Three-Point Bending and Cohesive Zone Analysis of Resistance-Welded Carbon-Fiber-Reinforced Polycarbonate to Aluminum 7075 Single-Lap Joints

Resistance-welded thermoplastic composite-metal hybrid joints may be useful for temporary or secondary aerospace repair concepts, but their small-coupon response is difficult to interpret because bending, peel, sliding and welding-induced residual stresses occur simultaneously. This paper presents an adapted three-point-bending study of six single-lap coupons made from carbon-fiber-reinforced polycarbonate and aluminum 7075. The test was used as a screening method to determine global stiffness, peak force and debonding behavior under a concentrated transverse load. The recorded force was converted to a nominal bending stress indicator using the test geometry. Peak forces ranged from 246.1 N to 293.7 N, with a mean value of 274.0 N. The corresponding nominal bending stress indicator ranged from 131.8 MPa to 157.3 MPa, with a mean value of 146.8 MPa. The apparent work per overlap area ranged from 0.615 mJ/mm² to 0.804 mJ/mm². The area under the force-displacement curve was not treated as fracture energy because it also includes adherend bending, contact work and residual-stress release. The calculated stress-displacement curves were used to calibrate an ANSYS cohesive-zone debonding model. The welding-induced residual state was introduced through an initial strain condition before mechanical loading. The calibrated model predicted a peak stress of approximately 156 MPa, corresponding to approximately 291 N. This value was about 6.3% above the experimental mean and remained within the experimental range.