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Until recently, glass fiber composites (GFRP) were the preferred choice to prepare wind turbine blades due to their low cost compared to their counterpart carbon fiber composites (CFRP). However, to harvest the maximum wind energy, ever larger wind turbine blades are being manufactured. To support such a large structure carbon fiber composites CFRP have become the integral part of load bearing structures in the blade. In this work, we are proposing to utilize the low cost carbon fiber (LCCF), manufactured at Carbon Fiber Technology Facility (CFTF) of Oak Ridge National Laboratory (ORNL) as not only the cost effective alternative to the currently used carbon fiber (CF) but also as the lightning strike protection of the wind turbine blades. A textile-grade precursor was used to prepare LCCF. Wind turbines often get hit by lightning strikes due to their operating locations. LCCF can provide structural integrity to these gigantic structures and mitigate the effect of lightning strike on them by effectively dissipating the current. Two composite panels made of LCCF were tested against artificial lightning strikes of 100 kA and 200 kA (component A of lightning

The large scale extrusion deposition process has recently been commercialized in the form of additive manufacturing machines such as the BAAM from Cincinnati Inc., which enables layered production of chopped fiber reinforced thermoplastic polymer systems. The application of this process to the automotive market is being pursued by Local Motors to enable rapid design to market cycles and build on-demand capability for a wide range of vehicle styles from a distributed network of micro-factories. This endeavor will require an understanding of the structural performance of components with complex geometries, where the properties are known to vary as a function of printing conditions, as well as orientation and shape. In order to rapidly build a database of structural performance, a beam specimen with outer dimensions of 914 x 305 x 64 mm3 was selected to be subjected to bending, torsion, and shear loading with full field displacement measurement by digital image correlation (DIC). A total of 25 different specimen configurations were designed including variation of print geometry, reinforcement by foam filling, and overwrapping with advanced composites. This work documents the results of the study and presents the relative performance of the structures in addition to the approach to simulation that is being initiated to serve as a framework for efficient design of structures manufactured in this way. The results are presented as a table of structural efficiency including stiffness and strength as functions of mass for each design. Additional results will also be provided in the form of surface displacements from DIC; future work will utilize this data to better optimize simulations for predicting structural performance of articles manufactured by this process.

Extrusion Deposition Additive Manufacturing (EDAM) is a technology where 3-D digital objects are manufactured extruding beads of molten material in a layer-by-layer basis. This technology offers the flexibility for processing pelletized material, and thus a semi-crystalline polymer highly-filled with carbon fiber has been used for printing. Significant technology improvements in the EDAM technology have been made recently, however, the design of the printing strategy is still mostly driven by empirical development. Hence, there is a need for simulation tools that capture the phenomena involved in the EDAM process to drive the development and optimization of this technology. Currently, one limitation of printed parts in terms of mechanical properties is the strength of the interface developed between printed layers. Therefore, the focus of this work is to couple the phenomena involved in the bonding process of adjacent layers to predict the degree of bonding, such as the temperature history, the melting and crystallization of the semi-crystalline polymer and the diffusion of polymer chains. The models utilized to describe these phenomena and their couplings were implemented in a UMATHT user subroutine in Abaqus to predict the evolution of the degree of bonding during the EDAM process. The effects of the couplings implemented in this approach are demonstrated by predicting the evolution of the degree of bonding throughout the simulation of the printing process of a geometry with sections that undergo different cooling and crystallization rates.

The Extrusion Deposition Additive Manufacturing (EDAM) process, more commonly known as Fused Deposition Modeling (FDM) or Fused Filament Fabrication (FFF), is a promising new manufacturing method for high temperature tooling and molds. However, nowadays this process is still largely empirically calibrated. Based on the required capabilities for determining residual stresses and the final deformation state of printed parts and their effects on the part performance, there is a large interest in the development of process simulations. To this end, a set of simulation tools has been implemented in Abaqus/Standard through a user subroutine suite at Purdue University to model the EDAM process. This work extends these simulation capabilities to include thermoviscoelastic material properties. An incremental linear thermoviscoelastic model is presented for an anisotropic material and implemented in Abaqus with a UMAT user subroutine. The thermoviscoelastic properties of a 50wt.% carbon fiber reinforced Polyphenylene Sulfide (PPS) were characterized in relaxation experiments and the implemented model was verified using the experimental data. To assess the significance of crystallization informed thermoviscoelastic material properties, process simulation results were compared for an autoclave tool. Here, the outcomes of the thermoviscoelastic analysis were compared with a simulation considering temperature dependent elastic properties. The results of this comparison indicate that it is essential to capture viscoelasticity that is informed by crystallization in order to predict realistic stress levels for subsequent performance analyses. In addition to the stresses, the resulting final deformations differ significantly for both analyses as well. The different internal stress levels after deposition and the crystallization informed material stiffness in the thermoviscoelastic analysis are the main causes for this deviation.