Molding Technology And Thickness Distribution Optimization For Injection Molding Of Short Fiber Reinforced Plastic Product

Short fiber reinforced plastic(SFRP)is widely used in aerospace,automotive,ship manufacturing,petrochemical,electronics and other fields for its high specific stiffness,high specific strength,strong functionality and designability.With the rapid development of plastics industry in recent years,there is a great demand for the technology that can promote the mass production of fiber-reinforced composites.Using injection molding method for processing short fiber reinforced composites is now one of the most commonly used method.This method has the advantages of simple processing,low cost and mass production as well as it can achive the manufacturing of products which have complex shapes and sufficient stiffness.Taking injection molding of short fiber reinforced plastic product as the research object,this work studied the optimization of forming process parameters,gate location and product thickness distribution under the structural service condition by numerical simulation method.Firstly,an efficient optimization approach for coupling design the gate location and processing parameters is developed on the basis of the EGO optimization algorithm which is made up of EI function and Kriging surrogate,then taking the maximum failure criterion of the product in service as the objective function,a verification example is designed,and the maximum failure criterion is reduced by 40% before and after optimization.Secondly,we develop a new method to optimize the thickness distribution of SFRP products which is based on Nelel-Mead optimization algorithm and the general idea of dimensionality reduction and validated by an example which is aim to reduce product weight.The optimization results showed that the overall thickness distribution of 2,468 units was successfully described by 10 design points,and the weight of the products was reduced by 35.7375% while the service conditions were satisfied.Finally a hierarchical optimization approach for gate location,forming process and the thickness distribution of SFRP products is developed which is considered of the local fiber orientation and failure criteria under service conditions n the basis of propose and verify of the gate location and processing parameters coupling design approach and the thickness distribution design approach.The feasibility and engineering practicability of the algorithm are verified by two calculation examples of motor mounting bracket and Steering oil tank clamp and bracket assembly.The maximum failure criterion was reduced by 28.82% which is from failure to non-failure and the weight of the bracket was reduced by 21.09% before and after the optimization of the motor mounting bracket.The optimization results achieved the expected design purpose which the optimized product has greatly improved its bearing capacity while reducing its weight.Steering oil tank clamp and bracket assembly example is to use the thickness of the 20 design points changes successfully describe the overall thickness change of 4850 units.The maximum service displacement of the assembly decrease 90.90%,the maximum Von Mises stress reduced 40.56% and the biggest failure criterion decrease by 57.74% before and after optimization.The weight of the assembly decrease 79.82% compared to the initial steel material which total weight is 1.253 kg.The optimized result has reached the design requirements of the assembly.