Contact between traps and surfaces during contact sampling of explosives in security settings

Area of Science:

• Materials Science
• Surface Science
• Tribology

Background:

• Realistic modeling of interfacial contact between rough, deformable surfaces is challenging but critical for applications like explosives detection.
• Understanding how material properties influence contact mechanics is essential for optimizing surface sampling and cleaning.

Purpose of the Study:

• To experimentally and computationally investigate the interfacial contact between common traps and surfaces used in explosives detection.
• To develop a more realistic model of trap-surface interactions by combining microcontact and macro-scale material behavior.
• To guide the development of improved trap materials for surface sampling and cleaning applications.

Main Methods:

• Nanoindentation was used to measure the Young's modulus and hardness of four traps and seven substrates.
• The Oliver-Pharr method and an indenter area function (using silicon and gold) were employed for nanoindentation data analysis.
• Contact simulations combined the Greenwood-Williamson microcontact model for asperities and the Timoshenko Beam model for bulk trap materials.

Main Results:

• Young's moduli ranged from 0.2 to 8 GPa for traps and 0.5 to 4 GPa for surfaces.
• Hardness values ranged from 0.005 to 0.22 GPa for traps and 0.02 to 0.2 GPa for surfaces.
• The combined modeling approach provided a more realistic description of interfacial contact than individual models.

Conclusions:

• The study provides a novel method for estimating the relative effectiveness of traps in interrogating surface topography.
• The developed modeling approach can guide the selection and design of trap materials for enhanced explosives detection and surface sampling.
• Accurate characterization of material properties and contact mechanics is key to advancing airport security technologies.