Specimen preparation:

[0178] C1: Carbon fiber + TPU + honeycomb core (Example 1);

[0179] C2: Glass fiber + TPU + honeycomb core (Example 2);

[0180] C3: Carbon fiber + honeycomb core (without TPU, Example 3);

[0181] C4: Honeycomb core + glass fiber (without TPU), Comparative Example 2;

[0182] C5: Honeycomb core + epoxy (without reinforcement), Comparative Example 3;

[0183] Prepare 2 pieces for each group, a total of 10 pieces of samples, all in physical size.

[0184] Experimental equipment and test parameters:

[0185] Fatigue hitting test machine (mechanical swing - arm type);

[0186] Frequency: 1.2 Hz;

[0187] About 72 hits per minute;

[0188] Total number of hits: 100,000 times;

[0189] Simulated ball speed: 90 km / h;

[0190] Post - test mechanical property test;

[0191] Three - point bending modulus (same as Experiment 1);

[0192] Visual observation (surface cracks, delamination, deformation);

[0193] Sample mass change (accuracy of ±1 g);

[0194] Experimental procedure:

[0195] 1. Fatigue simulation hitting process

[0196] Install the racket sample on the fatigue test stand, fix the angle and posture;

[0197] Start the equipment, continuously hit until the set number of times, and record whether it fails midway;

[0198] Take a photo every 20,000 times to record possible structural changes;

[0199] After 100,000 strikes are completed, remove the sample for subsequent testing.

[0200] 2. Subsequent Performance and Damage Assessment

[0201] Conduct three-point bending mechanical tests to obtain the comparison of the flexural modulus before and after fatigue;

[0202] Take photos to record surface damage;

[0203] Weigh and record the mass loss;

[0204] Sort out the fatigue retention rate and damage level.

[0205] According to the above experimental steps, obtain the experimental data and record the experimental data in Table 1. The content of Table 1 is as follows:

[0206] Table 3. Performance Changes and Damage Records of the Racket Sample after Fatigue Testing

[0207]

[0208]

[0209] The experimental results show that after the sample of the embodiment undergoes 100,000 simulated strikes, the overall structure still maintains good mechanical properties. The decline range of its flexural modulus is controlled between 5% and 10%, and no structural failure occurs. This performance stems from the interlayer synergistic mechanism of the materials in the composite structure: the carbon fiber layer provides the main support framework, the honeycomb core acts as a lightweight inner core to resist shear deformation, and the TPU layer effectively slows down the trend of microcrack propagation caused by continuous impact. Under continuous dynamic loading, the viscoelastic behavior of TPU plays a "buffering and damping" role, dissipating part of the vibration energy inside the material, slowing down the stress accumulation at the interface layer, and significantly inhibiting the propagation speed of fatigue microdamage.

[0210] In contrast, the control samples without the TPU structure (such as C4 and C5) show obvious deterioration and even premature fracture during fatigue. In particular, C5 ruptures after more than 20,000 strikes. The fundamental reason is that there is a lack of a transition soft layer in its structure, so that all energy impacts directly act on the interface between the honeycomb core and the surface layer, resulting in shear concentration and interface debonding. The honeycomb structure itself is relatively sensitive to repeated stress. Without a shock-absorbing medium to share the impact, its thin walls are extremely prone to buckling deformation and fatigue cracks, thus accelerating the structural failure. In contrast, the intervention of TPU provides an elastic transition region, which not only absorbs energy but also establishes a better stress distribution gradient at the interface, effectively protecting the overall stability of the composite structure.

[0211] From the perspective of the microscopic mechanism of material behavior, the TPU foam layer exhibits a typical hysteresis loop energy dissipation mode under repeated loading conditions. This non-linear hysteretic characteristic can effectively delay the composite structure from entering the failure phase. At the same time, its closed-cell foam structure endows it with a certain recovery ability. Even after local compressive deformation, it can still largely return to its original state, avoiding the accumulation of irreversible damage. This enables the embodiments to not only maintain stability in fatigue performance but also possess good structural memory and self-buffering ability during long-term service.

[0212] 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. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A honeycomb core racket with foaming material, characterized in that, Comprising: A honeycomb chip, which is used to form the internal support structure of the racket, with a side length of 3 - 10 mm and a thickness of 8 - 20 mm; A foamed elastic material layer, which is adhesively attached to at least one side of the honeycomb chip; A fiber reinforced layer, which covers the outer surface of the foamed elastic material layer, and the fiber reinforced layer is one of carbon fiber, glass fiber or Kevlar material; The honeycomb chip, the foamed elastic material layer and the fiber reinforced layer are laminated to form a composite board; The composite board is cut to form a racket body, and a handle connection part is provided.

2. The honeycomb core racket with foaming material according to claim 1, characterized in that, The honeycomb chip is an aluminum honeycomb core, an aramid paper honeycomb core or a polymer honeycomb core.

3. A honeycomb core racket with foaming material according to claim 1, characterized in that, The foamed elastic material layer is a thermoplastic polyurethane material.

4. A honeycomb core racket with foaming material according to claim 1, characterized in that, The fiber reinforced layer is adhesively attached to the foamed elastic material layer by hot pressing or cold pressing.

5. A honeycomb core racket with foaming material according to claim 1, characterized in that A protective edge structure is provided at the edge of the racket, and the handle is fixed to the racket body by adhesive bonding or mechanical connection.

6. A processing technology for a honeycomb core racket with foaming material, according to any one of claims 1-5, a honeycomb core racket with foaming material, characterized in that, Including the following steps: S1. Provide a honeycomb chip; S2. Adhesively attach the foamed elastic material layer to at least one side of the honeycomb chip; S3. Set a fiber reinforced layer outside the foamed elastic material layer, and the fiber reinforced layer is one of carbon fiber, glass fiber or Kevlar material; S4. Stack the honeycomb chip, the foamed elastic material layer and the fiber reinforced layer and then perform a forming process, and the forming process is any of the following methods: Thermoforming: Perform die pressing through a hot pressing mold at 180°C - 220°C and a pressure of 60 tons - 100 tons; Cold forming: Adhesively attach at room temperature by a pressing method, with a pressure of 20 - 50 tons, and cut to form a racket structure; Combined hot and cold forming: First perform thermoforming on part of the structure, and then perform cold pressing and adhesion; S5. Cut and trim the formed structure, and install a handle assembly.

7. A processing technology for a honeycomb core racket with foaming material according to claim 6, characterized in that, The foamed elastic material layer is formed by a supercritical fluid foaming process.

8. A processing technology of a honeycomb core racket with foaming material according to claim 6, characterized in that, A hot melt adhesive bonding layer or an epoxy resin glue layer is provided between the foamed elastic material layer and the fiber reinforced layer.

9. A processing technology for a honeycomb core racket with foaming material according to claim 6, characterized in that, In the combined hot and cold forming method, first perform hot pressing treatment on the honeycomb chip and the first fiber reinforced layer, and then adhesively attach the foamed elastic material layer and the second fiber reinforced layer by cold pressing.

10. A processing technology for a honeycomb core racket with foaming material according to claim 6, characterized in that, A binding strip is provided on the outer edge of the formed structure, and a handle, an identification layer and an anti-slip tape are installed after forming.

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