Crack path engineering using viscoelastic target layers for enhanced damage tolerance in multilayer rubber composites

Interfacial cracking in multilayer viscoelastic composites often leads to sudden structural failure, yet conventional strategies focus mainly on strengthening interfaces rather than controlling crack trajectory. This study introduces a viscoelastic crack-path engineering approach that deliberately redirects unstable interfacial cracks into a compliant target layer, converting catastrophic interfacial delamination into stable cohesive damage. Three target-layer compounds with identical hardness but varied fracture resistance (Gc), and energy release rate (G), Weak (Gc/G ≈ 1 J/m2), Semi-Strong (Gc/G ≈ 2.5 J/m2), and Strong (Gc/G ≈ 2.85 J/m2) were designed to provide systematic change for crack path selection. The toughest compound benefited from a combination of high viscoelastic dissipation and strain-induced crystallization capability. A two-tier predictive criterion, based on the ratios Gtarget/Gply and Gc,target/Gc ,ply (1.74–4.42), was formulated to quantify primary crack deflection tendencies and secondary path selection. Peel tests on two-layer laminates validated the model: the Weak compound consistently directed cracks into the target layer whereas the Semi-Strong and Strong formulations displayed interface-dominated or alternating failure modes. Finally, full-scale motorcycle tire endurance and high-speed testing confirmed the scalability and engineering relevance of the proposed design methodology.