In advanced engineering applications such as aerospace

petrochemical

and rail transportation

bolted joints often operate under complex service conditions involving high temperatures

high pressures

and multi-source coupled loads. Piezoresistive sensors exhibit strong potential for engineering applications owing to their mature fabrication process

low cost

and sensitive response characteristics. In this study

a piezoresistive sensor featuring high-temperature resistance

high integration

and a wide response range was developed. A conductive solution was prepared by mechanically stirring and ultrasonically dispersing carbon black (CB)

aluminum oxide (Al

2

O

3

)

and polyamic acid (PAA) solution. The sensor

with a thickness of 100 μm

was fabricated using blade coating followed by thermal imidization

and subsequently integrated with a flexible printed circuit (FPC). Experimental results show that the sensor can operate stably at 300 ℃ for extended periods. In monitoring tests of M20 large-size bolted joints looseness

the sensor demonstrated a torque measurement range of up to 100 N·m and a pressure range of 34.30 MPa. The experimental results verify its stable monitoring performance under high-temperature and high-load conditions

offering a robust technical solution for the identification of loosening states in large-scale bolted joint structures of critical engineering equipment and demonstrating significant potential for practical engineering applications.