Effects of meso‐ and micro‐scale defects on hygrothermal aging behavior of glass fiber reinforced composites.

Design and process‐induced defects in fiber‐reinforced polymers (FRPs) lead to fracture nucleation due to the stress concentrations. In addition to the degradation in mechanical properties, defects can accelerate aging of FRPs and limit their service life. Efforts to understand the impact of defects have largely focused on the mechanical performance of FRPs. However, their impact on aging performance has not yet been extensively investigated. Here, we report the effect of the meso‐scale (missing yarn) and micro‐scale (micro‐crack) defects on the hygrothermal aging behavior of FRPs. Missing yarn defects were generated by pulling‐out yarns in warp and weft directions of glass fabric. Then, micro‐cracks were induced in composite laminates by acoustic emission controlled tensile loading/unloading. After exposing samples to the hygrothermal aging, we found that meso‐scale defects deteriorate mechanical/thermomechanical performance, reaching 30% decrease in the flexural strength. Notably, even though increasing micro‐crack density reduces the moisture saturation time, the aging time is reported as a more predominant design parameter, deteriorating the mechanical performance for micro‐crack‐induced FRPs. [ABSTRACT FROM AUTHOR]