Fused deposition modelling (FDM) is one of the fastest-growing additive manufacturing methods used in printing fibre-reinforced composites (FRC). The performances of the resulting printed parts are limited compared to those by other manufacturing methods due to their inherent defects. Hence, the effort to develop treatment methods to overcome these drawbacks has accelerated during the past few years. The main focus of this study is to review the impact of those defects on the mechanical performance of FRC and therefore to discuss the available treatment methods to eliminate or minimize them in order to enhance the functional properties of the printed parts. As FRC is a combination of polymer matrix material and continuous or short reinforcing fibres, this review will thoroughly discuss both thermoplastic polymers and FRCs printed via FDM technology, including the effect of printing parameters such as layer thickness, infill pattern, raster angle and fibre orientation. The most common defects on printed parts, in particular, the void formation, surface roughness and poor bonding between fibre and matrix, are explored. An inclusive discussion on the effectiveness of chemical, laser, heat and ultrasound treatments to minimize these drawbacks is provided by this review.

FDM-Based 3D Printing of Polymer and Associated Composite: A Review on Mechanical Properties, Defects and Treatments.

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Recent progress in additive manufacturing of fiber reinforced polymer composite

Additive manufacturing of fiber reinforced composites is of great interest in various industrial applications. In this study, an innovative extruder is designed and manufactured for fused deposition modeling (FDM) 3D printers in order to produce continuous fiber reinforced thermoplastic (CFRT) composites. There are some challenges along this way such as making tension in fiber, fiber surface preparation, printing temperature and feed rate to produce a composite part with good quality. These challenges are discussed in detail. The main advantage of this extruder is that it can be mounted on the available FDM 3D printers and consequently there is no need to design a new chassis. In order to assess the quality of products, standard tensile and three-point bending specimens made of pure poly lactic acid (PLA) and carbon fiber reinforced PLA are printed and tested under quasi-static loading. Experimental results show significant improvements of tensile and bending properties of PLA. Morphological analysis is also conducted to study the bonding between the carbon fiber and PLA.

Mechanical characterization of FDM 3D printing of continuous carbon fiber reinforced PLA composites

A critical review on 3D printed continuous fiber-reinforced composites: History, mechanism, materials and properties

Fused deposition modelling (FDM) is a promising additive manufacturing technology and an alternative of conventional processes for the fabrication of fibre reinforced composites due to its ability to build functional parts having complex geometries. Continuous fibre reinforced thermoplastic composites (CFRTPCs) are becoming more significant in industrial applications due to their inherit advantages such as excellent mechanical performance, recycling and potential lightweight structures [1,2]. However, a major concern affecting the efficient use of 3D printed composites is the effect of impact damage on the structural integrity, compared to conventional pre-preg composites. The aim of this study is to evaluate the effect of build orientation, layer thickness and fibre volume content on the impact performance of 3D printed continuous carbon, glass, and Kevlar® fibre reinforced nylon composites, manufactured by FDM technique. Charpy impact tests are carried out to determine impact strength. SEM images of fractured surfaces are examined to assess failure mechanics of the different configurations. It is observed that the effect of layer thickness of nylon samples on the impact performance was different for flat and on-edge samples. Impact strength increases as layer thickness increases in flat samples but, conversely, it decreases in on-edge samples, depicting a more brittle fracture. In addition, the results show that impact strength increases as fibre volume content increases in most cases. Glass fibre reinforced samples exhibits the highest impact strength and carbon fibre reinforced samples the lowest one and similar to nylon performance. Furthermore, on-edge reinforced samples exhibit higher values of impact strength than flat reinforced samples. Finally, the results obtained demonstrate that impact strength exhibited by 3D printed composites are significantly higher than the usual 3D printed thermoplastics and, in some cases, even better than common pre-preg materials.

Impact damage resistance of 3D printed continuous fibre reinforced thermoplastic composites using fused deposition modelling

Characterization of 3D printed long fibre reinforced composites

Fracture resistance of 3D printed adhesively bonded DCB composite specimens using structured interfaces: Experimental and theoretical study

Experimental study of the size effect on transverse cracking in cross-ply laminates and comparison with the main theoretical models

Experimental failure investigation of pull-off tests of single T-stiffened composite specimens

Matrix/inter-fibre failure is characterized by the appearance at the fibre–matrix interfaces of small debonds that can progress along them until reaching a certain extension, then changing their orientation to kink towards the matrix and, finally, growing through it. The particular case of compressive loading is specially interesting, given the morphology of the interface cracks and the specific angle that the macro-cracks form in the matrix. To date, the analysis of this problem at micro-mechanical level has been carried out mainly by means of Finite Element or Boundary Element models. In this work, the problem is approached from the experimental point of view, observing under optical microscope those coupons previously tested at different loading levels. Several aspects such as the identification of the stages of the failure mechanism, the kinking angle, the extension of the interface cracks and the presence of damage as a function of the loading level are studied.

J. Justo

Papers

Characterization of 3D printed long fibre reinforced composites

Fracture resistance of 3D printed adhesively bonded DCB composite specimens using structured interfaces: Experimental and theoretical study

Experimental study of the size effect on transverse cracking in cross-ply laminates and comparison with the main theoretical models

Experimental failure investigation of pull-off tests of single T-stiffened composite specimens

Microscopical observations of interface cracks from inter-fibre failure under compression in composite laminates