Electrical Resistance Change of Unidirectional CFRP Due to Applied Load

Carbon Fiber Reinforced Plastic (CFRP) is composed of electric conductive carbon fibers and electric insulator resin. Self-monitoring system has been reported utilizing electric resistance change of unidirectional CFRP due to fiber breakages and to applied strain. Piezoresistivity is electric resistance change with applied strain. Many researchers have already reported the piezoresistivity of unidirectional CFRP. There is, however, large discrepancy in the measured piezoresistivity even in the fiber direction during tensile loading: both positive piezoresistivity (electric resistance increase) and negative piezoresistivity (electric resistance decrease) are reported during tensile tests. Electric resistance change at electrodes due to poor electric contacts are reported to be a main cause of this large discrepancy. In the present study, therefore, basic properties of piezoresistivity were measured with specimens made from single-ply and multi-ply laminates using a four-prove method. Many cases of electric resistance changes in the fiber direction transverse direction were measured during tensile loading. Effect of shear loading was also investigated using a shear test. To investigate the effect of poor electric contact at the electrodes, electrodes were made without polishing specimen surface and a tensile test was performed with measuring piezoresistivity. After the test, the specimen surface was polished, and a tensile test was performed again using the identical specimen. As a result, positive piezoresistivity was obtained for both single-ply and multi-ply specimens and negative piezoresistivity is confirmed that it was caused by the poor electric contact at electrodes.

[1]  K. Schulte Sensing with Carbon Fibers in Polymer Composites , 2003 .

[2]  D.D.L. Chung,et al.  Continuous carbon fibre epoxy-matrix composite as a sensor of its own strain , 1996 .

[3]  Karl Schulte,et al.  Load and failure analyses of CFRP laminates by means of electrical resistivity measurements , 1989 .

[4]  D.D.L. Chung,et al.  Structural health monitoring by electrical resistance measurement , 2001 .

[5]  Akira Todoroki,et al.  Delamination identification of cross-ply graphite/epoxy composite beams using electric resistance change method , 2002 .

[6]  D.D.L. Chung,et al.  Piezoresistivity in continuous carbon fiber polymer‐matrix composite , 2000 .

[7]  A. Chateauminois,et al.  In situ detection of damage in CFRP laminates by electrical resistance measurements , 1999 .

[8]  D.D.L. Chung,et al.  Strain sensing using carbon fiber , 1999 .

[9]  Phil E. Irving,et al.  Fatigue damage characterization in carbon fibre composite materials using an electrical potential technique , 1998 .

[10]  S. Al-Hassani,et al.  ELECTRICAL RESISTANCE MEASUREMENT TECHNIQUE FOR DETECTING FAILURE IN CFRP MATERIALS AT HIGH STRAIN RATES , 1994 .

[11]  G. Giraud,et al.  In-situ monitoring of damage in CFRP laminates by means of AC and DC measurements , 2001 .

[12]  D.D.L. Chung,et al.  Real-time monitoring of fatigue damage and dynamic strain in carbon fiber polymer-matrix composite by electrical resistance measurement , 1997 .

[13]  D. Chung,et al.  Mechanical damage and strain in carbon fiber thermoplastic‐matrix composite, sensed by electrical resistivity measurement , 2002 .

[14]  Akira Todoroki,et al.  Measurement of orthotropic electric conductance of CFRP laminates and analysis of the effect on delamination monitoring with an electric resistance change method , 2002 .

[15]  Hiroaki Yanagida,et al.  Preventing Fatal Fractures in Carbon‐Fiber–Glass‐Fiber‐Reinforced Plastic Composites by Monitoring Change in Electrical Resistance , 1993 .