scholarly journals The Structural Integrity of Composite Materials and Long-Life Implementation of Composite Structures

2020 ◽  
Vol 27 (5) ◽  
pp. 449-478
Author(s):  
Peter W. R. Beaumont
Keyword(s):  
Composite Structures ◽  
Large Scale ◽  
Structural Integrity ◽  
Mechanical Performance ◽  
Crack Nucleation ◽  
Intelligent Manufacturing ◽  
Structural Level ◽  
Fundamental Understanding ◽  
Semi Empirical ◽  
Crack Nucleation And Growth

Abstract Empirical or semi-empirical design methodologies at the macroscopic scale (structural level) can be supported and justified only by a fundamental understanding at the lower (microscopic) size scale through the physical model. Today structural integrity (SI) is thought as the optimisation of microstructure by controlling processing coupled with intelligent manufacturing of the material: to maximise mechanical performance and ensure reliability of the large scale structure; and to avoid calamity and misfortune. SI analysis provides quantitative input to the formulation of an appropriately balanced response to the problem. This article demonstrates that at the heart of the matter are those mechanisms of crack nucleation and growth that affect the structural integrity of the material: microscopic cracking events that are usually too small to observe and viewed only by microscopy.

scholarly journals Mechanisms Controlling the Performance and Durability of Thermal Barrier Coatings

2000 ◽  
Author(s):  
Daniel R. Mumm ◽  
Anthony G. Evans
Keyword(s):  
Thermal Cycling ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Large Scale ◽  
Mechanical Performance ◽  
Thermal Protection ◽  
Crack Nucleation ◽  
Ceramic Coatings ◽  
Thermal Barrier ◽  
Barrier Coatings

Abstract Thermal protection systems based on ceramic thermal barrier coatings (TBCs) are used extensively to protect hot-section components in gas turbine engines. They comprise thermally insulating ceramic coatings, deposited on an aluminum-containing intermetallic bond coat (BC) that provides oxidation protection. A thin thermally-grown oxide (TGO layer forms between the TBC and BC during cyclic thermal exposure. Each of the system constituents evolves in service and all interact during thermal cycling to control the thermo-mechanical performance of the system. Exposed to thermal cycling conditions, TBC systems are susceptible to loss of adhesion and spalling failures. Multiple failure mechanisms exist, dependent upon differing thermal histoiy and processing approach for various coating systems. Coating failure is ultimately controlled by the large residual compression in the TGO and its role in amplifying the effects of imperfections in the vicinity of the TGO. The failure occurs through a process involving crack nucleation, propagation and coalescence events. For a particular commercial system, it is found that the TGO ‘ratchets’ into the bond coat with each thermal cycle, at an array of interfacial sites. The displacements induce strains in the superposed TBC that cause it to crack. The cracks extend laterally as the TGO ratcheting process proceeds, until the cracks from neighboring sites coalesce. Once this happens, the system fails by large scale buckling. It is shown that the displacements are ‘vectored’ by a lateral component of the growth strain in the TGO. The relative roles of bond coat visco-plasticity, initial interface morphology, and phase evolution are discuss. The behavior observed for this system is compared with predictions of a ratcheting model, as well as with the behavior observed for other commercial coating systems.

scholarly journals Use of microfasteners to produce damage tolerant composite structures

2016 ◽  
Vol 374 (2071) ◽  
pp. 20150277 ◽  
Author(s):  
Ivana K. Partridge ◽  
Stephen R. Hallett
Keyword(s):  
Composite Structures ◽  
Structural Integrity ◽  
Mechanical Response ◽  
Mechanical Performance ◽  
Crack Opening ◽  
Complex Loading ◽  
Mechanical Tests ◽  
Crack Bridging ◽  
Delamination Crack ◽  
Out Of Plane

The paper concerns the mechanical performance of continuous fibre/thermosetting polymer matrix composites reinforced in the through-thickness direction with fibrous or metallic rods or threads in order to mitigate against low delamination resistance. Specific illustrations of the effects of microfasteners in reducing delamination crack growth are made for Z-pinned and tufted composites. Response to loading in such ‘structured materials’ is subject to multiple parameters defining their in-plane and out-of-plane properties. Single microfastener mechanical tests are well suited to establish the crack bridging laws under a range of loading modes, from simple delamination crack opening to shear, and provide the basis for predicting the corresponding response of microfastener arrays, within a given material environment. The fundamental experiments on microfasteners can be used to derive analytical expressions to describe the crack bridging behaviour in a general sense, to cover all possible loadings. These expressions can be built into cohesive element constitutive laws in a finite-element framework for modelling the effects of microfastener arrays on the out-of-plane mechanical response of reinforced structural elements, including the effects of known manufacturing imperfections. Such predictive behaviour can then be used to assess structural integrity under complex loading, as part of the component design process. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

scholarly journals Structural integrity of engineering composite materials: a cracking good yarn

2016 ◽  
Vol 374 (2071) ◽  
pp. 20160057 ◽  
Author(s):  
Peter W. R. Beaumont ◽  
Costas Soutis
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Large Scale ◽  
Structural Integrity ◽  
High Efficiency ◽  
Human Life ◽  
Engineering Structures ◽  
Catastrophic Fracture ◽  
Materials Used ◽  
Integrity Analysis

Predicting precisely where a crack will develop in a material under stress and exactly when in time catastrophic fracture of the component will occur is one the oldest unsolved mysteries in the design and building of large-scale engineering structures. Where human life depends upon engineering ingenuity, the burden of testing to prove a ‘fracture safe design’ is immense. Fitness considerations for long-life implementation of large composite structures include understanding phenomena such as impact, fatigue, creep and stress corrosion cracking that affect reliability, life expectancy and durability of structure. Structural integrity analysis treats the design, the materials used, and figures out how best components and parts can be joined, and takes service duty into account. However, there are conflicting aims in the complete design process of designing simultaneously for high efficiency and safety assurance throughout an economically viable lifetime with an acceptable level of risk. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

Life-cycle health monitoring of composite structures using piezoelectric sensor network

2021 ◽  
Author(s):  
yinghong yu ◽  
Xiao Liu ◽  
jun li ◽  
Yishou Wang ◽  
xinlin qing
Keyword(s):  
Life Cycle ◽  
Sensor Network ◽  
Lead Zirconate Titanate ◽  
Health Monitoring ◽  
Composite Structures ◽  
Large Scale ◽  
Structural Integrity ◽  
Piezoelectric Sensor ◽  
Curing Process ◽  
Whole Life Cycle

Abstract The vacuum-assisted resin infusion (VARI) technique provides considerable advantages in manufacturing large-scale composite structures. An accurate and consecutive structural health monitoring system is urgently required to determine the initial quality and assess the structural integrity of a composite structure. In this paper, a real-time active smart diagnostic system (SDS) based on piezoelectric sensor network is proposed to monitor the whole life-cycle of composite structures. Experiments were conducted on carbon fiber reinforced plastic (CFRP) specimens with different thicknesses to investigate the monitoring capability of piezoelectric lead-zirconate-titanate (PZT) sensors used in the SDS approach. The PZT sensor networks inserted inside the composite structures during the VARI process are used to monitor not only the curing parameters, but also the health status of composite structures when they are in service after curing. To monitor the curing process only, the sensor network can also be installed on the bottom of the mould. Experimental results demonstrate that both three-dimensional resin flow and degree of cure (DOC) in the VARI process can be effectively monitored by the PZT sensor network. Meanwhile, the embedded PZT sensor network has the potential to identify the different stages in the curing process. It is obvious that the piezoelectric sensor network will provide important technical support for composite materials with the structure and function integrated.

scholarly journals Computational and experimental mechanical performance of a new everolimus-eluting stent purpose-built for left main interventions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Saurabhi Samant ◽  
Wei Wu ◽  
Shijia Zhao ◽  
Behram Khan ◽  
Mohammadali Sharzehee ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Mechanical Performance ◽  
Experimental Studies ◽  
Patient Specific ◽  
Wall Structure ◽  
Left Main ◽  
Element Analysis ◽  
Stent Expansion ◽  
Radial Strength ◽  
Different Diameters

AbstractLeft main (LM) coronary artery bifurcation stenting is a challenging topic due to the distinct anatomy and wall structure of LM. In this work, we investigated computationally and experimentally the mechanical performance of a novel everolimus-eluting stent (SYNERGY MEGATRON) purpose-built for interventions to large proximal coronary segments, including LM. MEGATRON stent has been purposefully designed to sustain its structural integrity at higher expansion diameters and to provide optimal lumen coverage. Four patient-specific LM geometries were 3D reconstructed and stented computationally with finite element analysis in a well-validated computational stent simulation platform under different homogeneous and heterogeneous plaque conditions. Four different everolimus-eluting stent designs (9-peak prototype MEGATRON, 10-peak prototype MEGATRON, 12-peak MEGATRON, and SYNERGY) were deployed computationally in all bifurcation geometries at three different diameters (i.e., 3.5, 4.5, and 5.0 mm). The stent designs were also expanded experimentally from 3.5 to 5.0 mm (blind analysis). Stent morphometric and biomechanical indices were calculated in the computational and experimental studies. In the computational studies the 12-peak MEGATRON exhibited significantly greater expansion, better scaffolding, smaller vessel prolapse, and greater radial strength (expressed as normalized hoop force) than the 9-peak MEGATRON, 10-peak MEGATRON, or SYNERGY (p < 0.05). Larger stent expansion diameters had significantly better radial strength and worse scaffolding than smaller stent diameters (p < 0.001). Computational stenting showed comparable scaffolding and radial strength with experimental stenting. 12-peak MEGATRON exhibited better mechanical performance than the 9-peak MEGATRON, 10-peak MEGATRON, or SYNERGY. Patient-specific computational LM stenting simulations can accurately reproduce experimental stent testing, providing an attractive framework for cost- and time-effective stent research and development.

The assessment of density functionals for DNA–protein stacked and T-shaped complexes

2010 ◽  
Vol 88 (8) ◽  
pp. 815-830 ◽  
Author(s):  
Lesley R. Rutledge ◽  
Stacey D. Wetmore
Keyword(s):  
Amino Acid ◽  
Potential Energy ◽  
Large Scale ◽  
Enzymatic Reaction ◽  
Basis Sets ◽  
Density Functionals ◽  
Interaction Energies ◽  
Π Interactions ◽  
Hybrid Techniques ◽  
Semi Empirical

The present work uses 129 nucleobase – amino acid CCSD(T)/CBS stacking and T-shaped interaction energies as reference data to test the ability of various density functionals with double-zeta quality basis sets, as well as some semi-empirical and molecular mechanics methods, to accurately describe noncovalent DNA–protein π–π and π+–π interactions. The goal of this work is to identify methods that can be used in hybrid approaches (QM/MM, ONIOM) for large-scale modeling of enzymatic systems involving active-site (substrate) π–π contacts. Our results indicate that AMBER is a more appropriate choice for the lower-level method in hybrid techniques than popular semi-empirical methods (AM1, PM3), and suggest that AMBER accurately describes the π–π interactions found throughout DNA–protein complexes. The M06–2X and PBE-D density functionals were found to provide very promising descriptions of the 129 nucleobase – amino acid interaction energies, which suggests that these may be the most suitable methods for describing high-level regions. Therefore, M06–2X and PBE-D with both the 6–31G(d) and 6–31+G(d,p) basis sets were further examined through potential-energy surface scans to better understand how these techniques describe DNA–protein π–π interactions in both minimum and nonminimum regions of the potential-energy surfaces, which is critical information when modeling enzymatic reaction pathways. Our results suggest that studies of stacked nucleobase – amino acid systems should implement the PBE-D/6–31+G(d,p) method. However, if T-shaped contacts are involved and (or) smaller basis sets must be considered due to limitations in computational resources, then M06–2X/6–31G(d) provides an overall excellent description of both nucleobase – amino acid stacking and T-shaped interactions for a range of DNA–protein π–π and π+–π interactions.

scholarly journals Investigating the Effect of Interface Morphology in Adhesively Bonded Composite Wavy-Lap Joints

2021 ◽  
Vol 5 (1) ◽  
pp. 32
Author(s):  
Roya Akrami ◽  
Shahwaiz Anjum ◽  
Sakineh Fotouhi ◽  
Joel Boaretto ◽  
Felipe Vannucchi de Camargo ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Composite Structures ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Tensile Load ◽  
Lap Joints ◽  
Load Level ◽  
Displacement Curve ◽  
Interface Morphology ◽  
Angle Variation

Joints and interfaces are one of the key aspects of the design and production of composite structures. This paper investigates the effect of adhesive–adherend interface morphology on the mechanical behavior of wavy-lap joints with the aim to improve the mechanical performance. Intentional deviation from a flat joint plane was introduced in different bond angles (0°, 60°, 90° and 120°) and the joints were subjected to a quasi-static tensile load. Comparisons were made regarding the mechanical behavior of the conventional flat joint and the wavy joints. The visible failure modes that occurred within each of the joint configurations was also highlighted and explained. Load vs. displacement graphs were produced and compared, as well as the failure modes discussed both visually and qualitatively. It was observed that distinct interface morphologies result in variation in the load–displacement curve and damage types. The wavy-lap joints experience a considerably higher displacement due to the additional bending in the joint area, and the initial damage starts occurring at a higher displacement. However, the load level had its maximum value for the single-lap joints. Our findings provide insight for the development of different interface morphology angle variation to optimize the joints behavior, which is widely observed in some biological systems to improve their performance.

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