Processing Parameter Analysis And Optimization Of Automated Tape Laying For Thermosetting Prepregs

It has been an eternal topic of aircraft design and manufacture to reduce the weight ofairplane structure. Composite materials emerging in the Nineteen sixties, havingadvantages of high specific strength, good high temperature resistance, impact resistance,corrosion resistance, fatigue resistance and lightweight, began to get more and moreextensive application on the aircraft design and manufacture. Automated tape laying (ATL)is a molding method of large composite wing and panel, having the characteristics of highproduction efficiency and low manufacturing cost. At present, ATL is still at the initialstage in China, especially for related research on ATL technology, and assessment oflay-up quality and placement suitability of prepreg still in the stage of qualitative analysis.This thesis focus on three aspects of lay-up quality of ATL for thermosetting prepreg, tackand drape for quantitative analysis, influences of ATL processing parameters on them wereanalyzed, and the lay-up process of ATL was optimized. The main contents are as follows:(1) A new grading criteria of lay-up quality on ATL was proposed for its quantitativeanalysis. Single-factor experiments were developed on the ATL processing parameters testplatform which was constructed by ourselves, influences of three process parameters, suchas hot-air temperature, lay-up pressure and lay-up velocity on lay-up quality wereanalyzed. Based on the results of single-factor experiments, using Box-Behnken responsesurface methodology (RSM), mathematical models was set up to forecast the relationshipbetween the processing parameters and lay-up quality, and influences of the processingparameters’ interaction effects on the lay-up quality were analyzed. Processing parametersfor both the best lay-up quality and the maximum lay-up velocity in the acceptable lay-upquality were forecasted.(2) Physical meaning of prepreg’s tack was discussed and the differences betweenprepreg’s tack and other areas of tack were pointed out. The existing measurement andcharacterization methods of prepreg’s tack were summarized, especially focus onquantitative measuring method of tack for detailed discussion, and the advantages anddisadvantages of various measuring methods were analyzed, and the advantages of “peeltest method" on the tack in ATL process was proposed. Then using “Average PeelingForce” quantitatively characterizing the tack of prepreg was proposed, and influences ofthe main processing parameters of ATL, such as out time, lay-up pressure, lay-up velocity,hot-air temperature etc., on prepreg’s tack were analyzed. The experimental resultsindicate that the tack increases first and then decreases with out time, while increases withhigher pressure of lay-up, higher temperature of hot-air and lower velocity of lay-up in therange of concentrations. (3) The meaning of prepreg’s drape was discussed, and the existing measurementmethods and quantitative characterization of prepreg’s drape were summarized. Using the“Max Bending Force” quantitatively characterizing the drape of prepreg was proposed andviscoelasticity of prepreg and influence of the main processing parameters of ATL, such aslay-up velocity, humidity, hot-air temperature, aging time etc., on prepreg’s drape wereresearched by “three point bending test”. The experimental results indicate that prepreg’sdrape increases with the higher temperature and humidity, but decreases with the longeraging time and lower velocity of lay-up. Finally, the engineering significance of drape testwas summarized, which provides a reference for the control of the processing parameterson ATL.