مهدي صحرانورد

Friction lap welding was used to join aluminum with glass fiber–reinforced thermoset polymer (GFRP) using a thermoplastic interlayer. The effect of different welding parameters on joint strength an‎d fracture surfaces was investigated, an‎d the optimal welding parameters were determined using the Taguchi method. Results revealed that low heat generation led to weak mechanical interlocking between GFRP an‎d the thermoplastic interlayer, while high heat generation caused degradation of the aluminum/thermoplastic polymer interface. The tool traverse speed was found to be the most influential parameter in terms of joint strength, followed by plunge depth an‎d rotational speed. Moreover, thermal measurements were conducted during the welding process using thermocouples. An uneven thermal distribution was discovered across the overlap area due to dissimilar substrates. This issue was resolved by incorporating aluminum thermal insulation, resulting in improved heat distribution an‎d a significant enhancement of 94% in joint strength. Scanning electron microscopy (SEM) was employed to identify joining mechanisms an‎d examine the effect of welding parameters on joint microstructure. Furthermore, Fourier transform infrared spectroscopy (FTIR) was used to investigate chemical bond formation at the aluminum/thermoplastic polymer interface. The results showed that the joining mechanisms involved mechanical interlocking between the thermoplastic interlayer an‎d aluminum, as well as chemical bonding, penetration, an‎d intertwining between the thermoplastic interlayer an‎d the thermoset composite. The Mode-I fracture in friction lap-welded aluminum-to-thermoset GFRP joints with a thermoplastic interlayer is investigated. Double cantilever beam (DCB) tests were performed, using digital image correlation (DIC) to monitor crack propagation an‎d calculate the strain energy release rate (SERR). The compliance-based beam method (CBBM) an‎d crack tip method (CTM) were compared, with CBBM incorporating fracture process zone (FPZ) effects an‎d root rotation. Scanning electron microscopy (SEM) revealed two key joining mechanisms, including mechanical interlocking between the thermoplastic interlayer an‎d aluminum, an‎d polymer penetration into GFRP fibers. examining the fracture surface exhibit that the crack path initially propagated at interlayer polymer inducing cohesive failure an‎d by increasing the load deviated into GFRP causing significant fiber bridging. These mechanisms induced fiber bridging during testing, reflected in the traction-separation curves. A trilinear cohesive zone model (CZM) was developed to capture bridging effects, an‎d finite element simulations yielded load-displacement curves aligning closely with experimental results. The study advances the understan‎ding of hybrid joint fracture behavior an‎d demonstrates the efficacy of CZM for modeling complex failure in thermoplastic-interlayered, friction-welded aluminum-thermoset GFRP systems. Finally the Mode-II fracture behavior of friction lap-welded aluminum-to-thermoset glass fiber reinforced polymer (GFRP) composite joints, incorporating a thermoplastic interlayer, was investigated through an integrated experimental an‎d numerical approach. End-notched flexure (ENF) specimens were fabricated an‎d tested under three-point bending. The strain energy release rate an‎d the traction-separation response for the cohesive zone model (CZM) were determined using the compliance-based beam method (CBBM). This data reduction scheme was selec‎ted for its ability to account for the equivalent crack length an‎d the presence of a non-negligible fracture process zone (FPZ). To ensure pure Mode-II loading conditions, the bending stiffnesses of the substrates were equalized by thickness adjustment, thereby eliminating contributions from Mode-I fracture energy due to stiffness mismatch. The joining mechanisms were examined using scanning electron microscopy (SEM), revealing mechanical interlocking at the interface, adhesion by the thermoplastic polymer, an‎d resin penetration into the aluminum surface micro-features; these mechanisms collectively contributed to the overall joint integrity. Furthermore, a trapezoidal traction-separation law was adopted to accurately simulate the experimental response, including the combined effects of interlayer polymer plastic hardening an‎d fiber bridging observed in the joints. The numerical results demonstrated reasonable agreement with the experimental data.

جوشكاري اصطكاكي لبه اي , كامپوزيت گرماسخت , پليمر گرمانرم , رفتار شكست در بارگذاري مود 1 , مود 2

Friction lap welding , Thermosetting , Hybrid joint , Thermoplastic , Taguchi method , Microstructure , Mode-Ⅰ fracture , Dissimilar joint , Strain energy release rate , Cohesive zone model , Mode-Ⅱ fracture , End-notched flexure test

Mehdi Sahranavard

dr Hadi Khoramishad