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Digital Composite Materials

Title: Design and Fabrication of Aerospace-Grade Digital Composite Materials
Researchers: Xiao Liu, Ronen Yudzinsky, Christopher Hansen
Sponsors: Early Career Faculty grant (No. NNX14AO50G) from NASA’s Space Technology Research Grants Program Foundation
The Overall Goal of this project:
The aim of this project is to advance fundamental knowledge-based design tools and manufacturing approaches for 1-D and 2-D fiber-reinforced composite “digital material” (i.e., discrete) elements with simple, yet strong internal joining to enable increased structural design flexibility and decreased structural mass in aerospace applications. 

The project will pursue these objectives by the design, fabrication, and characterization of a library of 1-D and 2-D discrete composite elements. The primarily axial loading of slender 1-D struts optimizes fibers to axial orientations; research emphasis will instead be placed on (1) increased buckling loads for compressive members, (2) decreased mass for all members, (3) rapid manufacturing throughput, and (4) improved joining techniques. 1-D struts will be computationally designed (FEA) to improve specific (i.e., per mass) buckling performance via core material removal. These internally structured designs will be fabricated via high-throughput composite pultrusion with embedded sacrificial filaments, so that the fugitive material removal provides core insert locations. Inserts into these internal cavities will reversibly join neighboring struts to efficiently transfer load transfer; snap-fit joints proven in civil engineering systems will likewise be explored. 1-D tensegrity structures will further reduce mass via distinct compression and tensile strut populations; these elements will be computed via the reduced coordinates method, which is best suited to control element lengths necessary for discrete components, and then experimentally characterized. Discretized 2-D plate elements remove the 1-D strut fiber orientation constraint and open a vastly expanded parameter space for anisotropic fiber-reinforced materials. Regular polygons will be investigated to obtain maximum fiber orientations per plate population; these elements will be superimposed onto topologies obtained from SIMP and BESO numerical techniques, and from multiphysical models. The 2-D parts library will be fabricated via automated composite deposition to produce micro-structured plates that are representative of composite shell structures and which similarly exploit sacrificial internal cavities for simple assembly of strong joints. 

My Current Research:
Experimental and theoretical study of lightweight fiber-reinforced composite structures particularly using anisotropy in structures subject to buckling. Most structures for which buckling is an issue are designed to resist buckling. Another portion the research is focused on developing and prototyping an innovative automation solution for fabricating the lightweight fiber-reinforced composite structures with 1,2 and 3 dimensional shapes. This automation solution is designed to avoid in-process defects (e.g. voids and resin reach area) within the final parts and decrease the capital cost for the fabrication.