Mechanical properties for long fibre reinforced fused deposition manufactured composites

In this work, we analyse the results of the reported mechanical properties for a particular kind of continuous fibre-reinforced thermoplastic composites (CFRTPC) manufactured by fused deposition modelling (FDM). A summary of reported mechanical properties available in Scopus and Web of Science databases as well as cross-references was gathered. Listed materials include a Nylon matrix reinforced with continuous fibres of carbon (CRTP), Kevlar (KvRTP), and fibreglass (FGRTP) used for the Markforged printer. The reported experiments are tension, bending, and shear, where fibres were oriented at 45° from the load axis. The reported properties include elasticity modulus, Poisson ratio, ultimate stress in a parallel-to-load direction, and, in some cases, the same properties in the perpendicular-to-load direction. For impact, there was found a comprehensive study reporting Izod testing. Moreover, fatigue is reported for FGRTP composites under uniaxial alternative testing, with one of them testing CRTP, and KvRTP as well as providing Wohler curves. Fractography is also discussed. There is also one study reporting creep testing. From the summary of reported properties, it was found a wide variation of mechanical properties, lack of reporting of an appropriate fibre volume fraction and how such content was estimated. The paper discusses reported mechanical properties under different types of loading for three types of CFRTPC composites, CRTP, FGRTP, and KvRTP. Finally, there are recommendations to perform missing studies reporting relevant aspects of damage mechanisms in composites such as wear, water absorption, UV effect on mechanical properties, toughness, and fatigue crack growth threshold.