Development of a Test Bench for the Investigation of Thermoplastic-Thermoset Material Combinations in Additive Manufacturing

Abstract

To enhance the mechanical properties of fused filament fabricated parts, the process integrates continuous fibers. Currently, fibers are impregnated either with thermoplastics or with thermoset material, which is completely cured before printing and later combined with thermoplastic filament during the coextrusion process. A major problem about using cured thermoset matrix for the fibers is an insufficient bond between the fiber matrix and the thermoplastic material. A new approach proposed by the authors combine uncured thermoset matrices with thermoplastic filaments to form a substance-to-substance bond. To investigate the material and bonding behavior, a test bench is constructed. Its main purpose is to replicate the coextrusion of thermoplastic filament and thermoset impregnated continuous fibers. Parameters, such as temperature, tension and extrusion speed can be adjusted within the setup to accurately simulate the additive manufacturing process. Aluminum blocks including heater cartridges and thermocouples act as hot ends and impregnation units. Heated blocks compact the fiber strands. We tested different heating blocks containing flat and curved geometries including actual additive manufacturing nozzles to evaluate the impregnation behavior of the dry carbon fiber filaments. Approaches with additive manufacturing nozzles show the most promising results regarding fiber impregnation with thermoplastic material.