About the Spring-In Phenomenon: Quantifying the Effects of Thermal Expansion and Chemical Shrinkage

Abstract

A straightforward approach to predict spring-in deformations of angled composite parts is presented. Therefore, a proposal by Radford is extended in order to calculate the spring-in contribution due to chemical shrinkage. For this, the volumetric shrinkage of neat thermoset resin, which is in the range of 2–7%, is transferred to equivalent strains on ply level assuming no shrinkage in fiber direction. As the fiber volume fraction (FVF) affects mechanical and chemical properties significantly, the spring-in angle is affected as well. Therefore, the numerical investigation accounts for the spring in angle and its thermal and chemical contributions depending on the FVF. Classical laminate theory (CLT) is utilized to homogenize layup expansion and shrinkage properties. For validation purposes, model predictions are compared with measurement results gained from one manufactured test specimen. Good agreement between analytical and experimental results is found. Furthermore, the chemical contribution of the total springin angle Du turned out to be significantly larger than the thermal contribution.