Conclusions
In the present work, the stiffness reduction of a quasi-isotropic CFRP laminate obtained by automated fibre placement innovative process was studied by means of a thermographic approach.
A total of ten specimens were tested at four different stress levels, 50-60-65-70% of UTS, and monitored by using infrared thermal camera.
The analysis of thermal signal provided the thermoelastic signal used as metrics for evaluating stiffness degradation. At the same cycles-to-total cycles ratio, thermoelastic data were compared to the data of the extensometer that provided averaged stress/strain data in the gage length of the sample.
Specific processing algorithms were used to extract the mechanical and thermal metrics.
The major outcome of the present research is represented by the modelling of the stiffness degradation by using thermoelastic data.
The other results achieved by performing present research are:
This approach is useful also because it can be adopted to estimate stiffness degradation on in-situ applications on operating components where stress state and damage behaviour are unknown and where the extensometer cannot be used.