Study On Variable Long Fiber Reinforced Reaction Injection Molding Technology And Products Quality Control

Variable long fiber reinforced reaction injection molding (VLFRRIM) is a new process for composite material molding technology which was developed based on reinforced reaction injection molding and variable fiber injection technology.Although to be applied in some of the areas, the basic theory research of VLFRRIM technology is deficient and lag. In order to reduce VLFRRIM products’defect, improve VLFRRIM products’quality, in this paper, the mutual influence discipline of VLFRRIM important processing conditions、 evolution of Material forms structuren the morphology and properties of VLFRRIM products have been systemically investigated through the theoretical analysis and test. The results of these studies have therefore achieve the goal of VLFRRIM products’quality improving and cost of production reducing, finally, The preparation of car inner decoration products according to the best optimal process parameters from this study, verify the feasibility of our research project. The main research contents are as follows:(1) Research on the VLFRRIM key technology such as process theory, material system, equipment system, VLFRRIM products and mould structure design systemically through the theoretical of reinforced reaction injection molding. Sum up the VLFRRIM products’common defects and analyzes its reasons,then, developed a whole solution project for the development of VLFRRIM products of Car inner decoration.(2) Effects of the main processing parameters such as type of fiber (glass fiber, plant fiber, carbon fiber), fiber contents and length, mold material temperature, mixture material temperature and compound die pressure on the permeability of long fiber were discussed, established a model which respect to technology parameters and permeability. It proves that each technology parameters have significant effect on permeability; The reaction kinetics mode during makings polymerization was established through adiabatic temperature rise experiments and brookfield rheometer, this model can exactly predict the curves of the temperature of the Makings system, the conversion of isocyanate and the mold cavity temperature during filling and curing; Research on curing kinetics of VLFRRIM mixture material system with dynamic DSC test, focus on the influence of dynamic equation, reaction activation energy, reaction series during inject different fiber into PU system. It turn out that,with injection of fiber, the apparent activation energy and the former factor have a significant increase(The best fiber injection can increase2times to the original), In the same heating rate, reduces the max curing reaction rate, extends curing reaction time, whatmore, each reaction order is about1;Fluidity of VLFRRIM mixture material system get characterization with flow index and density distribution coefficient, Effects of processing parameters such as type of fiber, fiber contents and length, mold material temperature on the fluidity were discussed. The study revealed that when length of fiber up to25mm, fiber contents exceed30%, fluidity of mixture material have a significant reduce.(3) Effects of various processing parameters such as type of fiber, contents and length of fiber, time of compound die, temperature and time of later aging on mechanical property such as tensile property, bending property and impact property, and hot prolapsed dimensional stability of VLFRRIM products were researched,the study revealed that injection of every type of fiber can improve mechanical property and dimensional stability of VLFRRIM products, among various processing parameters, contents and length of fiber are significant factors to property of VLFRRIM products, moreover, the relation between morphological structure evolution of VLFRRIM material and mechanical property is taked into research. Mass loss of VLFRRIM material get analysis through thermogravimetry, the result indicates that VLFRRIM material, which start disintegrate at the temperature of200℃has a good heat stability. Effects of processing parameters such as type of fiber, fiber contents and length, mold material temperature, mixture material temperature and compound die pressure on surface quality of VLFRRIM products such as restoration and warpage amount were discussed, with the increasing of fiber contents and length, surface quality of VLFRRIM products get a significantly improve.(4) Based on stress transmission theory of fiber composites and laminated plate theory, effects of dispersion of fiber properties, length distribution, orientation distribution and intensity distribution of fiber, as well as foam pore structure, size, and surface density on the property of the composite were synthetically considered, established prediction models of modulus, tensile strength and impact strength which respect to VLFRRIM material. The results show that when the fiber weight percent is less than15%, the equations were better in agreement with the experimental results, but when the fiber weight percent is more than15%, the prediction error is relatively large.(5) Designed orthogonal test with Taguchi method, effects of the main processing parameters such as fiber contents, fiber length, mold material temperature, mixture material temperature and time of compound die, the mass ratio of material on combination property of VLFRRIM products were analysised, Got the optimization of process parameters of several index; Conceptual optimized the bending modulus, impact strength and warping deformation through comprehensive valuation equation, obtain the optimum set of processing parameters. Combining with enterprise, prepared inner decoration products of car with the optimum set of processing parameters and other research techniques in this article, results shows that the products of VLFRRIM have better combination property, while reducing the amount of base material, and cost savings.