This study investigates erosion behavior of oxide/oxide ceramic matrix composites (Ox/Ox CMCs) under varying thermomechanical conditions, including erosion-only, erosion-fatigue, and erosion-creep. Single and double-sided impacts were made at a temperature of 1200 degrees C, with particle velocity of 200 m/s. Optical microscopy with three-dimensional depth scanning was used to assess the extent of erosion damage, followed by room temperature tension tests to evaluate the remaining strength of eroded specimens. The objective was to assess the combined influence of stress, temperature, and velocity on erosion behavior and remaining strength of the Ox/Ox composites. The results showed linear increase in cumulative mass loss for all specimens. Specimens with erosion under stress exhibiting higher erosion rates compared to specimens with erosion only conditions. The combined influence of stress during erosion had a minimal effect on residual strength, as the erosion process itself was the primary driver of material degradation. On the other hand, double-sided impacts distributed damage more uniformly across the material, mitigating the effects of eccentricity and resulting in a slight increase in net-section stress. This suggests that erosion with stress has a limited direct impact on strength degradation and erosion by itself is the predominant factor influencing material degradation in high-temperature erosion conditions.

Large-Format Additive Manufacturing (LFAM) is emerging as a transformative technology with considerable potential across multiple sectors, provided that key implementation challenges are effectively addressed. Traditional trial-and-error methods are not practical due to their high costs and limited success in tackling the unique issues associated with LFAM, such as precise control of temperature, layer time, and problems related to layer adhesion, warping, and delamination. To overcome these challenges, the use of physics-based numerical simulations is essential for predicting and mitigating potential build defects, thereby improving build quality and reducing costs. This study presents a physics-based Integrated Computational Materials Engineering (ICME) approach for LFAM, demonstrated through a comprehensive case study of an LFAM-printed modular housing unit. The simulation framework incorporates micro-mechanics-based material modeling to characterize temperature-dependent mechanical properties, along with thermal analysis driven by machine GCode to accurately forecast temperature distribution during the printing process. This allows for the identification of optimal layer time parameters for recoating, enhancing layer adhesion, and minimizing defects. Additionally, mechanical analysis considers the raft and part clamping mechanisms during printing to identify issues such as warping, delamination, and Z-stress accumulation. The case study demonstrates the effectiveness of this simulation methodology through the fabrication of a 240” x 132” x 110” housing unit using recycled polyethylene terephthalate glycol with 30% glass fiber (PETG 30GF) material. This study not only highlights potential defects linked to the Gcode, but also identifies design features susceptible to high-stress concentrations and localized failures. Once the simulation methodology is validated, a compensated geometry is generated and printed to verify the quality improvement. Overall, this research underscores the critical role of physics-based simulations in addressing the inherent challenges of LFAM, facilitating informed decision-making, and accelerating technology adoption.

In recent years use of “virtual testing” has increased as an effort to evaluate new materials for structures earlier in the applications timeline. Virtual testing is made possible by conducting progressive failure analysis and combining it with available data to predict structure/component safety based on the physics of micro/macro mechanics of materials, manufacturing processes, and service environments. The US Airforce (AFRL) blind test lifing modeling challenges are described as virtual testing under In-service thermo-mechanical loading in two categories. The overall objective of these two efforts was to evaluate the best class invited computational models for accuracy and speed of simulations and to provide a theoretical prediction for damage and fracture evolution for a set of unnotched and notched laminated composites. Integrated Computational Material Engineering (ICME) and Computational Structural Mechanics (CSM) by Multiscale Progressive Failure Analysis (MS-PFA) were used to address the predictive evaluation of PMC and CMC materials using a building block validation strategy. ICME model considers nano-micro-mechanics coupled with Multi-scale progressive failure De-homogenized analysis to track damage/fracture evolution of laminated composites including: a) crack density formation in matrix, b) fiber damage and interphase/interface bridging, c) delamination, and d) crack initiation and propagation. Verification, Validation, and Accreditation (VVA) predictions for: 1) for the PMC IM7-977-3, static and fatigue simulation results were 12.8

In this study, anisotropic stiffness tensors were reconstructed based on fiber orientation distributions obtained from X-ray computer tomography (xCT). A preform was manufactured via a big area additive manufacturing (BAAM) system with carbon fiber (CF) filled acrylonitrile butadiene styrene (ABS). The tailored preform from additive manufacturing (AM) was used in the compression molding (CM) process to produce a low-void high-performance thermoplastic composite panel. An xCT technique was employed to detect the fiber orientations in CF/ABS composites manufactured via three different methods: AM from BAAM, extrusion compression molding (ECM), and AM-CM. The anisotropic stiffness tensor was obtained from the composite panel manufactured via the three manufacturing methods (AM, ECM, and AMCM). A micromechanics theory was used to obtain the orthotropic stiffness tensors of the composite panels and compared with the experimental values. The predicted stiffness tensors of AM and AM-CM composite panels were used to study the deformation characteristics of a steering wheel during airbag deployment by performing finite element analysis (FEA). The approach developed in this study can be utilized for evaluating high-performance composites.

Integrated Computational Material Engineering (ICME) framework for Air Plasma Spray (APS) process for ceramic coatings is developed for optimizing multifunctional coatings and APS process for Thermal Barrier Coating (TBC) system. ICME simulations of APS process for TBC, the burner rig test and furnace test of TBC have been performed along with the test validation of ICME predictions for Yttria-stabilized-zirconia (YSZ) TBC with APS 8YSZ top coating with / NiCoCrAlY bond over Waspaloy substrate. ICME predictions for residual deflection of TBC due to thermal loads after APS process, burner rig test and furnace test are in close agreement with the test results. Both test and ICME predictions show the as-manufactured TBC specimens exhibit bending after APS process and bending after Burner Rig and Furnace testing. Finite element model for TBC specimens shows bending induced by APS process, its thermal gradients and residual thermal stress. Microscale thermal models for APS process, burner rig test and furnace test have been used to predict thermal processes, porosity and stresses. Rumpling analysis of TBC predicts rumpling amplitude due to thermal stresses and thermal oxidation growth (TGO) in TBC, thickness of TGO, bond stress during rumpling and stresses in TGO layer. Predictions for the thickness of TGO compares well with experimental data. Progressive damage analysis revealed that failure is due to tension and out of plane shear, delamination growth due to oxidation penetrating YSZ TBC from the bond.

Composite Materials Qualification is intended for engineers, analysts, and end users with basic knowledge of composite materials and finite element analysis requesting more information on how to generate mechanical properties of composites and how to use it in structural analysis intended for part qualification and certification. The book consists of the following four chapters: In Chapter 1, a brief introduction to composite materials technology is presented along with its importance in both aerospace and automotive industries. Chapter 2 overviews the basic material properties, tests, and relevant procedures required to determine the engineering design values. Chapter 3 discusses the impact of variability on determining design values and methods of incorporating estimates of variability into design values. Chapter 4 provides a glimpse into the state-of-the-art computational methods and numerous references provided therein for analysis and design composite materials and structures, including constitutive modeling, homogenization methods, laminated plate theories, delamination, cohesive zone modeling, effect of defects, hygrothermomechanical modeling, residual stresses, and part distortion resulting from manufacturing and fatigue of composites. 83 pages, © 2021

The overall objective of this effort was to provide theoretical prediction for damage development for a set of laminated composites using AlphaSTAR Technology Solutions' (ATS's) commercial code GENOA (GENeral Optimization Analyzer) for the Air Force Research Laboratory (AFRL) program entitled "Assessment of Damage Progression Models for SiC/SiC Ceramic Matrix Composites (CMC Lifing Program)." Damage progression and prediction for advance ceramic matrix composite (CMC) benchmarks were done under static, fatigue, and creep service loading using test data from AFRL. Emerging and innovative multiscale (MS) modeling using computational structural mechanics (CSM) and progressive failure analysis (PFA) were proven to address the Air Force's vision to perform predictive evaluation of CMC materials using a building block validation strategy and certification process. Two different material systems and multiple layups were tested for both unnotched and notched configurations and at elevated temperatures. Calibration of the fiber and matrix properties was performed using in plane test data. The static, fatigue, and creep recalibration simulations of strength showed an average error of less than 10% between the simulation and test data. For stiffness the percent difference was found to be within 10% on average as well. All simulations used the same set of inputs (constituents, voids, fiber/matrix interphase, microcrack density, etc.) except for the noted analysis setting differences between blind and recalibration simulations. The method is consistent and follows a building block simulation approach that has an advanced yet simplistic theoretical multiscale progressive failure analysis (MS-PFA) approach.

During the 3D printing of graphene platelet inclusion in resin, residual stresses due to thermal loading can cause wrinkle/distortion of final part. This paper presents a multi-scale modeling approach to reduce the residual thermal stress at the interphase between inclusion and resin. Material characterization is performed utilizing an integrated multi-scale modeling approach: (a) nano modeling examines effect of defects such as void shape/size/distribution, platelet orientation, etc.); (b) micro-mechanics examines constituents (platelet/matrix/interphase, residual stress); (c) macro-mechanics examines the delamination and debonding. De-homogenized multi-scale modeling approach provides detailed stiffness/strength to Finite Element Model (FEM) for full structural/thermal progressive failure analysis to address wrinkling/distortion, damage and delamination evolution via cohesive traction separation.

This book is intended for engineer analyst end users with basic knowledge of composite material and finite element analysis requesting more information on how to design, build, and test a durable and damage-tolerant composite wind turbine blade. The wind blade industry utilizing composite materials is being periodically challenged with the manufacturing process, service load, nondestructive evaluation (NDE) and establishing material properties. In this chapter, discussions will be centered around: (1) composite material modeling and effect of defects using nanoassisted micromechanics algorithms; (2) structural design considerations of durability and reliability and scale-up; (3) blade manufacturing techniques; (4) virtual testing and building block validation strategy considering the effect of defects for in-service performance utilizing multiscale modeling; and (5) certification by analysis supported by minimum tests. There are multiple sections in this chapter and the highlights of these sections are the following: 1. Problems and challenges in the design of blade manufacturing, and material type, and structural concepts of as-built parts. Building block strategy to minimize tests, considering the effect of defects, scatter, uncertainty, and the environment in the material and the structure. 2. Detailed material property generation process of both unnotched and notched coupons of a typical toughened epoxy material system. In this section, the generated material properties are calibrated, validated, and predicted based on available test data. Further, the entire set of generated material properties is used as inputs to finite element analysis. 3. Detailed material allowable generation material scatter and uncertainty and CMH-17 authority definition and requirements, and available public data. 4. Discusses the in-service loading structural performance under static and fatigue cyclic loading. Emerging multiscale dehomogenized material models, and damage evolution process.

Part distortion and bottom surface warpage often occur in extrusion-based additive manufacturing. The undesirable deformations during the printing process are due to residual stresses caused by material shrinkage. Analysis on residual stress and deformation requires accurate thermo-mechanical material properties. Polymer composites reinforced with short fibers have intrinsic inhomogeneities with non-uniform fiber orientation. Therefore, homogenized macro properties may not accurately represent the progressive damage behavior or distortion. In this study, fiber orientations in Acrylonitrile Butadiene Styrene (ABS) reinforced with 20%wt carbon fiber are calculated using a de-homogenization technique. Thermal expansion coefficients in multiple directions are obtained from Thermo-Mechanical Analysis (TMA) tests. Temperature dependent stiffness is measured, and temperature dependent strength is estimated. Thermal conductivities in multiple directions and thermal capacity are measured. The calibrated thermo-mechanical properties of the composite with de-homogenized technique are used to analyze the residual stress and distortion of a 4 ft-wide wall printed in the Big Area Additive Manufacturing (BAAM) system. For experimental measurement on the wall printing, Infra-Red (IR) camera captures the temperature field, and Digital Image Correlation (DIC) camera captures the deformation field. Linear Variable Differential Transformer (LVDT) is installed to measure the warpage at the bottom surface. The experimental data are compared to the numerical analysis results. The temperature profile and the distortion profile from experiment are close to the simulation results. Damages due to residual stress and distortion are analyzed.

Familial chylomicronemia syndrome (FCS) is a rare genetic disorder affecting the body's ability to break down fats (lipids), characterized by severe hypertriglyceridemia and an increased risk of pancreatitis. In rare cases, pancreatitis can lead to acute complications which can lead to death. Pancreatitis can also have longer term complications including chronic pancreatitis or diabetes. Despite these potential serious complications, the mortality impact of pancreatitis is not well-understood. This study aimed to develop an analytical framework to extrapolate 2-year pivotal trial data to understand long-term risks of morbidity and mortality in patients treated with volanesorsen and standard-of-care (SoC) vs. SoC alone. Clinical trial data on patient outcomes for volanesorsen with SoC was assessed and compared to patients receiving only SoC treatment. Using evidence from literature, the key risks due to short-term outcomes were used to estimate long-term effects. Pre-determined criteria were used to filter the evidence based on quality, plausibility, and relevance. A patient flow analysis was constructed, and probabilistic modelling was applied to determine the likelihood of each complication/outcome to occur for each cohort. Model outcomes were then validated with clinicians/KOLs. The model provided a probabilistic comparison of different outcomes for patients with FCS. Results of the model showed that patients on SoC alone had a 76.8% increase in the risk of mortality by age 75 years compared to a 4.4% increase in the risk of mortality for patients receiving volanesorsen with SoC. This model provides a framework to assess the potential impact of a novel therapy in a rare disease but must not be taken out of context as a clinical claim. As a next step, monitoring will focus on how closely real-world outcomes compare with model outputs for further refinements.

A computational damage model, which is driven by material, mechanical behavior, and nondestructive evaluation (NDE) data, is presented in this study. To collect material and mechanical behavior damage data, an aerospace grade precipitate-hardened aluminum alloy was mechanically loaded under monotonic conditions inside a scanning electron microscope, while acoustic and optical methods were used to track the damage accumulation process. In addition, to obtain experimental information about damage accumulation at the laboratory scale, a set of cyclic loading experiments was completed using three-point bending specimens made out of the same aluminum alloy and by employing the same nondestructive methods. The ensemble of recorded data for both cases was then used in a postprocessing scheme based on outlier analysis to form damage progression curves, which were subsequently used as custom damage laws in finite element (FE) simulations. Specifically, a plasticity model coupled with stiffness degradation triggered by the experimentally defined damage curves was used in custom subroutines. The results highlight the effect of the data-driven damage model on the simulated mechanical response of the geometries considered and provide an information workflow that is capable of coupling experiments with simulations that can be used for remaining useful life (RUL) estimations.