Prediction of Residual Stresses in a Thick Composite Rim After Manufacturing and Curing
Residual stresses induced during the manufacturing and curing of thick fiber-reinforced thermoset composite components may impact performance and can lead to premature component failure. The objective of this study is to predict the residual stresses in a filament-wound composite rotor manufactured for a flywheel energy storage system (FESS). Previous research on residual stresses in thick composite cylinders only considered one-directional heat flow. For short cylinders like the rims used for the FESS the heat flow in longitudinal direction cannot be neglected. A model was developed in the Matlab technical computing environment. The model was divided into three modules. Winding stresses and the fiber volume fraction variation were computed in the first step and used to calculate the mechanical and thermal properties for each element in a discretized rim. These properties along with a finite difference model were then used in the second module to simulate the two-dimensional heat flow and thermoset curing. In the final module, the stress state in the composite rim was calculated using a static finite element analysis. The present paper describes the modeling approach and an example case involving a glass-fiber epoxy composite rim. The numerical modeling approach, which considers the temperature loads, resin shrinkage, winding stresses and mandrel deformation, allows predicting the residual stresses occurring in a thick composite cylinder with finite length, and hence, contributes to the safe design of FESS rotor rims. The model may also serve as the basis for optimizing manufacturing processes in order to achieve higher performing composite parts.
Authors: Patrick Langheim, Pierre Mertiny
Conference: CAMX 2016 – Anaheim