Evaluation of Tensile Strength and Repeatability of 3D Printed Carbon Fiber Materials and Processes

As additive manufacturing (AM) with composite materials becomes more widely used in industry to create high-strength components, it is vital to have quantified material properties that provide designers and engineers accurate data to decide which materials are suitable for their applications. This study replicates the build processes and tensile tests undertaken by AM material manufacturers to compare tensile strengths achieved with those stated on the manufacturers' data sheets. These are important data to research and analyze as either it will corroborate properties given by the manufacturers and provide confidence in the values provided or it will show that the manufacturer's values cannot always be achieved and that designers and engineers must be more critical about the values manufacturers are providing when using the materials in their own applications. Tensile tests were performed on additively manufactured specimens that had been built using the same parameters that were used during the manufacturers' testing procedures. Digital image correlation was used to accurately measure strain in the test samples, enabling material properties to be determined. Microscopy analysis enabled the visual inspection of the print quality, the identification of defects, and the determination of volume fraction with the samples. The results show inconsistencies between the tensile strength results achieved during this study and the tensile strengths stated by the manufacturers. The results show that two materials exceeded the expected values and one material did not reach the expected value. Analysis of the 3D printed specimens shows that poor fiber-matrix wetting, large voids, and weak interfacial bonding were accountable for the lower-than-expected tensile strength results. While good print quality, low void percentage, proper fiber-matrix wetting, and good control measures were accountable for results that exceeded expectation. These results show that designers and engineers cannot solely rely on material data sheets to establish the mechanical properties of their 3D printed components.