MEMS-based surface mounted health monitoring system for composite laminates

Composite structures subjected to extreme loadings like, e.g. impacts, can undergo a reduction of their stiffness and strength properties, due to the nucleation and subsequent propagation of cracks along the interfaces between different phase materials. This phenomenon turns out to be difficult to detect through cheap monitoring procedures. Here, we discuss a methodology to monitor the state of crack-containing composite laminates through low-cost, commercial off-the-shelf MEMS accelerometers. By adopting cyclic loading conditions, we track the evolution of the cracked, or debonded region in a double-cantilever beam; this is achieved by surface mounting a MEMS (along with its board) and by monitoring the drift in the compliance of the specimen induced by crack growth. The methodology is validated through an analytical model of the experimental test, which highlights the sensitivity of the monitoring scheme to the crack length.