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Carlsbad, CA, United States

Gowayed Y.,Auburn University | Ojard G.,Aerojet Rocketdyne | Ojard G.,UTRC - United Technologies Research Center | Santhosh U.,Structural Analytics, Inc. | Jefferso G.,Air Force Research Lab
Journal of Composite Materials | Year: 2015

The feasibility of utilizing the shear lag theory to estimate crack density in fabric reinforced composites was investigated. A geometric model was constructed for the fabric and meshed using a hybrid finite element approach. The small segment of the yarn and the surrounding matrix enclosed within each element were treated as a unidirectional composite and the shear lag theory was used to estimate the crack density. Model results were compared to experimental data for a 5- harness satin melt-infiltrated SiC/SiC composite under tension and showed a pattern similar to experimental data with the model starting to accumulate cracks at a stress corresponding to the point of departure from linearity in the stress- strain curve while cracks were experimentally observed around 60 MPa higher. The model and experimental data had a similar value for the crack density at the saturation level. Sensitivity analysis showed that the crack density was highly sensitive to the fiber volume fraction in the load direction followed by the weave angle of the crimped segments of the yarns and the interfacial shear strength between the fibers and the matrix. © 2014 The Author(s). Source


Gowayed Y.,Auburn University | Ojard G.,Aerojet Rocketdyne | Prevost E.,Aerojet Rocketdyne | Santhosh U.,Structural Analytics, Inc. | Jefferson G.,Air Force Research Lab
Composites Part B: Engineering | Year: 2013

Defects created during the manufacture of an oxide/oxide and two non-oxide (SiC/SiNC and MI SiC/SiC) ceramic matrix composites (CMCs) were categorized as follows: (1) Intra-yarn defects such as dry fibers, (2) Inter-yarn defects such as those at crossover points, matrix voids, shrinkage cracks and interlaminar separation, and (3) Architectural defects such as layer misalignment. Their impact on elastic properties was analytically investigated using a stiffness averaging approach considering the defects to have volumetric and directional influences. In-plane tensile and shear moduli as well as the through-thickness compressive modulus were experimentally evaluated. Results of analytical model were around 7% on average from the mean value of the experimental data. It was observed that interlaminar separation drastically reduced the through-thickness modulus by about 63% for the SiC/SiNC, 40% for the MI SiC/SiC and around 32% for the oxide/oxide composites. Shrinkage cracks in oxide/oxide composite reduced the in-plane tensile and shear moduli by 14% and 8.8%, respectively. © 2013 Elsevier Ltd. All rights reserved. Source


Grant
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 149.95K | Year: 2015

ABSTRACT: Innovative research and development leading to a dual-use advanced technology product is proposed. The product is a methodology and associated software for modeling nonlinear response of carbon-fiber reinforced composite materials such as carbon/carbon (C/C) and carbon/silicon-carbide (C/SiC), and design of their components. Once developed and validated, the methodology would be used in cost effective development of C/C and C/SiC components, such as Thermal Protection Systems (TPS) and missile cones by the Air-Force and its major hypersonic weapons suppliers. The proposed methodology would be applicable to a broad class of C/C and C/SiC components for military and commercial applications. An innovative Physics-Based mechanistic modeling approach is proposed. The approach, based on an existing validated modeling approach for SiC/SiC Ceramic-Matrix Composites, includes direct consideration of relevant defect and damage mechanisms and environmental degradation. Utilization of existing models developed for similar materials and building on them will result in shorter model development times and more efficient use of Air-Force resources. Phase I will include characterization of deformation and damage in mechanistic model for C/C and C/SiC materials mostly from literature in order to understand any deformation mechanisms unique to these material systems. The models will be validated against benchmark and sub-element test data. Predictions will be compared with experimental measurements to assess the modeling approach and feasibility for a comprehensive methodology development in Phase II. BENEFIT: Due to the proliferation in potential applications of C/C and C/SiC composites in military applications such as TPS and shields for hypersonic bodies, and in commercial applications, such as aircraft brakes, the proposed dual-use high technology product has an immediate and expanding market. The biggest benefit of the proposed product is in its ability to improve the design of carbon-reinforced composite components taking advantage of its inherent nonlinear behavior. SAI will market the methodology, the software and technical expertise (services) to these and other industries.


Grant
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase II | Award Amount: 749.80K | Year: 2012

ABSTRACT: Innovative research and development leading to a dual-use advanced technology product is proposed. The product is a methodology and associated software for a damage-based non-linear deformation model to study the effect of manufacturing defects and service-induced damage in Ceramic Matrix Composites (CMCs). Once developed, the model would be used in conjunction with non-destructive evaluation (NDE) methods to predict the effect of defects and damage on structural properties, component life and residual strength. The primary focus is on 2D SiC/SiC and S200 CMCs for the gas turbine components. However the methodology would be applicable to a much broader class of CMCs and components for military and commercial applications. An innovative mechanistic (physics-based) modeling approach is proposed. The approach includes direct consideration of relevant defect and damage mechanisms. During Phase I models to describe the effect of defects such as matrix porosity and fiber fracture were developed and it was also demonstrated how the quantitative model inputs can be obtained using NDE techniques such as X-ray CT-scan. In Phase II we propose to continue the development and validation of the methodology in order to extend the applicability of the model to a variety of conditions relevant to aircraft operating conditions. NDE and laboratory test data needed to validate the model will be obtained under subcontract with Triton Systems, Inc. Pratt & Whitney. BENEFIT: Due to the proliferation in potential applications of ceramic matrix composites in military and commercial aerospace engines and in industrial gas turbine industries, the proposed dual-use high technology product has an immediate and expanding market. In conjunction with NDE techniques the proposed product will benefit these programs by improving the process of evaluation of as-manufactured CMC parts to sufficiently meet desired structural properties and design goals. The proposed product will also be useful in in-service component inspection and evaluation to estimate residual properties. SAI will market the methodology, the software and technical expertise (services) to these and other industries.


Grant
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase II | Award Amount: 749.88K | Year: 2012

ABSTRACT: The goal of the proposal is to develop life-prediction methodology and associated software for a damage-based non-linear deformation model to study the effect of manufacturing defects and service-induced damage in Ceramic Matrix Composites (CMCs). Once developed and thoroughly validated, the methodology would be used in cost effective development of CMC components by the Air Force and its major aerospace engine suppliers. The proposed methodology is based on a mechanistic (physics-based) model that includes direct consideration of defect and damage mechanisms, and environmental degradation relevant to CMCs. In Phase I the feasibility of using methodology to model effect of defects and to do life prediction of CMC materials has been demonstrated by comparison with limited amount of experimental data. The proposed Phase II effort aims to extend the applicability of the model to a variety of conditions relevant to aircraft operating conditions. The resulting enhancements will be experimentally validated and demonstrated. BENEFIT: Due to the proliferation in potential applications of ceramic matrix composites in military and commercial aerospace engines and in industrial gas turbine industries, the proposed dual-use high technology product has an immediate and expanding market. One benefit of the proposed product is in improving the process of evaluation of as-manufactured CMC parts to sufficiently meet desired structural life. The proposed product will also be useful in in-service component inspection and evaluation to estimate residual life. SAI will market the methodology, the software and technical expertise (services) to these and other industries.

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