Ceramic Matrix Composites: Session I
Sponsored by: ACerS Engineering Ceramics Division
Program Organizers: Narottam Bansal, NASA Glenn Research Center; Jacques Lamon, CNRS; Sung Choi, Naval Air Systems Command
Monday 8:00 AM
October 18, 2021
Room: B232
Location: Greater Columbus Convention Center
Session Chair: Marina Ruggles-Wrenn, Air Force Institute of Technology
8:00 AM
Synchrotron Tomography of SiC/SiC Minicomposites to Observe and Quantify Damage Evolution: Ashley Hilmas1; Andrew Sharits2; Craig Przybyla1; Robert Goldberg3; Amjad Almansour3; 1Air Force Research Laboratory; 2UES Inc; 3NASA Glenn Research Center
Composite performance is dictated by its microstructure – property relationships. For example, the characteristic response of ceramic matrix composites (CMCs) depends on the distribution of its constituents (i.e. fibers, matrix, fiber coatings, matrix cracks, and voids). Micro x-ray computed tomography (micro-CT) provides an opportunity to characterize the distribution of these constituents and to quantify the CMC microstructure in three-dimensions. To this end, In-situ micro-CT was performed at the Advanced Light Source (ALS) in combination with uniaxial tensile testing on SiC/SiC minicomposites. This work will describe the tensile load-dependent damage evolution within the microstructure of the SiC/SiC CMC specimens. The results from the micro-CT datasets can be used to develop micromechanical models that effectively capture damage initiation and progression in CMCs. In addition, details regarding the segmentation tools and techniques employed to understand and quantify these large tomography datasets will be presented.
8:20 AM
Interfacial Fracture Toughness on SiC/SiC CMCs: Oriol Gavalda-Diaz1; Luc Vandeperre1; Eduardo Saiz1; Finn Giuliani1; 1Imperial College London
Internal interphases in SiC/SiC are designed to achieve the graceful failure required in structural applications. Consequently, understanding interfacial crack propagation and measuring interfacial properties such as the fracture toughness, friction or residual stresses is crucial to understand, predict and model the failure of these materials and their degradation in different environments. In SiC/SiC materials the fibres are normally coated with graphite-like C or hexagonal BN interphases to achieve the desired interfacial properties. In this presentation we show different micromechanical tests that can be used to propagate a stable crack at the interfacial region and measure the interfacial fracture toughness. This includes micro Double Cantilever Beam (DCB) and push out tests using an SEM in-situ setup. With these tests we measure the Mode I and Mode II interfacial fracture toughness and we can distinguish the different debonding and fracture events as they occur.
8:40 AM
Developments in Laser-CVD to Produce SiC and Si3N4 Fibers for CMC Reinforcement: Ram Kiran Goduguchinta1; Joseph Pegna1; Mark Schaefer1; Jeff Vervlied1; 1Free Form Fibers
Free Form Fibers specializes in producing high-performance ceramic fibers for reinforcement materials in high-temperature, ultra-hard, Ceramic Matrix Composite (CMC) applications. A brief overview of our Laser-driven CVD (L-CVD) growth process, allowing the production of material from gaseous precursors, will be given. The advantages of utilizing this Additive Manufacturing-based approach to material fabrication is outlined, showing the main benefit of the L-CVD process as the ability to produce a fiber with no oxygen contamination. Enabling superior material properties, a breakdown on our recent developments regarding chemistry, characterization methods, and mechanical performance of silicon carbide and silicon nitride fibers will be presented. These materials are to be tested for tensile strength and creep resistance, and will be compared to other commercial fibers currently available on the market. Coupons with our fibers as reinforcement material will also be produced and discussed.
9:00 AM
Effectiveness of Mechanical Reinforcement of Carbon Nanotubes on Boron Carbide Through In-situ High Loading Indentation: Tyler Dolmetsch1; Benjamin Boesl1; Arvind Agarwal1; Cheng Zhang1; 1Florida International University
In this study, the effectiveness of the addition of carbon nanotubes (CNTs) on the mechanical reinforcement of boron carbide (B4C) composites synthesized by spark plasma sintering (SPS) was determined. CNTs of 2% and 4% weight fraction were homogenously dispersed into B4C powder and sintered via SPS. Samples were then subjected to high loading indentation using a Vickers indenter tip and load of 300 N. The energy dissipation and relative fracture toughness of the composites were calculated through load-displacement graphs. The total projected area of residual damage due to crack propagation was determined through scanning electron microscopy (SEM). In-situ high loading indentation inside the SEM was conducted and provided real time visualization of crack propagation and bridging, while also allowing for precise estimation of localized stresses required for nanotube pullout and failure mechanisms. Effectiveness of mechanical reinforcement was determined through comparison with a pure B4C sample.