Debonding-on-demand adhesives for circular automotive manufacturing: Triggering mechanisms, joint performance, and process integration - A systematic review

Adhesive bonding is a critical enabling technology for lightweight multi-material automotive structures combining steel, aluminium, carbon fibre reinforced polymers (CFRP), and thermoplastics. However, conventional structural adhesives are permanent by design, creating a fundamental conflict with end-of-life recyclability targets that require vehicles to achieve 85% recyclability and 95% recoverability by mass and EV battery packs to use joining methods compatible with disassembly. Debonding-on-demand (DoD) adhesives—systems that maintain structural performance in service but release controllably upon application of an external stimulus— represent a promising reso-lution to this conflict. This paper presents a systematic review of the DoD adhesive literature. Although the literature search spanned 2000–2025 to capture foundational work, the field is recent and the majority of quantitative studies benchmarked here were published between 2019 and 2025; the review therefore emphasises this period while retaining seminal earlier references. Four stimulus categories are covered: thermal (Diels–Alder reversible networks, thermally expandable particles, and vitrimer/covalent adaptable networks), electrical, photothermal/UV, and magnetic/hybrid. Quantitative performance data from over 40 primary studies are benchmarked against automotive lap-shear, fatigue, and crash-stability requirements. Process integration challenges—including paint-shop cure compatibility, trigger de-livery in assembled structures, surface preparation, scalability, and supply-chain incentive alignment—are critically assessed. Key findings are: (i) TEP-modified structural adhesives achieve debonding at 120–175 °C via electromagnetic induction while maintaining 20–25 MPa pre-debond lap-shear strength on CFRP/Al/steel substrates; (ii) Diels–Alder epoxy systems now reach competitive lap-shear strengths of 12–16 MPa with debonding at 140 °C, whilst vitrimer adhesives provide an emerging route to recyclable structural bonding; (iii) the split-incentive problem is the dominant systemic barrier to adoption; and (iv) no standardised DoD test protocol, long-term durability data, or comprehensive life-cycle assessment currently exists. Five research gaps define the agenda for future work.