A Multiphysics Model of Synergistic Environmental Exposure-Assisted Damage of Composite Using Homogenization-Based Degradation Variables

The adoption of fossil-based hydrocarbon polymer composites has been successful in both the automotive and aircraft industries and is rapidly expanding into buildings and civil infrastructure. One challenge to broader adoption of polymer composites in buildings and civil infrastructure is a limited ability to model the synergistic effects of the combined physical/chemical processes of environmental exposure and mechanical loading. Unlike other building materials, long-term experience and field performance data of polymer composites in buildings and civil infrastructure applications do not exist. The first and largest composite building system used in a high-rise exterior in the USA is the facade of the San Francisco Museum of Modern Art (SFMOMA) completed in 2015. Since historical, experience-based service life models for composite building applications are not available, it is crucial to build multi-physical-based models in order to predict composite service life performance on a semi-centennial or centennial time scale. This study is to build a physics-based model to predict synergistic effect of environmental exposure to damage of the composite. Based on the authors’ previous UV/moisture exposure experiment-computational study, this extended study couples degradation-induced material weakening to continuum damage model. Results of this study indicate that the synergistic effect of combined UV and moisture exposure on composite material degradation is more severe than simple linear superposition of each exposure’s damage. A comparison and analysis of UV and moisture exposure degradation mechanisms indicate that these environmental exposures caused material degradation by weakening the polymer matrix, along with weakening the interface between the polymer matrix and fiber reinforcing yarns. Moreover, the interface weakening is more critical than the former one.