Initial and adhesive contact between a diamond indenter and polydimethylsiloxane

Area of Science:

• Materials Science
• Surface Science
• Polymer Physics

Background:

• Understanding the initial contact mechanics of soft polymers like polydimethylsiloxane (PDMS) is crucial for applications.
• Adhesive contact and elastic deformation significantly influence material property measurements.

Purpose of the Study:

• To investigate the initial and adhesive contact behavior of PDMS with sharp indenters.
• To develop a method for accurate Young's modulus determination by correcting for initial penetration depth.

Main Methods:

• Detailed observation of load-depth data during indentation experiments.
• Application of a power-law relationship to model the initial loading curve.
• Utilizing an axisymmetrical indenter model with a sticky boundary condition.

Main Results:

• Load-depth results indicated nearly reversible behavior, characteristic of elastic deformation.
• Significant initial penetration depths were observed during surface finding.
• A linear relationship between load and depth was observed beyond a specific load threshold.

Conclusions:

• The study proposes a method to correct for initial penetration depth in indentation tests.
• Accurate and unique Young's modulus values for PDMS were obtained across different indenter geometries and environments.
• The sticky indenter model effectively explains the observed linear load-depth behavior.