Theoretical study and physical tests of circular hole-edge stress concentration in long glass fiber reinforced polypropylene composite

The long glass fiber reinforced polypropylene (LGFRP) composite has been widely used in automotive components due to its remarkable advantages of high mechanical properties and flexible design features. Automotive structural components usually suffer various intrinsic hole-edge stress concentration in mechanical joints. Thus, the objective of this work is to investigate the circular hole-edge stress concentration of the LGFRP composite. A theoretical model, which is in view of cutting area and damage factor, is originally developed to predict the hole-edge stress concentration in LGFRP composite with regard to the hole size effect. Corresponding physical tests were conducted under tensile loading monitored by a digital image correlation (DIC) system. The experimental results reveal that the influenced area of the stress concentration is within the range of four times of the hole radius. The theoretical predictions are in good agreement with the experimental results. The stress concentration factor (SCF) is calculated to demonstrate that SCF increases with the increasing circular hole radius. The conclusions obtained from this work lay the basis on the mechanical performance of the LGFRP composite subject to hole-edge stress concentrations, and is of importance to rationalize appropriate design of the LGFRP composite in automotive components.