2019 Composite RTM Vacuum Closed Mold Process Practical Training

 

Development and application of composite liquid molding technology.

 

The content of the lecture is mainly divided into six parts:

 

Part 1, Overview of LCM Molding, the main contents include the definition of LCM, process principle, process composition, key process, main influencing factors of the process, development history, process advantages and disadvantages, and requirements of the resin system;

 

Part 2, Classification, characteristics and applications of LCM processes, the main contents are resin transfer molding RTM, vacuum assisted resin transfer molding VARTM, lightweight resin transfer molding L-RTM, resin infusion molding SCRIMP, resin film infiltration process RFI, structural reaction injection process SRIM, high pressure resin transfer molding HP-RTM, thermoplastic resin transfer molding T-RTM, surface resin transfer molding Surface-RTM, prepreg assisted resin transfer molding SQ-RTM, thermoplastic film assisted resin transfer molding Film-RTM, pultrusion-resin transfer molding Pultrusion-RTM, super resin transfer molding Ultra-RTM and other specific LCM processes. The process characteristics, process principles, process, typical application parts;

 

Part 3, LCM Analysis of process preform preparation technology, the main contents include fiber preform technology overview (technical requirements), textile preforming technology (flat fabric, three-dimensional fabric) fabric form (flat-plain cloth, square fabric, twill, satin fabric, wrinkle-free fabric; three-dimensional-woven fabric, orthogonal interlaced fabric, 2D braided fabric, 3D braided fabric, 2D/3D stitching technology-single needle stitching technology, double needle, chemical stitching technology, VAT fiber variable angle traction machine paving preforming technology), advantages and disadvantages, application scenarios, typical application parts, setting agent setting technology, including short fiber injection preforming P4A technology, manual paving preforming, hot pressing preforming definition, process, process preparation, common problems, typical application parts;

 

Part IV, analysis of the development trend of mold filling flow control technology, the main contents include Darcy’s law, resin system, permeability (unidirectional saturated flow method, unsaturated radial method), thickness change measurement, injection method (edge edge point/line injection, center injection, surrounding injection), working pressure, defect formation mechanism/control, corner effect, edge flow effect, process simulation (RTM-Worx, PAM-RTM);

 

Part V, LCM molding equipment technology development analysis, the main content is the fiber preform processing center, including equipment for short fiber injection preform, hot pressing preform, 2D weaving technology to prepare preform, 3D weaving technology to prepare preform, RTM injection system, including resin storage tank, heat exchange system, high pressure metering pump, resin hedge mixing head, hydraulic press, including translatable work table, reversible work table, short stroke hydraulic press, molding mold, clamping and transfer equipment, including fiber preform adsorption fixture, composite product adsorption fixture, machining equipment, including mechanical cutting, high pressure water cutting, laser cutting, etc.;

 

Part VI, typical product LCM process examples, mainly including Taili Mould I-beam RTM molding, Sikorsky UH-60 Fuselage top cover SQRTM molding, UH-60 SARAP fuselage verification parts, soft mold auxiliary thrust cylinder RTM molding, Torres wing (dry fiber placement + VARI integral infusion molding)

 

L-RTM mold making process and precautions.

 

L-RTM mold production mainly follows

① Read the drawings to see if the product is suitable for the L-RTM process, whether it needs to be modified, demoulding slope, embedded parts, local thickening, block, etc., and increase the skirt and thickness of the L-RTM mold based on the original drawing;

② Model processing, you can choose block substitute wood, paste substitute wood, wood, high-density PU foam or PS foam;

③ Model (substitute wood processing), use the machining center to process the model, after processing, it needs to be measured according to the drawings. If the surface needs to be sealed, scrape the putty and then spray the easy-to-grind primer;

④ Model (easy-to-grind primer treatment), the recommended spraying amount is 300g/m2, spray first hard and then easy, and finally spray the large area of ​​the model. When grinding, determine the sandpaper mesh and grind according to the product configuration;

⑤ Model (high-gloss gel coat treatment), the recommended spraying amount is 200g/m2, spray first hard and then easy, and finally spray the large area of ​​the model. When grinding, Determine the mesh number of the sandpaper and polish according to the configuration of the product;

⑥ Demolding treatment, select high-quality demoulding agent, and ensure the cleanliness and appropriate temperature of the coating environment;

⑦ Mold gel coat spraying, the recommended dosage is 800g/m2 (1000g/m2 for small molds), and it is necessary to spray thin layers multiple times to avoid excessive thickening in some areas, and spray the difficult ones first and then the easy ones;

⑧ (Fatigue-resistant layer) Surface mat paste, make sure the surface mat is dry, and confirm the gel time of the resin. The surface mat should be pasted when the gel coat is sticky but not sticky, which can reduce the amount of resin;

⑨ (Fatigue-resistant layer) Chopped mat paste, the chopped mat should also be ensured to be dry, and the paste time close to the gel coat layer should be arranged as much as possible during the day. Before pasting the chopped mat, make sure that the surface mat is completely cured and the bubbles have been removed. For the first two layers of the mold with complex surface, choose 150-300gsm mat, and the mold reinforcement layer mostly chooses zero shrinkage resin, and its thickness is recommended to be 3mm Above;

⑩ (sandwich layer) production, pay attention to fit, you can use special putty to stick it, or mix zero shrinkage resin and filler;

⑪ Wrapping layer production, first check whether the sandwich is firmly glued, handle the corners to make a smooth transition and polish, and then paste the wrapping layer;

⑫ Steel frame production, remove stress after the steel frame is welded, if there is no condition to remove stress, you can use silicone to bond the steel frame;

⑬ Positive mold is completed, use high-grit water sandpaper for processing, and use pure cotton cloth to wipe in one direction when cleaning;

⑭ Mold cavity processing, wax sheet paste to ensure the ambient temperature, high temperature will make the wax sheet soft and deformed, low temperature will make the wax sheet hard and poor bonding, each wax sheet should be laid evenly, and there should be no air trap under it;

⑮ Air chamber production, the key is to ensure the sealing effect of the latter two layers, reasonable design before laying, and ensure that the pre-buried internal and external sealing channels are not deformed and firmly glued when laying;

⑯ Injection port and exhaust port design, first consider the success rate, then consider Reduce workload and save materials; ⑰ When making the back mold, the resin used should take into account the shrinkage effect, and the paste making of the sealing channel and the air chamber should be arranged in a reasonable manner to ensure that there is no shrinkage and deformation; ⑱ After the back mold is completed, the finish of the back mold is not required to be high, but the sealing of the injection port and the exhaust port is very important. As long as there is a slight leak in the back mold, it will have a great impact on the product.