Predictions of Yield Strength Evolution Due to Physical Aging of 828 DGEBA/DEA using the Simplified Potential Energy Clock Model

Technical Report · Mon Feb 25 04:00:00 EST 2019

DOI:https://doi.org/10.2172/1498246· OSTI ID:1498246

Tenney, Craig M. ^[1]; Long, Kevin Nicholas ^[1]; Kropka, Jamie Michael ^[1]

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1. Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

The capability of the Simplified Potential Energy Clock Model (SPEC) to represent the uniaxial compression yield strength evolution under isothermal aging conditions is evaluated for a widely used epoxy thermoset encapsulation material, 828 DGEBA/DEA. A baseline model calibration is used. We note that this calibration did not consider yield strength behavior close to the glass transition temperature (T_g), but in this work, the model is exercised in this temperature range to evaluate the ability to predict changes in material response with aging as equilibrium is approached. Some model alterations were needed to remove negative Prony weights in the thermal and bulk relaxation function (f₁), which is chiefly responsible for aging in this analysis, but otherwise, the model was not altered. Model predictions of yield stress evolution are quantitatively different compared with experiments, but the rate of change of yield stress with respect to aging time is in reasonable agreement with respect to experiments for the first 1000 hours of aging. After this aging time, the measured yield stress stops evolving, but the model continues to evolve for several more decades in time. Parametric studies and model alterations are considered to investigate how yield strength evolution predictions are affected by modeling choices. It is clear that the baseline calibration must be re-examined in order to represent the aging data quantitatively.

• Research Organization: Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 1498246
• Report Number(s): SAND2019--2248R; 673013
• Country of Publication: United States
• Language: English

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