Effect of the fiber orientation on the tensile and flexural behavior of continuous carbon fiber composites made via fused filament fabrication

Abstract

Recent years have seen the wide diffusion of composite materials in many manufacturing fields and the rapid evolution of additive manufacturing. Lately, these technologies have been combined practically allowing the fabrication of continuous-fiber reinforced polymer parts via 3D-printing. This topic is gaining attention both in the research community and among industrial users. Because of their novelty, such manufacturing methods are, however, still not thoroughly understood, and their performance limits have not yet been fully characterized. This study aims at analyzing the mechanical resistance of components made with continuous carbon fiber (CCF) thermoplastic materials by means of fused filament fabrication (FFF), focusing on the influence of the fiber orientation on such properties. In particular, both the tensile and the bending characteristics are evaluated according to the relative test standards, in specimens with both unidirectional and mixed-isotropic configurations. The experimental findings are compared with a set of reference specimens made with a base polymer filled with chopped “short” carbon fibers, allowing one to appreciate the advantages or limitations of the different fiber arrangements.

Pin-bearing mechanical behaviour of continuous reinforced Kevlar fibre composite fabricated via fused filament fabrication

“…7). The results were in contrast to those obtained in [11]. The specimen with fibres oriented at 0° exhibited optimal performances during the tensile test.…”

“…In particular, it was observed that samples with fiber along 0 and 90° has higher stiffness and resistance to bearing strength, this phenomenon is coherent with the results obtained by [11] in case of tensile test. However, respect to [11] better results have been achieved with Test 0-90 mixed or simple comparing with results of Test 0°; the reason is caused by the stress distribution that in pin bearing is not constant but varies from zero at the sides of the hole to a maximum behind the pin. In accordance with [11] no significative results have been observed for mixed or single configuration.…”

“…This can occur not only in the load direction. Hence, this is contrary to [11], which states that 90° fibres cannot improve mechanical properties during the tensile test. Furthermore, high stiffness was observed for fibres oriented parallel to the load direction.…”

“…Furthermore, high stiffness was observed for fibres oriented parallel to the load direction. However, the stiff-ness decreased for the fibre orientation of 45° during the tensile test [11]. Specifically, it was only 8.3% higher than that of the unreinforced configuration.…”

“…In literature, several characterizations have been performed on CRFC reinforced with carbon, glass and Kevlar fibres printed with FFF additive technology. The main mechanical behaviour evaluated is the response to the tensile test and the results founded could be resumed as follow: higher performances with carbon reinforcement respect to glass and Kevlar [9,10]; fiber layer position distribution does not affect the tensile strength [11] and elastic modulus [12]; presence of voids occurs with the increase of consecutive fibres layer [13]; best reinforcements achievable when fibres are oriented parallel to the loading direction [14]; CRFC parts produced with additive manufacturing technology has lower properties respect to traditional methods because of layering production process [15,16]; it exists a trade off in terms of quality comparing long and short fibre [17]; highest rigidity achievable with layers of matrix and fibres alternated of ± 45° respect to the load direction [18].…”