Graphene oxide does not seem to improve the fracture properties of injection molded

ABSTRACT: Scientific literature presents a number of examples in which the mechanical properties of materials are significantly improved by adding small amounts of nano-particles. In many cases, the addition of such nano-particles is performed on polymer-matrix composites, with reported improvements in mechanical, optical, thermal or electrical properties. Therefore, the potential of this technology is huge and a great deal of research work is being performed with the aim of generating new advanced engineering materials. However, this paper presents the other side of the coin. The authors have introduced small amounts of Graphene Oxide (up to 1%) in PA6 with the aim of studying their effect on the fracture properties of the resulting composites. For the particular conditions analyzed here, no improvements in the fracture behavior (in both cracked and notched conditions) have been observed (a similar conclusion may be obtained for the tensile behavior). Other types of material properties were not covered in the analysis. Sharing this kind of (negative) results may save other researchers time and budget, and it is a much more common practice in other fields of science.The authors of this work would like to express their gratitude to the Spanish Ministry of Science and Innovation for the financial support of the project PGC2018-095400-B-I00 “Comportamiento en fractura de materiales compuestos nano-reforzados con defectos tipo entalla”, on the results of which this paper is based

Characterization of Stiffness Degradation Caused By Fatigue Damage of Additive Manufactured Parts

A study of the cyclical fatigue behavior of additive manufactured components, fabricated by the fused deposition modeling (FDM) process, is presented. Experimentation was designed to focus on the effect of deposition strategy or specimen mesostructure on tensile fatigue life and effective stiffness. Testing included consideration of unidirectional laminates with parallel plies having fiber orientations ranging from q = 0° to q = 90°, and bidirectional laminates with alternating orthogonal plies that form a layering pattern of q°/(q - 90°) fiber orientations. Results highlight the orthotropic behavior of FDM components and suggest that tensile performance is improved by aligning fibers of unidirectional laminae more closely with the axis of applied stress. The bidirectional laminae display incrementally improved tensile fatigue performance from what appears to be an offsetting effect associated with alternating orthogonal layers. An empirical model of effective elastic modulus and an analytical model of the accumulated damage state, as defined on the basis of stiffness degradation during cyclical loading, are presented as functions of specimen mesostructure. The actual damage accumulation due to cyclical loading is compared with the model predictions, and the coefficient of determination R2 indicates reasonable agreement for each factor combination