Elastic Memory Composite Microbuckling Mechanics: Closed-Form Model with Empirical Correlation

Abstract

Elastic memory composite (EMC) materials are space-qualified, high-performance, shape-memory-polymer-based composites for use in constructing deployable space structures. EMC materials can be designed to exhibit significantly higher packaging strains than conventional composites through extensive elastic microbuckling of the fiber reinforcement at elevated-temperatures, when the shape-memory-polymer matrix is sufficiently compliant. Herein, we present a novel set of closed-form post-microbuckled mechanics-based solutions that quantify the wavelength and amplitude of fiber microbuckles within uni-directional EMC materials during elevated-temperature bending when the matrix is very compliant. This effort is unique from previously published fiber- microbuckling work in that it focuses on post-microbuckled behavior whereas the existing literature focuses on the initiation of microbuckling, it accounts for essential kinematic constraints on EMC microbuckling behavior that have not been previously captured, and composite properties that can be measured experimentally are used to formulate the model whereas micromechanics calculations based on constituent level properties are imbedded within the majority of the existing models. Correlation of the model with a set of EMC empirical studies is also done. This model provides a proper foundation for predicting other highly nonlinear mechanical behavior in EMC materials, like the applied-moment versus induced-curvature response, which are beyond the scope of the present study.