Dynamic Fracture of Thermosetting Resin System for Additive Manufacturing of Advanced Composites Using Digital Light Processing

This study examines the dynamic fracture behavior of high-performance thermosetting polymers for additive manufacturing (AM) to enable rapid production of lightweight and functional polymeric and composite materials that meet military requirements. We present a systematic investigation of the role of print orientation on the dynamic fracture response of a bis-GMA based AM polymer as a model material, using single edge notched tension (SENT) geometry. While most fracture criteria in predictive simulations use quasi-static values, fracture is innately dynamic and impulsively loaded cracks can have toughness values that differ by more than 20%. A unique long-bar striker apparatus is used to fire a striker at the opposite end of the notched and pre-cracked specimens in order to create a dominantly dynamic Mode-I (opening) fracture load. Digital Image Correlation (DIC) is used in conjunction with ultra high-speed imaging to capture the evolving displacement, and hence strain fields ahead of the crack tip. The elastodynamic solution accounting for inertial effects and wave interactions is optimized using a least squares fit to extract the evolving critical stress intensity factor (SIF) leading to initiation. Preliminary findings suggest that under impulsive loading, the print orientation does slightly affect the overall dynamic fracture toughness of the material.