Study on Creep Mechanical Properties of HTPB Solid Propellant

Area of Science:

• Materials Science
• Aerospace Engineering
• Solid Rocket Propellant Mechanics

Background:

• Hydroxyl-terminated polybutadiene (HTPB) is a key binder and fuel matrix in solid rocket propellants.
• Exposure to mechanical loads and environmental variations can cause time-dependent creep deformation in these energetic materials.
• Creep deformation can negatively impact rocket motor performance by altering grain geometry, affecting combustion stability, and reducing structural reliability.

Purpose of the Study:

• To experimentally characterize the creep behavior of HTPB-based solid propellants under tensile stress at room temperature.
• To develop and validate a constitutive model capable of accurately describing the strain-time response of HTPB propellants during creep.
• To provide a foundation for improved creep deformation assessment, formulation optimization, and structural reliability analysis of HTPB-based propellants.

Main Methods:

• Room-temperature tensile creep tests were performed on HTPB-based solid propellant samples at various stress levels.
• Viscoelastic and power-law constitutive models were evaluated to determine the best fit for the experimental data.
• A composite time-hardening creep model was developed and implemented in Abaqus finite element analysis (FEA) software using a Fortran user subroutine.

Main Results:

• Experimental data from tensile creep tests provided insights into the time-dependent inelastic deformation of HTPB propellants.
• The developed composite time-hardening creep model effectively captured the observed strain-time response of the propellant.
• Successful implementation of the model in Abaqus enables finite element simulations for predicting creep behavior.

Conclusions:

• The established composite time-hardening creep model offers an accurate representation of HTPB propellant creep deformation.
• This research provides essential data and a validated model for assessing the structural integrity and performance of HTPB-based rocket motors.
• The findings support advancements in propellant formulation and enhance the structural reliability analysis of aerospace propulsion systems.