Mechanical Response of a Macro-Fibre Composite-Bonded Cantilever Beam and Its Sandwich Configuration for Low-Intrusion Deformation Suppression

Macro-fibre composite (MFC) actuators offer improved flexibility and damage tolerance over monolithic piezoceramics, which have been widely utilised recently. However, direct bonding to a heritage substrate of MFC actuators may cause local stress concentration and complicate removal. To overcome this, a protective aluminium–concrete sandwich configuration is proposed, where the MFC patch is attached to a replaceable thin aluminium carrier layer that transfers a controlled deformation field to the concrete substrate through the bonded aluminium–concrete interface, enabling reversible, low-intrusion deformation control without direct modification of the protected substrate. A coupled electromechanical finite-element formulation is derived from the linear piezoelectric constitutive equations and Hamilton’s principle. The model is first is validated against benchmark deflection and modal data for a traditional MFC-bonded aluminium beam, achieving a maximum deflection error below 1% (0.9142 mm vs. 0.9141 mm at the free end) and excellent frequency agreement (19.7 Hz and 112.0 Hz). Laboratory cantilever tests under 400 V show a systematic amplitude reduction relative to the perfect-bond model: the measured free-end displacement is approximately 0.598 mm compared with 0.9142 mm numerically. A one-parameter effective actuation-transfer coefficient of 0.656 reduces the displacement-profile RMSE to 0.0072 mm (NRMSE 1.23%, R2 = 0.9987), indicating that the dominant discrepancy is an amplitude loss associated with non-ideal strain transfer and boundary/electric-field effects rather than a change in deformation mode. For the proposed sandwich beam, simulations reveal a monotonic, voltage-dependent response: tip deflection rises from approximately 0.03 mm at 200 V to 0.115 mm at 800 V over a 200 mm span. Actuator placement near the fixed end yields higher bending authority, consistent with classical placement theory. The sandwich concept demonstrates that a replaceable protective layer can generate controllable curvature while maintaining moderate stress levels in the protected substrate, making it suitable for micro-crack suppression and temporary stabilisation of fragile components such as cultural relics or aged concrete. The validated model provides a foundation for future experimental calibration and distributed actuator optimisation.