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ABSTRACT
We investigated the debonding on-demand (DoD) of adhesively bonded hybrid dissimilar joints by applying electromagnetic induction heating to the joint overlap section, wherein the epoxy resin is reinforced with iron oxide (Fe3O4) particles. Ti-6Al-4 V adherends were bonded with CFRP or GFRP adherends using neat/modified epoxy adhesive. DoD tests revealed that eddy current heating of Ti-6Al-4 V was a dominant heating mechanism of the joints while both eddy current and magnetic hysteresis of CFRP and Fe3O4 acted as a secondary heating factor. A low content Fe3O4 and thinner composite adherend reduced the time to failure of the joints. Likewise, CFRP required a shorter time for debonding compared to GFRP due to its electromagnetic properties. Modifications with 2 and 5 wt.% Fe3O4 for CFRP and GFRP joints led to 31% and 37% time reduction which will be crucial for energy-saving when debonding large structures. Remarkably, sandblasting improved the electromagnetic induction capabilities of Ti-6Al-4 V, leading to a notable increase in the heating rate, which jumped from around 20°C/s to 80°C/s. Sandblasting enhanced the surface roughness of the adherends but only the water contact angle of GFRP decreased considerably. Fe3O4 modifications increased the epoxy residue on the Ti-6Al-4 V surface from 26% to 99%. DIC revealed the strain distribution of bulk materials to understand the thermomechanical mismatches between the materials and the adhesive joints exhibited high peel stresses at the overlap ends. The low weight content (2 and 5 wt.%) of Fe3O4 exhibited beneficial effects on the mechanical, thermal, thermomechanical, wettability and lap shear strength.
Acknowledgement
CH thanks Nanyang Technological University for the financial support in the form a SINGA graduate scholarship. IS thanks National Research Foundation Singapore for financial support via Grant Number CRP29-2022-0041.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Nomenclature
| A | = | adhesive failure |
| Al | = | aluminum |
| BET | = | Brunauer – Emmett–Teller |
| CDCB | = | contoured double-cantilever beam |
| CTE | = | coefficient of thermal expansion |
| DMA | = | dynamic mechanical analyzer |
| E | = | Young’s modulus |
| EoLV | = | end-of-life vehicles |
| εy | = | failure strain in the y direction |
| FRP | = | fiber reinforced polymers |
| GIC | = | adhesive fracture energy |
| M | = | mixed failure |
| Ra,1 | = | arithmetic mean height in the axial direction |
| Sa | = | arithmetic mean height |
| Sp | = | maximum height of peaks |
| Sssk | = | skewness |
| Sz | = | maximum height of the surface |
| SLJ | = | single lap joint |
| σUTS | = | Ultimate tensile strength |
| tan δ | = | tan delta |
| Tg | = | glass transition temperature |
| GIC | = | thermal diffusivity |
| Al2O3 | = | aluminum oxide |
| C | = | cohesive failure |
| CFRP | = | carbon fiber reinforced polymers |
| DIC | = | digital image correlation |
| DSC | = | differential scanning calorimetry |
| E´ | = | storage modulus |
| εx | = | failure strain in the x direction |
| Fe3O4 | = | iron oxide |
| GFRP | = | glass fiber reinforced polymer |
| h | = | height |
| P | = | applied load |
| Ra,2 | = | arithmetic mean height in the transverse direction |
| Sku | = | kurtosis |
| Sq | = | root mean square height |
| Sv | = | maximum height of valleys |
| SBT | = | Simple Beam Theory |
| σfail | = | failure strength |
| σYield | = | yield strength |
| TEPs | = | thermally expandable particles |
| TMA | = | thermo-mechanical analyzer |
Supplementary material
Supplemental data for this article can be accessed online at https://doi.org/10.1080/00218464.2023.2256670