A Manufacturing Process Simulation of Toughened Cyanate-Ester-Based Composite Structures with Respect to Stress...

Area of Science:

• Materials Science
• Mechanical Engineering
• Aerospace Engineering

Background:

• Cyanate-ester composites are vital for high-temperature aerospace applications.
• High curing temperatures (up to 260°C) induce significant process-induced stresses.
• Understanding stress relaxation is key to managing residual stresses in these materials.

Purpose of the Study:

• To experimentally determine the stress relaxation effects in a cyanate-ester composite.
• To derive and integrate constitutive equations into finite element analysis (FEM) software.
• To apply this integrated approach to analyze residual stress formation in a stiffened aerospace panel.

Main Methods:

• Developed a toughened cyanate-ester composite for high-temperature use.
• Measured and characterized the stress relaxation behavior of the neat resin.
• Integrated an incremental linear viscoelastic model into a process model.
• Validated the model using a manufactured stiffened panel and an optical 3D measuring system.

Main Results:

• Stress relaxation effects increased closer to the toughener's glass transition temperature (~240°C).
• Simulated and experimental displacement fields showed good agreement, with a maximum difference of 15% between elastic and viscoelastic solutions.
• Transverse material stresses were found to exceed material strength, indicating a critical failure risk.

Conclusions:

• The developed viscoelastic model accurately predicts residual stress in cyanate-ester composite structures.
• The study highlights the critical importance of accounting for stress relaxation in composite manufacturing.
• Findings provide crucial data for designing robust high-temperature aerospace components.