Research On Proccessing Parameters Control And Mechanical Properties Of The Π-Stiffeners With Advanced Pultrusion

Stiffener is an important form of lightweight structures. It has been widely applied inthe field of aircraft structures offering to improve the stiffness of structure and the capacityof resistance to post-buckling. For composite stiffeners, co-curing or co-bonding withcomposite panels can make full use of structure advantages of composites, which cancontribute to quality improvement and cost reducing. So the manufacturing method andperformance of these kinds of part are significant for the production of stiffeners.Advanced pultrusion which is a new low-cost manufacturing composite method, is theimportant trend of the future. Based on self-developed ADP prototype of Nanjing Universityof Aeronautics and Astronautics (NUAA), the researchers are conducted in these aspects:a. According to the features of the self-developed ADP prototype, determined is theAdvanced Pultrusion (ADP) processing parameters, analyzed is the manufacture processing,parameter control strategy and control scheme. And the hardware system is completed by therealization of automatic operation and the building of remote PC control of the prototype aswell.b. In addition, the Π-stiffeners are successfully manufactured, after several trials andimprovement, such as the optimizing of action time intervals, tension rising of the feedingprepreg and additional PTFE film on heating plate. Moreover, the appearance, overall,dimensions and mechanical properties of the Π-stiffeners are evaluated through flexural,tensile and in-plane shear tests which shows that the stiffeners are well produced comparedto the molded components.c. Furthermore, conducted are the tensile and flexural tests of products which areprepared in different curing degrees are prepared and later cured again, and the result showsthat the properties are little influenced by curing degree. Also, analyzed is the influence bycuring degrees of the flanges, on the tensile property (shear loaded) of the single-lap jointparts which are constructed though the co-curing between prepregs and flanges in differentcuring degrees, and it indicates that the tensile property are better with the decreasing of theflange’s curing degree. However, by taking into consideration of all the factors, such as theshape retention ability and cost, the optimized processing parameters of the Π-stiffeners (13layers made by C/Bisphenol-A epoxy prepregs) for co-curing, are determined as curing time of10min, heating temperature of130°C, pressure of0.3MPa and step distance of10mm.