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Large-Area Additive Manufacturing (LAAM) has seen increased application in manufacturing meter-scale, polymeric composite structural parts, especially for tooling and fixturing. Unfortunately, LAAM introduces manufacturing-induced defects in printed composites, e.g., intrabead microvoids and poor interbead adhesion that are not otherwise seen when traditional manufacturing methods are used, causing degradation of mechanical and fracture properties. In this paper, the fracture behavior of neat acrylonitrile butadiene styrene (ABS) and short carbon fiber-reinforced ABS (CF/ABS) fabricated by LAAM is compared and analyzed by evaluating their energy release rate 𝐺𝐼𝑐 and fracture mechanisms. A double cantilever beam with doublers (DCB-D) test for single-bead, double-bead, and multiple-bead configurations is developed by incorporating rigid doublers to reduce the compressive failure at the crack tip, allowing for the measurement of crack propagation. A new data reduction method for these configurations is derived to remove the doubler effect from the 𝐺𝐼𝑐 calculation, producing ‘pure’ intrabead and interbead 𝐺𝐼𝑐 values. We show that CF/ABS is more damage tolerant than ABS at the intrabead level, but less damage tolerant than ABS at the interbead level. The development of plastic ligaments in ABS helps dissipate additional strain energy, improving the overall energy release rate. The experimental fracture test approach developed here is expected to provide mechanistic insight into their damage tolerance capability, accelerating the qualification process of LAAM-produced polymer and polymer composites. 

This paper proposes an efficient experimental method to measure the mode I fracture toughness of large-area additive manufactured polymeric composites. By utilizing either single-bead or double-bead systems bonded to the double cantilever beam (DCB) configuration, we measure intrabead and interbead fracture toughness of acrylonitrile butadiene styrene (ABS) and short carbon fiber-reinforced ABS. The effect of rigid doublers (which are used to eliminate a premature compressive failure) is excluded in the calculation of total energy dissipation, producing a purely interlayer fracture toughness. We found that the critical fracture toughness of carbon fiber/ABS is lower than that of ABS due to the voids within and between the beads. The experimental and data reduction methods developed here can be utilized to optimize the interlayer adhesion of large-scale 3D printed materials.