Experimental Determination of the Effective Filament Embedding Length for Composites Manufactured Using Additive Technologies

Abstract—The adhesive properties of the filament–matrix interface were studied in experiments on pulling filaments from a polymer matrix manufactured using additive technologies. The limiting shear stresses at the interface between the carbon filament and the polymer matrix are determined, as is the influence of the length of the filament “embedding” on the pulling force. For this purpose, specimens with different lengths of filament “embedding” were made. To estimate the displacement fields, the digital image correlation (DIC) method was used. Pictures of the fields of displacements and strains on the surface of the specimen were obtained, from which one can judge the processes occurring at the filament–matrix interface. The characteristic fields of strain when pulling a single filament from the matrix solid are shown. The length of the thread at which the load bearing capacity of the composite is realized more efficiently and the load is close to the limit for the filament itself was determined experimentally. Based on experimental data, the minimum effective length of filament “embedding” in the manufacturing of composite structural elements using additive methods was calculated.