Additive Manufacturing of Polymer Matrix Composites

Due to the developments and the interest of leading aerospace companies, additive manufacturing (AM) has become a highly discussed topic in the last decades. This is mainly due to its capability of producing parts with high geometrical complexity, short manufacturing lead times, and suitability for customization as well as for low-volume production. As is the case with aircraft fuselage body where weight reduction while keeping the demanding mechanical properties is of uttermost importance, modern technology applications sometimes need materials with unusual combinations of properties that cannot be solely provided by metals, polymers, or ceramics. In this case, composite materials combining two or more materials allow having the preferred properties in one material. Thus, AM of composites is becoming more and more important for critical applications. Fiber reinforcement can significantly enhance the properties of resins/polymeric matrix materials. Although continuous fiber composites even present higher mechanical performance, the manufacturing methods for chopped fibers are more commercially available. This chapter reviews the studies in the field involving many aspects spanning from design, process technology, and applications to available equipment

Numerical modeling of compression strengths of ti6al4v gyroid structures produced by laser powder bed fusion technology

Ortopedik metal implantlar fonksiyonun geri kazanılması amacıyla eklem ve kemik dokusunun onarımı sürecinde sağlamlığı korumak için yaygın kullanılır. İmplantların yük taşıma işlevi gören bölgeye uygun elastik modül değeri ve vücutta oluşacak olumsuz etkileri önleyici biyouyumluluk özelliklerinin olması, minimum gereksinimlerdir. İdeal implant malzemesi üzerine yaygınlaşmış çalışmalar, yüksek mekanik dayanıklılık ve osteointegrasyon özellikleri nedeniyle titanyum ve titanyum alaşımlı implantlar üzerinedir. Ancak implantasyon sonrası vücutta kalması istenen durumlarda biyoaktiviteyi daha da artırmak ve kemiğin mekanik özelliklerine yaklaşmak amacıyla üçlü periyodik minimal yüzey (ÜPMY) kafes yapısına sahip gözenekli implantlar kullanılır. Çalışma, istenen mekanik özellikleri ve gözenekler arası hücre hareketini sağlamak için kontrollü ÜPMY kafes yapılarından gyroid gözenek yapısına sahip lazer toz yatağında füzyon ile üretimi planlanan Ti6Al4V ilk olarak 40-80% arasında farklı gözeneklilik oranlarında tasarlanmıştır. Ardından her bir tasarım için basma altında mekanik dayanım ve deformasyon davranışlarını sonlu eleman analizi altında incelemeye odaklanılmıştır. Literatüre bakıldığında lazer toz yatağında füzyon ile üretilen gyroid Ti6Al4V yapıların basma testi sonuçları ile karşılaştırılmış ve uyumlu sonuçlar alınmıştır.Metal orthopedic implants are widely used to maintain stability during tissue repair in joint and bone injuries to restore function. Elastic modulus values suitable for the area where the implants carry the load-bearing part and have biocompatibility features that prevent harmful effects on the body are the minimum requirements. Widespread studies on the ideal implant material are on titanium and titanium alloy implants due to their high mechanical strength and osteointegration properties. However, in cases where it is desired to remain in the body after implantation, porous implants with triply periodic minimal surface (TPMS) lattice structures are used in order to increase the bioactivity further and reach the mechanical properties of the bone. In the study, Ti6Al4V with gyroid pore structure, one of the controlled TPMS lattice structures planned to be produced by laser powder bed fusion technology, was designed with different porosity rates between 40-80%. Then, the focus is on examining the mechanical strength and deformation behaviors under compression for each design with the finite element analysis. The results of the study were compared with the compression test of gyroid Ti6Al4V structures produced by laser powder bed fusion from the literature and consistent results were obtained

Investigation on Occurrence of Elevated Edges in Selective Laser Melting

Selective laser melting (SLM) is a layer-wise material additive process for the direct fabrication of functional metallic parts. During the process, successive layers of metal powder are fully molten and consolidated on top of each other by the energy of a high intensity laser beam. The process is capable of producing almost fully dense three-dimensional parts having mechanical properties comparable to those of bulk materials. However, one of the problems encountered in SLM process is the occurrence of elevated ridges of the solidified material at the edges of the successive layers. Those ridges reduce the dimensional accuracy and topology of the top surface. The edge-effect problem is encountered not only in SLM, but also in other production techniques applying melting processes such as LENS® (The Laser Engineered Net Shaping) and EBM (Electron Beam Melting). In this study, the reasons for elevated edges and solutions to this problem are investigated and reported. Different scan strategies as well as different hatching and contour parameters are tested to reduce the edge-effect problem. Besides, the influence of applying laser re-melting in combination to selective laser melting has been investigated. It turns out that re-melting layers deposited by SLM improves the part density and surface roughness, but creates on its own elevated edges.Mechanical Engineerin

Titanium based bone implants production using laser powder bed fusion technology

Additive manufacturing (AM) enables fully dense biomimetic implants in the designed geometries from preferred materials such as titanium and its alloys. Titanium aluminum vanadium (Ti6Al4V) is one of the pioneer metal alloys for bone implant applications, however, the reasons for eliminating the toxic effects of Ti6Al4V and maintaining adequate mechanical strength have increased the potential of commercially pure titanium (cp-Ti) to be used in bone implants. This literature review aims to evaluate the production of cp-Ti and Ti6Al4V biomedical implants with laser powder bed fusion (L-PBF) technology, which has a very high level of technological matureness and industrialization level. The optimization of L-PBF manufacturing parameters and post-processing techniques affect the obtained microstructure leading to various mechanical, corrosion and biological behaviors of the manufactured titanium. All of the features are considered in the light of specifications and needs of bone implant applications. The most critical disadvantages of the L-PBF technology, such as residual stresses and leading deformations are introduced and the potential solutions are discussed. Moreover, the manufacturability of porous bone implants that causes benefit and harm in L-PBF applications are assessed.Peer ReviewedObjectius de Desenvolupament Sostenible::3 - Salut i BenestarPostprint (published version

Understanding Adopting Selective Laser Melting of Metallic Materials

Additive manufacturing, considered as the future of manufacturing or the new industrial revolution, presents many advantages over conventional manufacturing. These include manufacturing integrated parts, eliminating joining processes, shortening lead times from design to testing, lightweight structures, being able to produce very complex geometries at almost no added cost, etc. Therefore, many industrial sectors such as aerospace, defense, biomedical and automotive, are getting more excited about adopting these technologies into their production lines. However, the shortage of experienced personnel in the field of Additive Manufacturing may make the transition period difficult and troublesome. Since AM technologies are rather new and immature compared to conventional manufacturing, many issues in terms of safety, environment, materials, process development, design guidelines as well as testing and validation arise. This paper will address and review lessons learned as a result of implementing selective laser melting for industrial applications as well as for research and development purposes so that this valuable outcome can be used as a guideline by beginners in this field.Mechanical Engineerin

A Review of the Additive Manufacturing of Fiber Reinforced Polymer Matrix Composites

Additive manufacturing (AM), also referred to as 3D printing, has gained popularity due to the recent developments and market trends especially in the last decades. The main advantages of AM are its capability of producing parts with high geometrical complexity at almost no added cost, short lead times, weight reduction, less efforts for assembly and suitability for customization as well as for low volume production or even single parts. Moreover, some applications may need materials with unusual combinations of properties, which cannot be provided only by metals, polymers or ceramics. For such applications, composite materials combining two or more materials allow having the preferred properties combined in a single material. Thus, AM, which can be defined as a process of adding materials to produce objects directly from its CAD model in successive layers in contrast to subtractive processes, is gaining significance for critical applications using composite materials. This paper thus presents a detailed review of AM of polymers reinforced with chopped / continuous fibers and the influence of this reinforcement on the mechanical performance of composite parts, mainly focusing on the Fused Deposition Modelling (FDM) process. On one hand, the reviewed studies on the FDM of composites mainly point out that that the mechanical performance is significantly enhanced in contrast to polymers with no reinforcement. Yet, it is also evident that the mechanical performance of FDM composites is highly dependent on the build direction and porosity. Thus, there is still a wide range of gaps to be studied for replacing metallic components by AM composites.Mechanical Engineerin

Dimensional Accuracy and Mechanical Properties of Chopped Carbon Reinforced Polymers Produced by Material Extrusion Additive Manufacturing

Fused Filament Fabrication (FFF), classified under material extrusion additive manufacturing technologies, is a widely used method for fabricating thermoplastic parts with high geometrical complexity. To improve the mechanical properties of pure thermoplastic materials, the polymeric matrix may be reinforced by different materials such as carbon fibers. FFF is an advantageous process for producing polymer matrix composites because of its low cost of investment, high speed and simplicity as well as the possibility to use multiple nozzles with different materials. In this study, the aim was to investigate the dimensional accuracy and mechanical properties of chopped carbon-fiber-reinforced tough nylon produced by the FFF process. The dimensional accuracy and manufacturability limits of the process are evaluated using benchmark geometries as well as process-inherent effects like stair-stepping effect. The hardness and tensile properties of produced specimens in comparison to tough nylon without any reinforcement, as well as continuous carbon-reinforced specimens, were presented by taking different build directions and various infill ratios. The fracture surfaces of tensile specimens were observed using a Scanning Electron Microscope (SEM). The test results showed that there was a severe level of anisotropy in the mechanical properties, especially the modulus of elasticity, due to the insufficient fusion between deposited layers in the build direction. Moreover, continuous carbon-reinforced specimens exhibited very high levels of tensile strength and modulus of elasticity whereas the highest elongation was achieved by tough nylon without reinforcement. The failure mechanisms were found to be inter-layer porosity between successive tracks, as well as fiber pull out

An Experimental study of Process Parameters in Laser Marking

Laser marking produces an indelible mark on a workpiece by the energy of a laser beam, mostly for the purposes of product identification and traceability. Being a fast, flexible and clean method, it is superior to other techniques such as ink-marking, mechanical engraving and electro-chemical methods. Workpieces made from metal, plastics and ceramics as well as coated materials and even the smallest electronic components can be marked quickly, efficiently and consistently. In the current study, laser marking is applied with the laser source of a standard RP/RM machine, i.e. a selective laser melting machine. This makes laser marking especially suited for marking parts produced by laser RP/RM techniques. However, there are various process parameters influencing the mark readability, mark contrast and profile. This research enlightens the influences of three main parameters, namely scan speed, laser power and pulse frequency of a Q-switched Nd:YAG laser. Single-factor experimental strategy is applied for marks on grinded AISI 1085 steel workpieces. The physical phenomena causing different profiles at various parameter combinations are discussed including recoil pressure, oxidation and thermal gradients which are present in the melt pool.status: publishe

Application of Laser Re-melting on selective laser melting parts

status: publishe