Real time in situ multi-axial strain monitoring by capacitive strain gauge

Problem Definition:

Polymer Matrix Composites have gained their popularities over traditional heavy metal materials since they are mechanically strong enough, yet light-weighted and resistant to harsh environment. Typical applications (Fig. 1) include construction, wind energy, automotive, and aerospace products. In these high-end applications, conservative design approaches are usually applied to keep the strain levels sufficiently low and to prevent crack propagation. This leads to a few issues such as: more manufacturing materials, higher energy consumption during production/operation due to higher weight of the product, costly manual inspection under severe environmental conditions.

Fig.1:typical applications of composites


For the master thesis, the student will develop a continuous strain monitoring system for real time in situ multi-axial strain monitoring of composites. The key component of the system is a strain gauge (Fig. 2), which changes its electrical properties (e.g. capacitance, resistance) under tension/compression. 

Fig.2: working principle of a resistive strain gauge

The strain gauge will be embedded/attached to the composite structure, the change of its electrical properties will be monitored in real time. The measured electrical signal can then infer the change of strain distribution in  the structure. The foreseen work includes:

-        Study/design/fabricate a capacitive strain gauge.

-        Experiment and characterize the sensor with different materials

-        Compare capacitive strain gauge with resistive strain gauge

-        Implement a sensor node for multi-axial strain measurement

-        Extend single node to a network of nodes

-        Design/implement a readout circuit to the sensor network

-        (Optionally) Software on PC for visualization


strain monitoring; capacitive strain gauge; sensor fabrication; PCB design; microcontroller;


Ardoyen CMST.