Session: 12-02-02: Modeling of the Fracture, Failure, and Fatigue in Solids

Paper Number: 113081

113081 - Discrete, Meso-Scale Modeling of Fiber-Reinforced Composites (Dm4c): Application to the Additive Manufacturing of Continuous Fibers 

Thanks to the outstanding mechanical properties in terms of specific stiffness and strength, fiber-reinforced composites have been used in various engineering applications such as aviation, civil infrastructures, and automobile industry. Conventional manufacturing methods of composite structures often require an extensive involvement of manual labor, resulting in high manufacturing costs and inconsistent part quality. To address these problems, automated technologies such as automated fiber placement (AFP) and 3D printing of continuous fibers aim at reducing manufacturing costs, paving new avenues for attritable aircrafts. However, composite structures manufactured with these methods contain inherent defects such as gaps and overlaps, porosity, tow misalignments and tow waviness produced during production process, introducing another complexity to the structural analysis. This makes the design and certification of composites made via AFP or Additive Manufacturing (AM) inherently more challenging than for traditional composites.
In this study, we provide a novel discrete approach (DM4C) in constitutive modeling of the mechanical behavior of fiber-reinforced composite materials towards the application of AM. Common and widespread methods of modeling composite is to
treat lamina/laminate as a homogeneous medium, which is quite opposite to the true meso-structure of fiber reinforced composites. By averaging out the material response, this approach reduces the resolution and the accuracy in capturing damage initiation to progression. This includes phenomena such as micro-buckling of fibers under compression, and matrix micro-cracking, which are inherently induced by the characteristics of the micro- or meso-structure of composite materials.
Furthermore, it is difficult to include the effect from defects induced from manufacturing process.

We propose to explicitly model fiber tows and matrix, resembling closely to the meso-scale structure of fiber-reinforced composites in DM4C. A tetrahedral mesh where fiber tows are embedded as Timoshenko beam elements produces facets that surround beams by triangulation. We provide the state-of-the-art and highly parallelized fiber generation algorithm suited for designing 3-D printed composites with continuous and/or discontinuous fiber reinforcement. Explicit representation of fibers as beams allows to use input from a manufacturing process. This helps to naturally capture processing defects such as gaps and overlaps by modeling fiber beams following the exact paths and directly modeling gaps in tetrahedral mesh; consequently, improving the accuracy of the structural analysis. The constitutive law for matrix is formulated in each facet resembling the lattice discrete particle model. The vectorial form of constitutive relation similar to microplane formulation presents simple and physics-based description of the material, avoiding unnecessary curve-fitting parameters. Furthermore, the discrete description of damage morphology prevents the element erosion under large deformation. After the sections describing the theoretical aspects of the model, we investigate the capability of material characterization via calibration with 3-D printed unidirectional composites. We conclude our studies with some preliminary studies on the composite parts using AM technology.

Presenting Author: Marco Salviato Department of Aeronautics and Astronautics

Presenting Author Biography: Dr. Salviato is an associate professor in the William E. Boeing Department of Aeronautics and Astronautics of University of Washington where he serves as the PI of the laboratory for Multiscale Analysis of Materials and Structures (MAMS). Before joining the University of Washington in 2015, Dr. Salviato obtained a Ph.D. in Theoretical and Applied Mechanics in 2013 from the University of Padova (Padova, Italy) with a doctoral dissertation focusing on the experimental characterization and computational modeling of polymer nanocomposites. He later joined the Department of Civil and Environmental Engineering at Northwestern University as postdoctoral scholar (2013-14) and research assistant professor (2014-15).
Dr. Salviato’s research and teaching interests lie in the area of Computational Mechanics and Fracture Mechanics of Quasibrittle Solids. His goal is understanding the mechanical behavior of materials and structures at multiple length-scales through the formulation of advanced computational and analytical approaches, and new experimental techniques. He believes that the next-generation, damage-tolerant infrastructure will be enabled by the elimination of the old dichotomy between the concepts of “structure” and “material”. His work has been funded by several agencies and industrial sponsors including the Federal Aviation Administration, the National Science Foundation, the Air Force Research Laboratory, DoE, and Boeing.
In 2017, Dr. Salviato received the prestigious ASME Haythornthwaite Young Investigator Award for “excellence in theoretical and applied mechanics”. In 2020, he was the recipient of the DSTech Young Composites Researcher Award, an honor bestowed by the American Society for Composites on the most promising young researchers in the field of composites. In 2021, Dr. Salviato was selected by the National Academy of Engineering (NAE) among the most promising young engineers to participate in the prestigious 2021 NAE US Frontiers of Engineering Symposium. He was later selected as an NAE Grainger Foundation Frontiers of Engineering Grant awardee. In 2021, Dr Salviato published the book “Quasibrittle Fracture Mechanics and Size Effect: A First Course” (Oxford University Press) with co-authors Dr. Le (University of Minnesota) and Dr. Bažant (Northwestern University).

Authors:

Marco Salviato Department of Aeronautics and Astronautics
Antonio Deleo University of Washington
Sean Phenisee University of Washington
Daniele Pelessone ES3 inc
Mark Flores Air Force Research Laboratory (AFRL)