Infrared Heating Technology for Automated Fiber Placement

Prepreg stickiness is the adhesion between prepregs or between a prepreg and a mold in lay-up process.It is critical for automated fiber placement,because the stickiness should be small for smooth transport,as well as large enough on the laying surface for a good placement performance.To ensure prepreg stickiness always being in the optimum laying window,placement temperature should be changed according to the laying speed.In our work,the relationship between laying speed and emissive power of heating lamp was studied.The heat transfer process between heating lamp and laying surface was analyzed and the control equation of dynamic temperature was derived.Finally,the infrared heating system was built and its effectiveness was verified based on placement experiment.

Effect of gap and overlap on mode Ⅱ interlaminar fracture toughness of automated fiber placement prepreg laminates

Automated Fiber Placement(AFP)technology facilitates the manufacturing process of composite structures with complex geometry owing to its high efficiency and accuracy.However.the unavoidable imperfections induced by the automated layup method bring challenges to the stability of the final mechanical properties of composites.The influence of AFP-induced gaps and overlaps on the modeⅡinterlaminar fracture process of oven-cured laminates is experimentally investigated and explicitly revealed.End-Notched Flexure(ENF)tests were performed to measure the interlaminar fracture toughness of unidirectional laminates under three different defect configurations,namely"Gap""Overlap"and"Gap&Overlap".A marginal decline(about-1.2%in non-precracked tests,-5.1%in precracked tests)and an obvious increase(about 15.2%in nonprecracked tests,5.2%in precracked tests)in fracture toughness were observed for the"Gap"group and the"Overlap"group,respectively.Fractographic studies which involve the metallographic observation and Scanning Electron Microscopy(SEM)observation revealed that the increases in fracture area and crack length helped improve the fracture toughness of the Overlap"group.However,the resin-rich area with high porosity induced by gaps was detrimental to the delamination resistance.To capture the interlaminar stress distribution local to imperfections,a three-dimensional numerical model was established.Gap defects facilitate the local delamination process,and the overlap defect postpones the damage onset and the propagation.

Thermal management for thermoset automated fiber placement based on infrared heater structure arrangement

Layup temperature is a vital factor that affects the production quality of automated fiber placement for thermoset composites.For high quality production,this paper proposes a new prediction model of layup temperature by considering the structure of infrared heater of automatic fiber placement equipment.The model was first verified by comparing with the temperature results of layup experiments.Then a prediction on the effects of heater structure arrangement on layup temperature was conducted in the model.The research shows that the length of infrared tube and the radian of reflective-film have significant influences,rather than other parameters.According to this investigation,a heater structure-based heating strategy was presented in the paper to efficiently achieve constant temperature control in variable speed layup process.

Deviation-Rectifying Control of Carbon Fiber Prepreg Slitting and Winding Machine

With the growing needs of prepreg tapes for the automated fiber placement(AFP),the deviation-rectifying of prepreg in slitting process was investigated on a self-developed 16-tow prepreg slitting and winding machine.The process of slitting and rewinding of prepreg tape was introduced,and the reason of prepreg tape deviation in slitting process was analyzed.In order to ensure the quality of the narrow prepreg slits,the application of the fuzzy PID algorithm in a closed-loop control system was discussed.A fuzzy PID algorithm was designed by combining fuzzy rules and PID controller.By applying it to precise deviation-rectifying control strategy,the automatic control of rectification could be achieved with accuracy of 0.1 mm,which satisfies the requirement of the prepreg tape both in slitting quality and layup quality for AFP.