Effects of piezoelectric ceramic volume fraction and composite thickness on the electromechanical impedance spectra of 1–3 cement-based piezoelectric composites

• Systematic study of PZT fraction and thickness effects on 1-3 CBPCs. • Resonant frequencies show a distinct U-shaped trend with increasing PZT fraction. • Electromechanical coupling coefficient ( k ₜ) increases with both PZT fraction and thickness. • Mechanical quality factor ( Q ₘ) peaks at ∼35.6% PZT and decreases with thickness. • Response surface models enable tailored composite design for specific SHM applications. This study systematically investigates the effects of PZT volume fraction ( P vf ) and composite thickness ( C t ) on the electromechanical impedance spectra of 1-3 cement-based piezoelectric composites (1-3 CBPCs), which are promising candidates for embedded structural health monitoring (SHM) sensors in civil infrastructure. A series of 1-3 CBPCs with P vf of 29.4%, 35.6%, and 41.3%, and C t ranging from 1.0 to 5.0 mm were fabricated using a precision cutting-and-filling technique. The impedance spectra were characterized to determine the resonant ( f r ) and anti-resonant ( f a ) frequencies, electromechanical coupling coefficient ( k t ), and mechanical quality factor ( Q m ). Results reveal that f r and f a exhibit complex, non-monotonic trends with P vf and C t , influenced by competing effects of effective stiffness, density, and pillar aspect ratio. The k t value increases significantly with both increasing P vf and C t , attributed to enhanced piezoelectric activity and reduced lateral clamping, respectively. In contrast, Q m peaks at an intermediate P vf of 35.6% and decreases with increasing C t , indicating a trade-off between energy conversion efficiency and mechanical damping. Response surface models were developed to quantify the synergistic effects of P vf and C t on these parameters. The findings provide critical guidelines for the tailored design of 1-3 CBPCs, enabling optimization for specific SHM application requirements such as high sensitivity (prioritizing high k t ) or high frequency resolution (prioritizing high Q m ).