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Additive manufacturing (AM) has enabled representative models and structures to be produce in a time-efficient manner relative to conventional subtractive manufacturing methods. In general, there has been wide-spread observation of fiber reinforced polymers improving the overall mechanical property of a part relative to the bulk resin or printed polymer. The strength and stiffness increases with fiber length; however, both stiffness and strength can be also greatly influenced by the type of AM process by which ultimately defines the microstructure of the material. While the stiffness and strength may be readily obtained by performing standardized mechanical tests, the influence of the microstructure given multiple-phases in an additively manufactured material is not generally well-understood or reported. A collection of microstructural information for a multi-phase composite consisting of discontinuous and matrix has been used for virtual characterization of the effective tensile properties by progressive failure analysis (PFA) in a representative volume element (RVE) in a stochastic fashion. Extended Finite Element Method (XFEM) combined with cohesive zone modeling was used to investigate the competing microscopic failure mechanism responsible for macroscopic mechanical properties of an AM composite. The development of comprehensive computational model will further inform the additive manufacturing process of AM materials to improve both the process and mechanical strength of the material. [ABSTRACT FROM AUTHOR]

The use of composite material is increasing because of its high strength to weight ratio. While composites have been around for decades, new applications where more complex shapes are needed are arising. The bladder assisted composite manufacturing (BACM) technique is a manufacturing process used for manufacturing complex hollow composite geometries. However, bladders can be expensive, complicated to repair, and frequently custom made. Hence, the use of 3D printed bladders is presented as an alternative solution for the BACM manufacturing method. The use of printed bladders is demonstrated by curing a composite part made out of IM7-8552. The bladders are additively manufactured with Thermoplastic Urethane (TPU). The thermoelastic behavior of the TPU used for printing the bladder is investigated through Dynamic Mechanical Analysis (DMA). Upon investigating the thermoelastic behavior of the TPU, a two-step cure cycle was designed for curing a composite part made with IM7-8552. In the first step, the composite part is partially cured and consolidated with the printed bladder, whereas in the second step, the part is fully cured at a more elevated temperature. The consolidation of the part made with this method is investigated and compared with traditional curing process, namely vacuum bag and autoclave. [ABSTRACT FROM AUTHOR]

To date, the Extrusion Deposition Additive Manufacturing (EDAM) process is largely an empirically calibrated system. Therefore, simulation tools are needed to predict residual stress and deformation states in printed parts. Tooling and molds are an initial application for fiber-reinforced polymer composite EDAM. In order to print high temperature tools for autoclave or even compression molding applications, high temperature thermoplastics are required for thermal stability. Carbon fiber-reinforced semi-crystalline polymers, such as polyphenylene sulfide (PPS) and polyether ether ketone (PEEK), are promising candidates. An additive manufacturing platform developed by Dassault Systemes was utilized in Abaqus 2017 to model the printing process of a 3D mold made from a semi-crystalline composite material. Here, custom user subroutines were used to model the transient thermal behavior and the crystallization phase transition of the material during the EDAM printing process. Furthermore, the resulting mold deformations and residual stresses were simulated based on both the thermomechanical and the crystallization shrinkage evolving during the transient process. The results shown in this paper demonstrate the capabilities of the developed simulation tools to predict mold performance and to aid part optimization. [ABSTRACT FROM AUTHOR]

The use of carbon fiber-reinforced polymer composites in extrusion deposition additive manufacturing (EDAM) has enabled upscaling this technology by reducing the deformation of the parts during printing. The presence of fibers reduces the coefficient of thermal expansion (CTE) and increases the elastic modulus of the printed material. Additive manufacturing molds is an application that benefits from both the ability to produce complex three-dimensional shapes with EDAM and the low CTE obtained with composites. In order to introduce the application of printed molds, this paper begins with describing the process to additive manufacture a composite mold. The example of a printed one-sided autoclave mold is utilized to describe the process and to introduce a simulation approach used for estimating the in-service deformation of a printed mold. Additionally, this paper demonstrates the use of a printed two-sided compression molding tool in a molding process. To the best of the authors' knowledge, this is the first ever printed compression mold that has been successfully tested. Finally, a deviation analysis of an autoclave printed mold was carried out to investigate the permanent deformation of the mold after undergoing an autoclave cure cycle at 180 °C. The results showed deviations from the original shape within around ±200 µm indicating that the tool can be utilized with confidence in a high-temperature autoclave cycle. [ABSTRACT FROM AUTHOR]

A growing and promising application of additive manufacturing (AM) is the production of tooling [1]. Since tooling is often produced in low volumes and custom geometries for specific products, AM is very attractive. Tooling used in the manufacturing of composite parts in particular stands to largely benefit from advances in AM technologies. The manufacturing of composite tooling usually involves wasteful subtractive processes and labor intensive steps, resulting in long lead times and high costs. Utilizing new AM technologies to manufacture composite tooling has the potential to produce significant savings in both time and cost. The past two years have seen rapid advancements in large scale AM, most notably the development of Big Area Additive Manufacturing (BAAM) by Oak Ridge National Lab (ORNL) and Cincinnati Incorporated (CI). The large build volumes and high throughput extrusion system now attainable with a commercial gantry system make AM an attractive new method for manufacturing composite tooling. The polymers utilized in the current generation of large scale AM machines possess lower glass transition temperatures and are likely most suitable for tooling masters or low temperature composite prototypes. Researchers at Purdue University have successfully printed with carbon fiber-reinforced Polyphenylene Sulfide (PPS), which is potentially suitable for production tooling with 350°F autoclave cure cycles. In the following, the process for manufacturing the composite tool shown in Figure 1 using AM will be discussed and the economics will be compared to a traditional tool manufacturing process. The cost savings achieved utilizing AM to manufacture this tool were approximately 50%. As tool size and complexity increase, cost savings are expected to become even greater. [ABSTRACT FROM AUTHOR]

Fused filament fabrication using fiber filled polymers produces parts with complex geometries, bead arrangement, and in-bead property variation. Understanding the microstructural impacts on bead and part level properties is critical for further process simulations and design improvements. This work presents a method using Digimat-FE [1] and SwiftComp [2] for determining final properties of a bead or part starting from knowledge of the microstructural geometry. [ABSTRACT FROM AUTHOR]

A numerical tool to model both the thermal history and the crystallization behavior of a 3D-printed part cross section made from a fiber reinforced semi-crystalline thermoplastic was developed with COMSOL, a multi-physics simulation code. The transient heat transfer analysis was coupled with a non-isothermal crystallization kinetics model in order to dynamically predict both the temperature- and crystallinity distribution during a printing process. Due the parametric nature of the model, arbitrary extrudate cross sections, material systems and printing speeds can be modeled. [ABSTRACT FROM AUTHOR]