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The purpose of this study is to increase the thermal and mechanical properties of the photopolymer by filling with the copper powder for the application of rapid tooling.

In this study, the photopolymer is filled with the different loading of copper powder for investigating the thermal and mechanical properties of the copper/photopolymer composite. The thermal properties of the copper/photopolymer composite are characterized with the degradation temperature and with the thermal conductivity. The mechanical properties of copper/photopolymer composite are performed with the tensile strength and hardness testing. Moreover, the copper/photopolymer composite is imaged by using a scanning electron microscopic with energy dispersive spectroscopy.

The tensile strength of the copper/photopolymer composite is increased over 45 per cent at 20 phr copper loading. The hardness of the photopolymer has a negative correlation with the increasing copper loading and is decreased about 28.5 per cent at 100 phr copper loading. The degradation temperature of the copper/photopolymer composite is increased about 7.2 per cent at 70 phr copper loading. The thermal conductivity of the copper/photopolymer composite is increased over 65 per cent at 100 phr copper loading.

The photopolymer used in rapid prototyping system is generally fragile and has poor thermal properties. This study improves the thermal and mechanical properties of the photopolymer with the copper filling which has been never investigated in the field of rapid prototyping applications.

The purpose of this paper is to evaluate the mechanical properties of photopolymer/CB (carbon black) nanocomposite when applied in a visible-light rapid prototyping (RP) machine.

The mechanical properties of the samples such as hardness and tensile strength along with thermal stability were analyzed. The curing time behavior of the photopolymer/CB nanocomposites was tested by using a rigid-body pendulum rheometer. The shrinkage property and dimensional stability were also analyzed using the technique according to ASTM D2566 and ASTM D1204, respectively.

The results showed that the prototype fabricated from pristine photopolymer tended to exhibit poor mechanical properties and low thermal stability. However, after adding the photopolymer with various concentrations of nano-CB and dispersant in appropriate composition, the photopolymer/CB nanocomposite prototype not only reduced its curing time but also enhanced its mechanical properties, thermal stability and dimensional stability.

The presented results can be used in a visible-light RP machine.

The mechanical and thermal properties of photopolymer are improved with nano-CB additives for a RP system.

Polymeric parts produced by 3D stereolithography (SL) process have poorer mechanical properties as compared to their counterparts fabricated via conventional methods, such as injection or compression molding. Adding nanofillers in the photopolymer resin for SL could help improve mechanical properties. This study aims to achieve enhancement in mechanical properties of parts fabricated by SL, for functional applications, by using well-dispersed nanofillers in the photopolymers, together with suitable post-processing.

Carbon nanotubes (CNTs) have high strength and Young’s modulus, making them attractive nanofillers. However, dispersion of CNTs in photopolymer is a critical challenge, as they tend to agglomerate easily. Achieving good dispersion is crucial to improve the mechanical properties; thus, suitable dispersion mechanisms and processes are examined. Solvent exchange process was found to improve the dispersion of multiwalled carbon nanotubes in the photopolymer. The UV-absorbing nature of CNTs was also discovered to affect the curing properties. With suitable post processing, coupled with thermal curing, the mechanical properties of SL parts made from CNTs-filled resin improved significantly.

With the addition of 0.25 wt.% CNTs into the photopolymer, tensile stress and elongation of the 3D printed parts increased by 70 and 46 per cent, respectively. With the significant improvement, the achieved tensile strength is comparable to parts manufactured by conventional methods.

This allows functional parts to be manufactured using SL.

In this paper, an improved procedure to incorporate CNTs into the photopolymer was developed. Furthermore, because of strong UV-absorption nature of CNTs, curing properties of photopolymer and SL parts with and without CNT fillers were studied. Optimized curing parameters were determined and additional post-processing step for thermal curing was discovered as an essential step in order to further enhance the mechanical properties of SL composite parts.

The purpose of this paper is to present a novel method to design and manufacture rapid prototyping (RP) lightweight photopolymer‐resin models for wind‐tunnel tests. This method can ensure the structural configuration similarity considering model deformation under aerodynamic loads.

Photopolymer‐resin based on RP technique was used to fabricate DLR‐F4 models. Testing in a subsonic and transonic wind tunnel was carried out and the test results were compared to analyze performance predictions.

RP photopolymer‐resin wind‐tunnel models fabricated by the design methods yielded satisfactory aerodynamic performance. The methods can decrease the model's weight and prevent resonance occurrence among the models, wind‐tunnel, and support system, shorten the processing period, and lead to decrease in manufacturing period and cost.

Stiffness shortage of the thin components, such as wing tip, often leads to deformation occurrence under aerodynamic loads in transonic wind‐tunnel tests, which has significant influence on aerodynamic characteristics of the test models. Therefore, model deformation should be taken into account in the design process.

This design and manufacture method, aerodynamic and structural combination design and structural optimization, can obtain RP lightweight photopolymer‐resin wind‐tunnel models for satisfactory aerodynamic performance, which makes RP techniques more practical for manufacturing transonic wind‐tunnel test models, considering deformation induced by aerodynamic forces such as lift force. The methods also present an inexpensive way to test and evaluate preliminary aircraft designs, in both academia and industry.

Refers to how the mechanical properties of polymer‐based composite objects produced via rapid layered fabrication methods can be improved significantly using short discontinuous fibres as reinforcements. Notes in this context, that the viscosity of the uncured fibre‐photopolymer composite liquids affects the raw‐material handling, the layer formation and the draining operations. Assesses the effects of aspect ratio, surface coating and volume fraction of short glass fibres on the viscosity of the fibre‐photopolymer composite liquids. Based on extensive experimentation and analysis, concludes that the shear viscosity of the composite liquids increases with increasing fibre‐volume fraction, showing that this effect is more pronounced at low shear rates than at high shear rates. Reveals, similarly, that the aspect ratio of the dispersed fibres has a stronger effect on the increase of viscosity at low shear rates and that the surface coating of the dispersed fibres also affects the viscosity of the composite liquids.

The purpose of this paper is to study the mechanical property of three-dimensional (3D) Printed photopolymer (Vero Yellow and Tango Black) with different constant strain rate. According to the experimental results, three constitutive models are used to describe the stress-strain and stress-time relation in the tension and stress relaxation process.

The Stratasys Objet 260 was used to prepare the four groups of samples with different photopolymers (Vero Yellow and Tango Black). The stress-strain and stress-time relations are obtained by the uniaxial tensile tests and relaxation tests performed at room temperature with different constant strain rates. The generalized Kelvin model (GKM), standard linearized model (SLM) and fractional order model (FOM) are used to describe experimental data by means of the curve-fitting approach.

Experimental results show that the tension stress increases faster at a higher strain-rate for tensile tests. Relaxation stress is influenced by the preload strain-rate for relaxation tests. For the theoretical fitting, the error comparison between three constitutive models and experimental data are calculated to demonstrate the high accuracy in describing the stress-strain relationship for tension. For stress relaxation, the error comparison confirms higher accuracy of FOM with the largest error within 3%, while the error of GKM and SLM up to 10%.

The paper confirms the viscous-elastic mechanical property of 3D printed photopolymer composites (Vero Yellow and Tango Black) for Stratasys PolyJet. As FOM shows high accuracy both in describing stress-strain and stress-time relation for tension and stress relaxation process, it can be directly used as a constitutive model to predict mechanical properties for engineering application.

The democratization of invention is a long lasting desire for the advancement of society. Having access to education and the means of production appears as the major factors for the implementation of this goal. 3D printing is a revolutionary technology that has the potential to bring digital manufacturing to everyone. However, the rise of personal fabrication requires an increase in printing quality, a reduction on machine cost and an increase in knowledge shared by the open hardware community. The purpose of this paper is to explore the development of a new Open Hardware printer project to address these points.

The authors have designed and constructed a low-cost photopolymer-based 3D printer called BeamMaker. The printer is connected to a host computer and a digital-light-processing projector. This work details the design process and how improvements were implemented to reach good printing quality. The authors provide public access to the instructions, software, source code, parts list, user manual and STL and CAD files.

The BeamMaker printer can build objects with a high surface quality that is comparable to the quality obtained by industrial photopolymer-based 3D printers. When testing the ability to print a sample cylinder, the printer shows higher accuracy when compared to other personal 3D printers. These findings are encouraging considering the low cost of the system.

The printing failure rate of the system has not been measured to date. The system requires some improvements to produce large objects.

The printer cost is just USD380. This is five to eight times less expensive than popular personal 3D printers available today. The cost is 30 times less expensive than a personal photopolymer 3D printer produced by a main commercial company and yet producing results of similar quality. The authors expect good avenues for collaboration from the open-source community to continue improving these systems.

The high cost of current personal 3D printers prevents users from developing countries from entering into the open hardware trend. A dramatic reduction in printer cost such as that explored in this work might contribute to the real democratization of personal fabrication.

The authors report on the status of three other photopolymer-based personal 3D printer projects. To the best of the authors' knowledge, BeamMaker is the first fully open hardware 3D printer project which uses this technology.

During post-processing of stereolithography photopolymers, the limited penetration depth of ultraviolet (UV) light can lead to inhomogeneous cross-linking. This is a major problem in part design for industrial applications as this creates uncertainty regarding the mechanical load capacity. Therefore, this paper aims to present an experimental method to measure the post-curing depth in stereolithography photopolymers.

Printed specimens made from urethane acrylate photopolymers are placed in a protective housing and are exposed on one side to UV light during post-processing. A depth profile of the hardness according to ASTM D2240 Shore D is determined alongside the specimens. UVA,-B and -C spectra are investigated and the dependence on exposure dose and pigmentation is studied. The results are directly linked to the mechanical properties via tensile tests and validated on an automotive trim part.

Exposure with a 405 nm light-emitting diode provides the deepest homogenous post-curing depth of 10.5 mm, which depends on the overall exposure dose and pigmentation. If the initially transparent photopolymer is colored with black pigments, post-curing depth is significantly reduced and no homogenous post-curing can be achieved. To obtain comparable mechanical properties by tensile tests, complete cross-linking of the specimen cross-section has to be ensured.

The spatial resolution of the presented measurement method depends on the indenter size and sample hardness. As a result, the resolution of the used setup is limited in the area close to the edges of the specimen.

This paper shows that the spatially resolved hardness measurement provides more information on the post-curing influence than the evaluation of global mechanical properties. The presented method can be used to ensure homogenous cross-linking of stereolithography parts.

Direct ink writing (DIW) is a robust additive manufacturing technology for the fabrication of fiber-reinforced thermoset composites. However, this technique is currently limited to low design complexity and minimal heights. This study aims to investigate the feasibility of UV-assisted DIW of composites to enhance the green-part strength of the printed inks and resolve the complexity and the height limitations of DIW technology.

The experimental approach involved the preparation of the thermoset inks that are composed of nanoclay, epoxy, photopolymer and glass fiber reinforcement. Composite specimens were fabricated in complex geometries from these ink feedstocks using UV-assisted, hybrid 3D-printing technology. Fabricated specimens were characterized using optical microscopy, three-point bending mechanical tests and numerical simulations.

The introduced hybrid, UV-assisted 3D-printing technology allowed the fabrication of tall and overhanging thermoset composite structures up to 30% glass fiber reinforcement without sagging during or after printing. Glass fiber reinforcement tremendously enhanced the mechanical performance of the composites. UV-curable resin addition led to a reduction in strength (approximately 15%) compared to composites fabricated without UV resin. However, this reduction can be eliminated by increasing the glass fiber content within the hybrid thermoset composite. Numerical simulations indicate that the fiber orientation significantly affects the mechanical performance of the printed composites.

This study showed that the fabrication of high-performing thermoset composites in complex geometries was possible via hybrid DIW technology. This new technology will tremendously expand the application envelope of the additively manufactured thermoset composites and the fabrication of large composite structures with high mechanical performance and dimensional freedom will benefit various engineering fields including the fields of aerospace, automotive and marine engineering.

The advantages of incorporating permanent photopolymer (dry film solder mask) coatings into high density printed wiring designs to obtain maximum component density and high reliability are discussed. Although originally developed for use as solder masks, these materials offer significant advantages to the PCB designer. Specific items to be discussed include high density conductor routing, in accordance with the proposed MIL STD 275D, on the solder side and under closely spaced components, component and heat sink mounting, the use of permanent polymer coatings to avoid metallic growth problems, new industry and military specifications and standards that relate to the incorporation of photopolymer masks into PCB designs and effects of coatings on high density, controlled impedance transmission lines.