Quantitative analysis of crack patterns in coatings.

Area of Science:

• Materials Science
• Physics of fracture
• Thin film mechanics

Background:

• Crack networks in thin films typically form sequentially.
• Experimental observations often show disconnected patterns, deviating from ideal models.
• Understanding the transition to connected networks is crucial for material design.

Purpose of the Study:

• Investigate the physical origins of the transition between disconnected and connected crack networks.
• Link crack network connectivity to the mechanical response of thin films.
• Quantify the influence of film thickness on fracture dynamics.

Main Methods:

• Quantified crack network connectivity using morphological descriptors.
• Performed controlled experiments on thin film coatings.
• Developed a unified energetic framework to interpret results.

Main Results:

• Film thickness critically influences fracture dynamics.
• Thin films exhibit simultaneous cracking, leading to disconnected networks.
• Thicker films display sequential fracture, resulting in highly connected networks.

Conclusions:

• A dimensionless parameter comparing elastic and fracture energies governs the transition between cracking regimes.
• Film thickness is a key factor determining crack network connectivity.
• The study provides a unified energetic framework for understanding fracture patterns in thin films.