Control how temperature changes in a model are handled during an analysis.
The composite materials stored in the Composite Material Database are defaulted to have a stress-free temperature of 0° in the system of units you specify unless it is specified that the thermal residual stresses should be included in the analysis (via the *CURE STRESS keyword in the HIN file). In this case, the stress-free temperature stored in the material file will be used. (The stress-free temperature can be added to the material file using Composite Material Manager). Any initial temperature specified via the TREF command (including the default value of 0°) is used to calculate the residual stresses present in each of the constituents and the composite due to the unmatched coefficients of thermal expansion between the fiber and matrix. For details on how the temperature changes imposed in a model affect how residual stresses are calculated, please refer to the Theory Manual.
It is also important to consider the particular values for the initial and final model temperatures as they are dependent on whether the thermal residual stresses are included. If they are included, the initial temperature value must be the actual initial temperature and the final temperature must be the actual final value. This is because Helius PFA calculates the ΔT from the stress-free temperature to the current temperature of the model. If the residual thermal stresses are not included, the initial temperature of the model should be 0° and the final temperature should be the ΔT between the temperature the material was characterized at and the final temperature. For a detailed example on the use of thermal residual stresses, refer to Example Problem 2.