Ambient‐Temperature‐Stable Epoxy Prepregs With Tunable Processability and Curing Behavior: Correlating Prepreg Structure With Composite Performance

ABSTRACT A new one‐component epoxy resin comprising Araldite LY 1564, triethylenetetramine (TETA), and dicyandiamide was impregnated into twill carbon fiber fabric and partially cured at low temperature via selective reaction between TETA and DGEBA, producing ambient temperature‐stable prepregs. Systematic variation of TETA content enabled precise tuning of viscosity, glass transition temperature, drapability, and tackiness, revealing strong correlations among these properties. A practical drapability test with a coefficient of variation of 10% was developed and validated, demonstrating a direct link between prepreg drapability and interlaminar shear strength (ILSS) of the resulting composites. A critical viscosity–drapability threshold, 20% of degree of cure, was identified, beyond which ILSS sharply declined, above 8% with respect to an increase of 5% of degree of cure, highlighting that early‐stage resin behavior governs final composite performance. These findings establish a structure–property–performance framework for dual‐cure epoxy prepregs, providing a simple predictive tool for assessing prepreg quality and guiding the design of advanced systems for high‐performance aerospace, automotive, and industrial applications.