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In industry, fused filament fabrication (FFF) offers flexibility and agility by promoting a reduction in costs and in the lead-time (i.e. time-to-market). Nevertheless, FFF parts exhibit some limitations such as lack of accuracy and/or lower mechanical performance. As a result, some alternatives have been developed to overcome some of these restrictions, namely, the formulation of high performance polymers, the creation of fibre-reinforced materials by FFF process and/or the design of new FFF-based technologies for printing composite materials. This work aims to analyze these technologies.

This work aims to study and understand the advances in the behaviour of 3D printed parts with enhanced performance by its reinforcement with several shapes and types of fibres from nanoparticles to continuous fibre roving. Thus, a comprehensive survey of significant research studies carried out regarding FFF of fibre-reinforced thermoplastics is provided, giving emphasis to the most relevant and innovative developments or adaptations undergone at hardware level and/or on the production process of the feedstock.

It is shown that the different types of reinforcement present different challenges for the printing process with different outcomes in the part performance.

This review is focused on joining the most important researches dedicated to the process of FFF-printed parts with different types reinforcing materials. By dividing the reinforcements in categories by shape/geometry and method of processing, it is possible to better quantify performance improvements.

The purpose of this paper is to present microstructural and fractographic analysis of damage in aluminum (2024T3)/carbon-fiber reinforced laminates (AlC) after static tensile test. The influence of fiber orientation on the failure was studied and discussed.

The subject of examination was AlC. The fiber–metal laminates (FMLs) were manufactured by stacking alternating layers of 2024-T3 aluminum alloy (0.3 mm per sheets) and carbon/epoxy composites made of unidirectional prepreg tape HexPly system (Hexcel, USA) in [0], [± 45] and [0/90]S configuration. The fractographic analysis was carried out after static tensile test on the damage area of the specimens. The mechanical tests have been performed in accordance to ASTM D3039. The microstructural and fractographic analysis of FMLs were studied using optical (Nikon SMZ1500, Japan) and scanning electron microscope (Zeiss Ultra Plus, Germany).

FMLs based on aluminum and carbon/epoxy composite are characterized by high tensile properties depending on their individual components and the orientation of the reinforcing fibers, failure of hybrid laminates indicates the complexity process of degradation of these materials. The nature of damage in FML layers is similar to that typical in polymer composites with interlaminar delaminations, transverse cracks of the composite layers, degradation of fiber/matrix interface, damage process in FMLs is also associated mainly with interface between metal and fiber reinforced composite. The mixed damage – cohesive and adhesive – was observed.

One of the most important aspect in the designing and manufacturing process in the service life of composite structures is damage mechanisms. The damage processes in composite materials, particularly in FMLs, are more complex in comparison to metal materials and fiber reinforced polymers.

This study aims to conduct an experimental study and finite element model (FEM) to investigate the flexural behavior of heat-damaged beams strengthened/repaired by hybrid fiber-reinforced polymers (HFRP).

Two groups of beams of (150 × 250 × 1,200) mm were cast, strengthened and repaired using different configurations of HFRP and tested under four-point loadings. The first group was kept at room temperature, while the second group was exposed to a temperature of 400°C.

It was found that using multiple layers of carbon fiber-reinforced polymer (CFRP) and glass fiber-reinforced polymer (GFRP) enhanced the strength more than a single layer. Also, the order of two layers of FRP showed no effect on flexural behavior of beams. Using a three-layer scheme (attaching the GFRP first and followed by two layers of CFRP) exhibited increase in ultimate load more than the scheme attached by CFRP first. Furthermore, the scheme HGC (heated beam repaired with glass and carbon, in sequence) allowed to achieve residual flexural capacity of specimen exposed to 400°C. Typical flexural failure was observed in control and heat-damaged beams, whereas the strengthened/repaired beams failed by cover separation and FRP debonding, however, specimen repaired with two layers of GFRP failed by FRP rupture. The FEM results showed good agreement with experimental results.

Few researchers have studied the effects of HFRP on strengthening and repair of heated, damaged reinforced concrete (RC) beams. This paper investigates, both experimentally and analytically, the performance of externally strengthened and repaired RC beams, in flexure, with different FRP configurations of CFRP and GFRP.

The purpose of this study is to understand the behavior of hybrid bio-composites under varied applications.

Fabrication methods and material characterization of various hybrid bio-composites are analyzed by studying the tensile, impact, flexural and hardness of the same. The natural fiber is a manufactured group of assembly of big or short bundles of fiber to produce one or more layers of flat sheets. The natural fiber-reinforced composite materials offer a wide range of properties that are suitable for many engineering-related fields like aerospace, automotive areas. The main characteristics of natural fiber composites are durability, low cost, low weight, high specific strength and equally good mechanical properties.

The tensile properties like tensile strength and tensile modulus of flax/hemp/sisal/Coir/Palmyra fiber-reinforced composites are majorly dependent on the chemical treatment and catalyst usage with fiber. The flexural properties of flax/hemp/sisal/coir/Palmyra are greatly dependent on fiber orientation and fiber length. Impact properties of flax/hemp/sisal/coir/Palmyra are depended on the fiber content, composition and orientation of various fibers.

This study is a review of various research work done on the natural fiber bio-composites exhibiting the factors to be considered for specific load conditions.

The aerospace, energy and automotive industries have seen wide use of composite materials because of their excellent mechanical properties, along with the benefit of weight reduction savings. As such, the purpose of this study is to provide an understanding of the mechanical performance of these materials under extreme operational conditions characteristic of in-service environments.

This study is novel in that it has evaluated the tensile performance and fracture response of additively manufactured continuous carbon fiber embedded in an onyx matrix (i.e. nylon with chopped carbon fiber) at cryogenic and room temperatures, for specimens manufactured with an angle between the specimen lying plane and the working build plane of 0°, 45° and 90°.

Research findings reveal enhanced tensile properties (i.e. ultimate tensile strength and modulus of elasticity) by the 0° (X) built specimens, as compared with the 45° (XZ45) and 90° (Z) built specimens at cryogenic temperature. A reduction in ductility is observed at cryogenic temperature for all build orientations. Fractographic analysis reveals the presence of fiber pullout/elongation, pores within the onyx matrix and chopped carbon fiber near fracture zone of the onyx matrix.

Research findings present tensile properties (i.e. ultimate tensile strength, modulus of elasticity and elongation%) for three-dimensional (3D)-printed onyx with and without reinforcing continuous carbon fiber composites at cryogenic and room temperatures. Reinforcement of continuous carbon fibers and reduction to cryogenic temperatures appears to result, in general, in an increase in the tensile strength and modulus of elasticity, with a reduction in elongation% as compared with the onyx matrix tensile performance reported at room temperature. Fracture analysis reveals continuous carbon fiber pull out for onyx–carbon fiber samples tested at room temperature and cryogenic temperatures, suggesting weak onyx matrix–continuous carbon fiber adhesion.

To the best of the authors’ knowledge, this study is the first study to report on the cryogenic tensile properties and fracture response exhibited by 3D-printed onyx–continuous carbon fiber composites. Evaluating the viability of common commercial 3D printing techniques in producing composite parts to withstand cryogenic temperatures is of critical import, for aerospace applications.

In this paper, continuous glass tow preg-reinforced acrylonitrile butadiene styrene (ABS) composites were fabricated by using a 3D printing method, and the purpose of this study is the investigation of the fiber preimpregnation effect on the mechanical behavior of these composites. In addition, a simple theoretical approach (mixture law), which considers the elastic behavior of reinforced composites and a numerical simulation method based on finite element method (FEM), was used to predict the tensile stress–strain behavior of ABS/glass tow preg composites in the elastic region.

Different groups of preimpregnated glass tows with various ABS amounts (named 2%, 10%, 20% and 30%) were prepared by the solution impregnation method. Then, preimpregnated glass tows (prepregs or tow-pregs) were fed into the printer head along with the polymeric ABS filament to print the composites. The tensile, flexural and short beam tests were conducted to evaluate the mechanical properties of the printed composites.

The first result of using tow-pregs instead of dry tows in continuous fiber 3D printing is much easier printing, printability improvement and the possibility of printing layers with low thickness, which can further increase the mechanical properties. The mechanical test results showed all of the glass prepregs improve strength and modulus in the tensile, three-point bending and short beam tests compared with neat ABS specimens, but statistical analysis showed that ABS weight percentage in the prepregs had no significant effect on the mechanical strength of composites except for the tensile modulus. Samples containing 2%-prepreg (minimum ABS amount in the tow-pregs) showed a significant improvement in tensile modulus. In the simulation section, good agreement is obtained between the model predictions and experimental tensile results. The results show that an acceptable deviation (14%) exists between the experimental and predicted value of elastic modulus by the numerical model.

To the best of the authors’ knowledge, this is the first study showing the effects of ABS weight percentage in prepregs on the mechanical properties of 3D printed continuous fiber-reinforced composites and predicting the mechanical behavior of 3D printed composites by numerical simulation method.

The mechanical and tribological properties of polymers and polymer composites vary with different environmental conditions. This paper aims to review the influence of humidity/water conditions on various polymers and polymer composites' mechanical properties and tribological behaviors.

The influence of humidity and water absorption on mechanical and tribological properties of various polymers, fillers and composites has been discussed in this paper. Tensile strength, modulus, yield strength, impact strength, COF and wear rates of polymer composites are compared for different environmental conditions. The interaction between the water molecules and hydrophobic polymers is also represented.

Pure polymer matrices show somewhat mixed behavior in humid environments. Absorbed moisture generally plasticizes the epoxies and polyamides and lowers the tensile strength, yield strength and modulus. Wear rates of PVC generally decrease in humid environments, while for polyamides, it increases. Fillers like graphite and boron-based compounds exhibit low COF, while MoS2 particulate fillers exhibit higher COF at high humidity and water conditions. The mechanical properties of fiber-reinforced polymer composites tend to decrease as the rate of humidity increases while the wear rates of fiber-reinforced polymer composites show somewhat mixed behavior. Particulate fillers like metals and advanced ceramics reinforced polymer composites exhibit low COF and wear rates as the rate of humidity increases.

The mechanical and tribological properties of polymers and polymer composites vary with the humidity value present in the environment. In dry conditions, wear loss is determined by the hardness of the contacting surfaces, which may not effectively work for high humid environments. The tribological performance of composite constituents, i.e. matrix and fillers in humid environments, defines the overall performance of polymer composite in said environments.

The purpose of this paper is to consider the static analysis of nanocomposite plates. Nanocomposites consist of a small amount of nanoscale reinforcements which can have an observable effect on the macroscale properties of the composites.

In the present study the reinforcements considered are non‐spherical, high aspect ratio fillers, in particular nanometer‐thin platelets (clays) and nanometer‐diameter cylinders (carbon nanotubes, CNTs). These plates are considered simply supported with a bi‐sinusoidal pressure applied at the top. These conditions allow the solving of the governing equations in a closed form. Four cases are investigated: a single layered plate with CNT reinforcements in elastomeric or thermoplastic polymers, a single layered plate with CNT reinforcements in a polymeric matrix embedding carbon fibers, a sandwich plate with external skins in aluminium alloy and an internal core in silicon foam filled with CNTs and a single layered plate with clay reinforcements in a polymeric matrix. A short review of the most important results in the literature is given to determine the elastic properties of the suggested nanocomposites which will be used in the proposed static analysis. The static response of the plates is obtained by using classical two‐dimensional models such as classical lamination theory (CLT) and first order shear deformation theory (FSDT), and an advanced mixed model based on the Carrera Unified Formulation (CUF) which makes use of a layer‐wise description for both displacement and transverse stress components.

The paper has two aims: to demonstrate that the use of classical theories, originally developed for traditional plates, is inappropriate to investigate the static response of nanocomposite plates and to quantify the beneficial effect of the nanoreinforcements in terms of static response (displacements and stresses).

In the literature these effects are usually given only in terms of elastic properties such as Young moduli, shear moduli and Poisson ratios, and not in terms of displacements and stresses.

The purpose of this study is for solving many issues in production that includes processing of complex-shaped profile, machining of high-strength materials, good surface finish with high-level precision and minimization of waste. Among the various advanced machining processes, abrasive jet machining (AJM) is one of the non-traditional machining techniques used for various applications such as polishing, deburring and hole making. Hence, an overview of the investigations done on carbon fiber-reinforced polymer (CFRP) and glass fiber-reinforced polymer (GRFP) composites becomes important.

Discussion on various approaches to AJM, the effect of process parameters on the glass fiber and carbon fiber polymeric composites are presented. Kerf characteristics, surface roughness and various nozzle design were also discussed.

It was observed that abrasive jet pressure, stand-off distance, traverse rate, abrasive size, nozzle diameter, angle of attack are the significant process parameters which affect the machining time, material removal rate, top kerf, bottom kerf and kerf angle. When the particle size is maximum, the increased kinetic energy of the particle improves the penetration depth on the CFRP surface. As the abrasive jet pressure is increased, the cutting process is enabled without severe jet deflection which in turn minimizes the waviness pattern, resulting in a decrease of the surface roughness.

The review is limited to glass fiber and carbon fiber polymeric composites.

In many applications, the use of composite has gained wide acceptance. Hence, machining of the composite need for the study also has gained wide acceptance.

The usage of composites reduces the usage of very costly materials of high density. The cost of the material also comes down.

This paper is a comprehensive review of machining composite with abrasive jet. The paper covers in detail about machining of only GFRP and CFRP composites with various nozzle designs, unlike many studies which has focused widely on general AJM of various materials.

Tribology of the carbon‐fibre‐reinforced plastics has been investigated. The wear‐resistance of carbon‐fibre‐reinforced plastics was found to be much better than those of other plastics reinforced with fibres of glass and stainless steel and was affected by the fibre‐orientation relative to sliding. Law of mixture in the frictional coefficient of composite materials was deduced; a comparison of calculated values with experimental data showed good agreements. Wear‐resistance of the carbon‐fibre‐reinforced plastics against fretting was also examined; good wear‐resistance was obtained when sliding within a region about 30° from the carbon‐fibre axis.