Biodegradation and debonding detection of composite-wrapped wood structures

In this article, a methodology is presented for detecting biodegradation and debonding damage in composite-wrapped wood structures using a coplanar capacitance sensor. The presence of damage in the composite/wood interface alters the dielectric characteristics, causing a variation in the measured capacitance by the sensor. The theoretical background employed in developing the proposed capacitance technique is highlighted. A glass fiber reinforced polymers (GFRP)-wrapped wood column, containing pre-induced defects to simulate biodegradation damage and debonding of the GFRP at the composite/wood interface, was constructed and inspected in a laboratory setting. A coplanar capacitance sensor was designed and used for the inspection of simulated defects of different severity. The capacitance signals were measured and the sensor sensitivity was evaluated for each defect type. The proposed technique can be used for rapid damage screening, scheduled or random inspection, or as permanent sensor network within the composite/wood system as a structural health monitoring technique.