Numerical and Experimental Evaluation of Scarf Repaired Composite Panel Under Tensile Loads

The use of composite materials in aircraft structural components has increased in the past few decades as a result of many advantages they offer in terms of superior combination of stiffness, strength, and low density. CFRP composites are the advanced composites are extensively used in primary aircraft structures. However, damage can occur during the service life of composite structures due to several causes such as environmental and/or external loading conditions. To continue their operation, the damaged parts need to be replaced or repaired, and the repair solution is in some cases adopted because of economic benefits. The main purpose of a structural repair is to fully support applied loads and transmit applied stresses across the repaired area. In the present study, three different composite panels (undamaged, damaged, and repaired) are evaluated for their tensile strengths, in order to examine the effect of damage on the strength reduction in the damaged specimen and to assess the performance of the scarf repaired panels shown in the Fig. 1 in regaining the strength of the undamaged panel. Carbon/Epoxy prepreg material was used to lay up sixteen-ply (1000 x 300 x 3.3 mm) [+45/-45/0/0/90/45/0/0]s quasi-isotropic laminate panels. Three configurations namely the undamaged, damaged (with center hole) and the scarf repaired CFRP panels are analyzed for their strengths using ANSYS software. The tensile strength prediction of the undamaged panel, panel with centered hole and a repaired panel is carried out applying the Tsai-Wu failure criterion. Subsequently, the strength recovery rates of the scarf-repaired structures were calculated to evaluate the mechanical performance with different scarf angles. Further, these laminated composite panels are tested under tensile loading conditions, by Servo-hydraulic Universal testing machine. The tensile strength of each of the panels determined both numerically and experimentally were compared and exhibited good agreement with each other.