Center for Composite Materials - University of Delaware

Research Summary

Understanding Fracture Toughness Behavior in Compliant Adhesives with Non-Trivial Bondline Thicknesses

Authors: M. Wang (MS-MSE), R. Jensen (ARL), J. Gillespie (CCM)

Introduction/Objective

Objective: This work will focus on understanding the thickness effects on mode I fracture toughness of compliant adhesives for use in damage tolerant applications
• Do not agree well with traditional linear elastic fracture mechanics (LEFM)
• Apply non-linear fracture mechanics (NLFM) in the form of the J-integral
• Derive the mode I traction laws to gain a more fundamental understanding of the fracture behavior of compliant adhesives

Materials Survey

Materials:
• Applied Poleramic Inc. (API) SC-12TX epoxy adhesive
• Cytec FM-94 film epoxy adhesive
• WeldOn SS340 methacrylate adhesive
• Air Products Versalink C-100 Army Research Lab (ARL) blend polyurethane adhesive
• Polymeric state/ glass transition (Tg) as measured by a Thermal Advantage (TA) Discovery Series DSC

Tensile Characterization

• ASTM D412
• Die A & C Dog-bone coupons
• Constrain strain rate of 1.412x10^-3 unit/s
• Performed on Instron 5567

Digital Image Correlation (DIC) System Overview

Correlated Solutions:
• Non-contact shape and deformation measurement system

J-Integral Measurement via DIC

Future Testing

• Complete DCB Testing
• Multiple Bond-thickness
• Generate R-curves
• Derive traction laws
• Evaluate bondline thickness effets
• Correlate results with Mode II fracture toughness.

Acknowledgements

This work is supported by the Army Research Laboratory (ARL) through a cooperative agreement (W911NF-08-2-0062) with Air Products and Chemicals, Inc. and UD-CCM.

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