Micro-Scale Fatigue Damage Assessment of CFRP Laminates Using Lock-in Thermography

This study proposes a new micro-scale damage assessment method of laminated carbon fiber-reinforced plastics based on the thermal diffusivity measurement. This measurement was conducted by the laser-spot-periodic-heating method using lock-in thermography. Measured samples were subjected to the tension fatigue test at a relatively low load and high cycle. As a result, the thermal diffusivity showed a decreasing trend with an increase in the load cycles. It was shown that this method can detect the effect of the minute fatigue damage at a level that cannot be seen with a microscope.

Algorithms for thermal diffusivity measurement of heterogeneous 1D materials based on Infrared Microscopy Enhanced Angstrom Method

An infrared microscopy enhanced Angstrom method has been develpoed to measure the thermal diffusivity. Infrared microscopy technique can acquire temperatures of multiple points at one shot. Two algorithms for calculating thermal diffusivity were proposed and compared in practice. One is based on global temperature data and the other is based on local temperature data. The according calculated thermal diffusivities are denoted as α n G and α n L . Three 1D materials of different heterogeneity (Cu wire, Ni-Cu wire and PVA-CNT fiber) were measured on the experimental platform. The calculated α n G and α n L values show that for homogeneous material such as Cu, these two algorithms give similar results, while for heterogeneous ones (Ni-Cu and PVA-CNT), they come to be discrepant. The data fluctuation analysis of f n L zooms in the discrepancy and verifies that α n L is more sensitive to local property change and more competent in revealing heterogeneous properties.