| The composite stiffened wall structure reinforced with hat-shaped stiffeners is widely used in large aeronautical structures due to its high specific stiffness,specific strength and structural stability.With the development of large aircraft,there is a great demand for the preparation of extra long hat stiffeners.Advanced Pultrusion(Advanced Pultrusion,ADP)technology enables the production of long profiles with short dies at low cost.In this paper,the research of advanced pultrusion technology for hat-shaped stiffeners was carried out.The ADP system was designed,the pultrusion process was developed,the long stiffener was prepared and the defects were systematically optimized.(1)According to the design requirements of the hat-shaped stiffener,an automatic lay-up scheme was designed.In order to ensure the direction of ± 45 ° and 90 ° to achieve Laying with the tension,the roll grouping and tape laying programs are designed,through the roll arrangement and tension control to achieve the prepreg automatic lay-up with tension.(2)The preforming process of the hat-shaped stiffener was analyzed,and the scheme of preform control was established by using the preforming die.The deformation model of prepreg preforming process was established,and the fiber path lengthwise and Lateral planning,to complete the design of preform mold,the resulting preforming model had the same transverse fiber length and the maximum longitudinal length change rate of 0.61 ‰.Aiming at the phenomenon of multi-layer prepreg sliding in the R corner zone during the preforming process,the preforming process was studied to reduce the interlayer slip resistance and the preforming temperature was 100 ?.The preform prepared under the mold and the process was examined metallographically,and the defects of the cross section of the cross section fiber in the R corner area were smooth and without crease rupture,which verified the feasibility of the preforming scheme.(3)According to the characteristics of advanced pultrusion system,the sample curing process was confirmed by the DSC test of the sample.The curing temperature was 181 ° C and the curing time was 30 min;The profile forming pressure of the prefabricate stiffener is analyzed,the soft and hard die compound pressing process is proposed.The finite element analysis is used to determine the size of the soft mold to ensure uniform pressure on the workpiece surface.Planning the heating scheme of the hot pressing device,calculate the heating power and achieve the precise control of the temperature;(4)Completing ADP system construction;designing the traction device to realize the step-by-step advancement of the parts;using PLC as the master control unit to control the timing of each agency movements of the ADP system to ensure the automatic operation of the equipment;and developing the touch screen operation interface to achieve a Human-computer interaction.The initial trial production of the hat-shaped stiffener and the analysis of the step-on defects on the surface of the workpiece were carried out.The pretreatment process was proposed and through the design experiment to determine the pretreatment temperature of 160?,pretreatment pressure of 0.3MPa.After the process was improved,the preparation of the long stiffener was carried out again.The finished product surface quality was intact and the defect of the stepping grain disappeared and met the requirements. |
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