Experimental Investigation of the Compaction and Tensile Strength of Co-cured Skin-to-Stiffener Structures

The integral technology of co-curing has been attracted increasing attention due to its resulting in fewer parts and reduction the assembly times and cost of aircraft structures. In this study, an experimental co-curing technique was applied to fabricate T-stiffened panels in the autoclave, with an emphasis to investigate experimentally on the influence of tool assembly schemes on the manufacture and performance evaluation of co-cured panels. The pressure transferring characteristic of the tools was measured. The thickness analysis and the microscopy observation were examined to discuss the influence of various tool assembly schemes on the compaction of T-stiffened panels. Moreover, a special pull-off test was performed to evaluate the effect of the manufacturing quality on the mechanical performance. The experimental results indicated that during co-curing period, an interesting observation was found that the manufacturing quality of T-stiffened panels was significantly influenced by a position limit for the tools. In case of absence of a position limit for the tools, a micro-cut showed that the fiber waviness obviously appeared in skins and stiffener corners of T-stiffened panels, which was extremely attributed to the pressure distribution in stiffener corners. Applying a position limit for the tools can effectively eliminate the fiber waviness in stiffener corners and a well consolidated T-stiffened panel with uniform thickness was obtained, almost free of fiber waviness and resin-rich defect. Under tension condition, the fiber waviness in stiffener corners remarkably caused a decrease of the initial damage load, but showed no significant influence on the peak load.