Test setup for scanning laser thermography: Simultaneous detection of internal delamination and surface cracks in a single continuous inspection step.
Source: BAM
Fiber-reinforced plastics are among the key materials used in modern lightweight construction. In the aerospace industry, as well as in automotive manufacturing and wind energy, they enable significant weight savings while maintaining high load-bearing capacity. However, the material has a treacherous property: impacts and collisions, such as those occurring during handling or from external impacts (hail, falling rocks, etc.), can cause severe damage inside the component without leaving a visible dent on the surface. Such barely visible impact damage can significantly reduce a component’s compressive strength and is often critical to safety.
In collaboration with AGH University of Science and Technology in Krakow, a testing method has now been developed that reliably detects the characteristic damage features of impact damage—internal delamination and near-surface cracks in the matrix—in a single testing step. This is based on non-destructive testing using active laser thermography: Here, a laser beam is expanded into a narrow line and guided precisely over the component by a robotic arm. A high-resolution thermal imaging camera records how the heat introduced by the laser beam propagates through the material. Defects disrupt this heat flow and generate measurable temperature differences on the surface.
The methodological core of the study lies in the two-pronged analysis of the recorded thermal image sequences. The first analysis path reconstructs the complete temporal temperature profile of each surface point, revealing underlying disturbances in the heat flow. The second path calculates the spatial temperature gradient along the scanning direction from each individual thermal image and sums these gradients over the entire measurement period. The resulting image highlights sharp temperature jumps at surface cracks against the background noise. Both result images can then be merged into a combined false-color image in which delaminations and cracks are simultaneously and spatially uniquely identified.
Since scanning active laser thermography is infinitely scalable in terms of area and can be fully integrated into robot-assisted inspection systems, the method opens up a practical path to automated inspection and condition monitoring of large composite structures.
Impact damage characterization on CFRP parts using laser line scanning active thermography
Michał Sobczak, Julien Lecompagnon, Philipp Daniel Hirsch, Łukasz Pieczonka, Mathias Ziegler
Composites Part B: Engineering, 2026