Stiffness distribution in insect cuticle: a continuous or a discontinuous profile?

Area of Science:

• * Biomechanics
• * Materials Science
• * Entomology

Background:

• * Insect cuticle is a complex biological composite with intricate architecture and material composition.
• * Interpreting nanoindentation data from insect cuticle is challenging due to its layered structure.
• * Understanding stiffness variations through cuticle thickness is crucial for accurate biomechanical modeling.

Purpose of the Study:

• * To numerically investigate stiffness variations within insect cuticle using finite-element (FE) models.
• * To develop more accurate FE models for analyzing insect cuticle biomechanics.
• * To provide guidelines for improving nanoindentation testing and data interpretation.

Main Methods:

• * Mathematical description of continuous and discontinuous stiffness profiles through cuticle thickness.
• * Development of FE models based on cuticle structures of three insect species.
• * Simulation of nanoindentation experiments on these FE models.

Main Results:

• * FE models incorporating discontinuous exponential stiffness gradients accurately predicted stress and deformation.
• * A revised indentation depth to cuticle thickness ratio of 7% is proposed for enhanced accuracy.
• * The study highlights the importance of material distribution in insect cuticle mechanics.

Conclusions:

• * Discontinuous stiffness gradients are key to accurately modeling insect cuticle.
• * Refining the '10% rule' for nanoindentation improves data reliability.
• * This research provides a foundation for more realistic modeling of insect cuticle composites.