A Nondestructive Study of a Carbon Fibre Epoxy Composite Plate Using Lock-In Thermography, Cyclic Loading, and Finite Element Analysis

The goal of this study was to validate the results from infrared thermographic experiment by strain gauge experiments and finite element analysis (FEA) in a carbon epoxy composite plate within the linear elastic limit. A FE model of the plate was first developed and subjected to static loads. The strain values were recorded at four distinct points. Then an experiment using strain gauges was carried out for similar loading conditions and the strains were noted for the corresponding locations. The slope of the correlation plot between the FEA and strain gauge static results indicated that, although the strain gauge experimental values had an overall tendency to overestimate the strain, there was a strong correlation between the data as exhibited by the Pearson coefficient R² = 0.99. Then the stresses calculated from the strain gauge experiment under cyclic tensile loads were used to validate the results from lock-in thermography. These results also showed good agreement as R² was 0.87 and strain gauges experiement tended to underestimate the stress values. From this study, it can be concluded that lock-in thermography can be used to assess stresses in biomaterials used in medical application.