Resistance welded composite joints strengthened by carbon fiber felt: mechanical properties, failure modes and mechanism

Abstract

The joining of composite parts with weight reduction and cost saving is being developed to improve aircraft performance. The high-efficiency resistance welding technology was hence explored for joining glass fabric reinforced polyetherimide (GF/PEI) laminates in this work and a composite PEI films reinforced with carbon fiber felt (CFF) reinforced laminae was embedded into the interface of the welding region to enhanced the strength of the joints of GF/PEI. The effects of CFF incorporation on the welding speed and the lap shear strength (LSS) of welded joints were investigated in comparison with those of the CFF-uncontained welded joints. The CFF-incorporated resistance welding speed was accelerated and its LSS was enhanced evidently, the maximum LSS value reached 32 MPa. The fracture mode and mechanism of welding implants, which varied with tw from the linear tearing to the annular tearing due to the coupling effect of the improvement of PEI molten state and the occurrence of PEI thermal degradation, were illuminated according to the test results from ultrasonic C-scan and SEM.