Composite Vessels Research Articles

Temperature-dependent fracture behavior of towpreg epoxy resins for cryogenic liquid hydrogen composite vessels: The influence of polysiloxane tougheners on the resin yield behavior

In this study, a latent and tacky epoxy resin (EP) modified with siloxane core-shell-particles was developed and investigated. The use of EP as a towpreg matrix for winding of cryogenic composite vessels requires a certain toughness to resist microcracking. First, the mechanical properties at +90 °C, +22 °C, −50 °C and −196 °C were examined, with emphasis on the fracture toughness at cryogenic temperatures. Although the modulus of the resin increased dramatically, the KIC also increased by + 100% at −196 °C. Compression testing revealed that the associated yield point increased up to 500 MPa at −196 °C. The yield point of the modified resins was reduced by almost 10% which leads to easier yielding and enabling toughening mechanisms. Thus, the KIC value clearly is not the primary property that needs to be improved in cryogenics. Second, the radius of the plastic zone around the crack tip (Rp) was calculated. It decreased mathematically from 1.9 μm to 0.4 μm, due to a reduced energy dissipation resulting from a smaller spatial expansion of the plastic deformation zone. Finally, an optimum value of 3% by volume of polydimethylsiloxane was identified, demonstrating an increase of the Rp to 1.8 μm at −196 °C and proving the necessity of combinatorial methods to understand temperature-dependent failure of epoxy matrices.

Estimating the burst pressure of a filament wound composite pressure vessel using two-scale and multi-scale analyses

The influence of inescapable imperfections associated with fiber arrangement in the filament winding process on the burst pressure of a composite vessel is analyzed. Firstly, the influence of fiber packing, fiber spacing and fiber contiguity is analyzed through a two-scale analysis. Mechanical properties of the layers are estimated considering aforementioned parameters at the scale of micro and the burst pressure is estimated at the scale of macro. As the second approach, fiber-bundle crossovers and undulation arisen from filament winding process are also considered at the scale of meso. Thus, a multi-scale modeling is performed capturing micro, meso and macro scales.

Carbon Mast Structural Damage Detection Using Ultrasonic NDT Method

Glass and carbon fibers as materials have become the primary choice in the construction of smaller vessels. The advantages of these materials are good mechanical properties, they are relatively light materials that today anyone with a little knowledge can handle and also, financially speaking, they are materials that are affordable to almost everyone. One of the disadvantages is that composite materials are not homogeneous. This would mean that irregularities can be observed in the cross section of the laminate of such composite vessel or equipment. These irregularities are usually negligible because they simply belong to the property of composite materials. The problem arises when imperfections are caused by human factors or the action of some external force such as residual air in the laminate or delamination. Such imperfections during navigation can cause catastrophic damage. Although visible damage may seem small, it is very likely that there is much greater damage to the laminate that is not visible because it is located somewhere between the layers of fibers. Various methods exist for detecting such damage and imperfections, which can be invasive or non-invasive. The focus of this paper is on detecting the magnitude of damage in the laminate of the carbon mast of a racing sailboat Melges 32 using a non-invasive ultrasonic testing method. The Avenger EZ device was used for testing only.

Analysis of composite pressure vessel and composite overwrapped pressure vessel by analytical and finite elemental approach

Finite element analysis (FEA) was used to investigate the effects of different metal thicknesses on burst pressure and deformation of composite over wrapped pressure vessel (COPV) under fluid force. Low carbon steel and Carbon- epoxy had been selected as the materials for COPV. A constant fiber orientation angle had been considered. FEA results had been compared and found to be in good agreement with those obtained from analytical equations to validate the final element approach. Analysis had been extended to pure composite pressure vessels and COPV varying thickness of metal and keeping constant composite layer thickness to study the overwrapping effect. The metal layer was varied from 1 to 3 mm keeping constant composite layer thickness (3 mm). The COPV exhibited bursting strength greater than that of composite vessels considered for the analysis. The results showed that COPV with equal metal and composite layer offered the greatest bursting strength.

Validation of Selected Optical Methods for Assessing Polyethylene (PE) Liners Used in High Pressure Vessels for Hydrogen Storage

A polyethylene (PE) liner is the basic element in high-pressure type 4 composite vessels designed for hydrogen or compressed natural gas (CNG) storage systems. Liner defects may result in the elimination of the whole vessel from use, which is very expensive, both at the manufacturing and exploitation stage. The goal is, therefore, the development of efficient non-destructive testing (NDT) methods to test a liner immediately after its manufacturing, before applying a composite reinforcement. It should be noted that the current regulations, codes and standards (RC&S) do not specify liner testing methods after manufacturing. It was considered especially important to find a way of locating and assessing the size of air bubbles and inclusions, and the field of deformations in liner walls. It was also expected that these methods would be easily applicable to mass-produced liners. The paper proposes the use of three optical methods, namely, visual inspection, digital image correlation (DIC), and optical fiber sensing based on Bragg gratings (FBG). Deformation measurements are validated with finite element analysis (FEA). The tested object was a prototype of a hydrogen liner for high-pressure storage (700 bar). The mentioned optical methods were used to identify defects and measure deformations.

Impact Resistance of Fibre Reinforced Composite Railway Freight Tank Wagons

The use of fibre reinforced composite materials is one method by which the lightweighting of rail vehicles can be achieved. However, the issue of impact damage, amongst other challenges, limits their safety certification. This issue is accentuated by the high levels of loading a rail vehicle may be subjected to during service. This paper addresses the significance of pre-tension on large composite structures, specifically for a composite redesign of a pressure vessel for a freight tank wagon. Preloading was determined to be detrimental to the overall impact resistance of a large composite vessel. At 15.71 J of impact energy, there was a 22% increase in mean absorbed energy for a uniaxially loaded panel over an unloaded panel. However, there was only a 4% difference in penetration depth between uniaxial and biaxial loading. A novel finding from these results is that the effects of preloading are more profound if the loading does not act parallel to a principal fibre direction. Matrix cracking and delaminations are the most common failure modes observed for specimens under low-velocity impact and are intensified by preload.

Three-dimensional effects influencing failure in bend-free, variable stiffness composite pressure vessels

Pressure vessels enable liquids and gases to be stored and transported safely, finding pervasive use in many industries. These types of structure can be manufactured into many different shapes and from various materials to satisfy the requirements of their specific applications. Maximum allowable pressure is an important factor that should be considered carefully in the design process. Bend-free pressure vessels, that are enabled by variable stiffness composite designs, can even out in-plane stress distributions in the through-thickness direction thereby increasing overall load carrying capacity often accompanied by significant weight reduction. Bend-free composite vessels can therefore be considered to be possible candidates for the next generation of pressure vessels and therefore it is important to study their failure performance, often driven by safety reasons. In this study, the maximum allowable internal pressure is determined for bend-free ellipsoidal pressure vessels exploiting variable stiffness properties, using first-ply failure based on both Tsai-Wu and the recently proposed three-dimensional invariant-based failure criteria with performance subsequently compared against conventional constant stiffness, composite vessels. Parametric studies are then performed to provide physical insight and also to evaluate the effect of various material properties on the difference in failure load prediction found by these criteria.

Design and analysis of a pressure vessel according to EU 2014/29

Abstract In this study, the production and analysis of a composite vessel were performed. The materials selected for the design of the composite materials were glass fiber/epoxy, carbon fiber/epoxy and Kevlar fiber/epoxy material. Anti-symmetric orientation angles of (30°-30°), (45°-45°), (60°-60°) and (75°-75°) were used for each material. In the design of the vessel, the total thickness of the wall is defined as 3 mm. The containers were modeled using the SOLIDWORKS package program with the wall thickness of 10 and 20 layers. The containers modeled are then analyzed to determine maximum deformation and maximum stress by using the ANSYS WORKBENCH 14.0 package program which analyzes according to the finite element method. While making solutions, a pressure of 1.65 MPa as the test pressure of the vessel was defined as hydrostatic from the inner surface of the vessel, and von-Mises stress and total deformations were determined. As a result of this study, it has been determined that a 60°-60° orientation angle is the most appropriate design angle considering both the deformation values and maximum stress. Maximum stress in the design of composite containers was far below the flow limit and remained within acceptable limits for shape changes.

Stress–strain and burst failure analysis of fiber wound composite material high-pressure vessel

Composite material high-pressure storage vessel has been increasingly applied in the hydrogen storage industry. This study aims to establish parametric analysis of fiber wound composite vessel and investigate the stress distribution, failure mechanism as well as the burst strength. Based on the maximum strain criterion and Tsai-Wu failure criterion, the burst strength of the vessel and the failure mechanism of the cylinder segment were evaluated and studied. The stresses of the cylinder were much higher than those of the dome. The cylindrical part of the vessel is its weakest area. Matrix failure initiated at the spiral wound layer, then the accumulation of matrix failure resulted in the stiffness becoming degraded and hence fiber failure happened on the hoop wound layers. The fiber failure leaded to the ultimate failure of the vessel. The wound scheme of the outer layers also plays an important role on the load-bearing ability of the vessel. The burst strength of vessel with case-A wound was 122 MPa, while it was 91 MPa for case-B wound, about 25.4% decrease. The numerical results were compared with the burst mode studied in experiments on composite vessels and a good agreement was obtained. This study provides a theoretical foundation for safe design and utilization of composite material high-pressure vessel in the fields of hydrogen storage.

Acoustic tube models of the human vocal tract for the university classroom

Composite vessels of cylindrical tubes are often used to provide simple models of vowel formation in the human vocal tract. Already a two-tube model allows one to discuss vowel formation in the context of tube eigenmodes. In order to validate the two-tube model we use 3D printing to build a set of two single tubes and 26 two-tube composites representing different model realizations of the vocal tract. Good agreement between theory and experiment is obtained if the so-called acoustical end correction is taken into account. A better representation of human vowels requires an extension to more than two tubes; thus we took data for the construction from literature and investigate the spectra of five eight-tube models corresponding to the vowels [a:], [e:], [i:], [o:] and [u:]. The experimental work connected with the contextual applications in voice production aims to broaden the student’s conceptual understanding of tube resonances depending on the geometry in a more general manner.

Design of planar wound composite vessel based on preventing slippage tendency of fibers

The planar winding is one of technologies for manufacturing the filament wound composite pressure vessels, one unique type of the non-geodesic winding. In designing composite pressure vessels in general and planar filament wound composite vessels in particular, the most critical problem is determining the dome meridian contour. In this study, based on the netting theory, the mathematical model of the non-geodesic wound dome was built to create a premise for establishing the model of the planar wound dome. From the built mathematical model, the numerical method was utilized to draw the dome meridian profiles, simultaneously the relations between given initial parameters of the composite vessels and the slippage coefficient were established as well. Based on these relations and the non-slippage condition of the fiber, the limited ranges of initial parameters of the composite vessels were found out to create a basis for designing.

Design and analysis of a pressure vessel according to EU 2014/29

Abstract In this study, the production and analysis of a composite vessel were performed. The materials selected for the design of the composite materials were glass fiber/epoxy, carbon fiber/epoxy and Kevlar fiber/epoxy material. Anti-symmetric orientation angles of (30°-30°), (45°-45°), (60°-60°) and (75°-75°) were used for each material. In the design of the vessel, the total thickness of the wall is defined as 3 mm. The containers were modeled using the SOLIDWORKS package program with the wall thickness of 10 and 20 layers. The containers modeled are then analyzed to determine maximum deformation and maximum stress by using the ANSYS WORKBENCH 14.0 package program which analyzes according to the finite element method. While making solutions, a pressure of 1.65 MPa as the test pressure of the vessel was defined as hydrostatic from the inner surface of the vessel, and von-Mises stress and total deformations were determined. As a result of this study, it has been determined that a 60°-60° orientation angle is the most appropriate design angle considering both the deformation values and maximum stress. Maximum stress in the design of composite containers was far below the flow limit and remained within acceptable limits for shape changes.

Location Size and Orientation Effect of Semi elliptical Surface Crack on the Fracture of a Type 3 Composite Pressure Vessel using J integral Method

In this study, structural design and analysis of a type-3 composite over wrapped pressure vessel used in a military satellite propulsion system is presented. The aim is to design a composite tank lighter than all metal fuel tanks having the same volume. Moreover, necessary design stages have been revealed for similar composite over wrapped pressure vessels. ANSYS® is used to perform the stress-strain analysis of both metal and composite parts, to determine the optimum winding angle, tank Autofrettage and fracture characteristic for the metal liner considering the crack morphology. Tsai-Hill, Tsai-Wu and Hashin theories have been implemented to investigate the various failure modes of the composite vessel. Location, size and orientation angle of semi-elliptical surface crack has a pronounced effect on fracture characteristic of the liner. In fracture investigation J-integral method is used. It is foreseen that even in the most critical crack, the crack will not propagate and there will be no burst in the tank for proposed loading conditions. Numerical results are good agreement with the experimental results.

Analytical Modeling and Computer Simulation of Heat Transfer Phenomena during Hydrothermal Processing Using SOLIDWORKS<sup>®</sup>

Mathematical modeling of unit operations especially in biomaterials processing plays an important part in understanding simultaneous heat and mass transfer and fluid flow phenomena. Hydrothermal/supercritical processes are one such process which utilizes high temperature and pressure to synthesize materials for varied applications. The present study constitutes development of a model incorporating all standard transport equations and transient conditions to predict the behavior of process and thus materials upon heating to high temperature in an enclosed composite (Steel and Teflon (PFA) vessel. Commercial software package SOLIDWORKS® is employed to simulate and output is presented as animations after post-processing. Results yield very useful data and information about process; materials of construction and materials being processed which helps in optimization.

Residual Internal Pressure Strength Evaluation of Composite Vessels Subjected to Out-of-Plane Impact Loading using Plate Specimens

Residual Internal Pressure Strength Evaluation of Composite Vessels Subjected to Out-of-Plane Impact Loading using Plate Specimens

Light-weight Optimum Design of Laminate Structures of a GFRP Fishing Vessel

Approximately 90,000 ships are registered in South Korea, and about 80,000 of these ships are used in domestic shipping. Among these, 84% are small ships, such as a fishing vessels that weigh less than 20 tons and are made mostly of an FRP (Fiber Reinforced Plastics). When this fact is taken into account, the greenhouse gas emissions that are released per ton of a composite vessel are sizeable. In this study, the laminated structures of an FRP fishing vessel, many of which currently are being built in Korea, were analyzed by ISO (International Organization for Standardization) and international design rules, and the structures of the hulls are lightweight with optimum glass fiber mass content as determined by the laminate weight minimization algorithm. As a result, it was confirmed that the laminations of the vessels in accordance with the Korean rule could have 6.4% to approximately 11% more design margin compared to the requirements of ISO and other international rules. And the case study of the application of the laminate weight minimization algorithm showed the possibility of reducing the weight of the hull bottom plating by as much as about 19.32% and by as much as about 18.06% in the overall structure.

Estimated delamination of an elastic-plastic liner in a high-pressure metal composite vessel

To carry out delamination analysis in high-pressure metal composite vessels, a software approach is proposed in which the dynamic calculation algorithm is implemented in software systems. The algorithm is built on three points: the introduction of technological deviations (at the level of permissible defects), the determination of a three-dimensional stress-strain state, and a real-time solution. As a calculation program, LS-DYNA was selected in a dynamic formulation with the structure divided into 3D solid elements and unilateral constraint on the contact surface of the metal (liner) and composite shells was introduced. A geometrically and physically nonlinear problem is solved. The moment of liner delamination from the composite shell is determined by the change in the liner stress-strain state and by the liner deformable surface in time presented visually.

P2794Real-world reasons and outcomes for 1-month versus longer dual antiplatelet therapy strategies with a polymer-free biolimus A9-coated stent: insights from the all-comers FREEDOM registry

Abstract Background The LEADERS FREE trial established the favourable clinical profile of a new polymer-free biolimus A9-eluting stent (PF-BES) in patients at high bleeding risk when used with a 1-month dual anti-platelet therapy (DAPT) strategy. Purpose This is the first study evaluating real-world reasons and outcomes for a 1-month versus longer DAPT strategies following PF-BES percutaneous coronary intervention (PCI). Methods FREEDOM is an all-comers registry including all patients who underwent PCI with at least one PF-BES at 10 sites, between January 2016 and July 2018. Patients were stratified according to DAPT strategy at discharge (1-month vs >1-month). Baseline features, reasons for PF-BES as reported by the treating physician, and outcomes were compared between groups. Primary outcomes were the 390-day estimates of a patient-oriented composite endpoint (POCE: death, myocardial infarction (MI) or target vessel revascularization) and of a device-oriented composite endpoint (DOCE: cardiac death, target vessel-MI or ischemia-driven target lesion revascularization). Incidence rates were adjusted for clinically relevant factors and outcome predictors. To avoid survival bias, landmark analyses starting from 1-month post-PCI were further carried. Results Following PF-BES PCI, 328 (40.3%) patients were discharged with 1-month DAPT and 485 (59.6%) patients with longer DAPT (median 12 months, IQR 6–12 months). Patients with hypertension or on oral anticoagulation (OAT) were more likely and patients with a previous or an index MI were less likely to be discharged on 1-month DAPT. Patients prescribed with 1-month DAPT were more likely to have had a PF-BES for a LEADERS FREE high bleeding risk criterium than those with longer DAPT (90.2% vs 69.9%, p=0.001). The same association was observed when the reason for PF-BES was a planned major surgery (13.1% vs 6.2%; p=0.001) or OAC to be continued after PCI (38.7% vs 16.5%, p<0.001). Conversely, patients with planned longer DAPT were more likely to have had a PF-BES following the operator preference (2.4% vs 15.5%, p<0.001) or for a reason other than a LEADERS FREE criterium or operator preference (5.2% vs 11.3%, p<0.001). No between-groups differences in the occurrence of the primary outcomes (1-month vs >1-month DAPT: POCE 11.9% vs 13.2%, p=0.747; adj-HR 1.29 [95% CI 0.78–2.10]; DOCE: 4.8% vs 8.1%, p=0.500; adj-HR 1.01 [95% CI 0.50–2.07]) and of bleedings (any: 11.3% vs 9.4%, p=0.472; adj-HR 0.87 [95% CI 0.51–1-50]; BARC 3–5: 4.2% vs 2.2%; p=0.108; adj-HR 1.50 [95% CI 0.58–3.87]) were observed. Landmark analyses showed similar results. Conclusions In a large contemporary all-comers registry, factors reflecting the operator-perceived patient high bleeding risk were the main drivers of a very-short DAPT strategy following PF-BES PCI. We found no interaction of DAPT duration with outcomes following PF-BES PCI, an observation warranting investigation in adequately powered randomised studies.

An Analytical Method to Predict Dynamic Response of Cylindrical Composite Shells Subjected to Internal Blast Loading

Abstract The dynamic response of composite explosion containment vessels has been widely reported by experimental observations. In this study, we propose an analytical method to predict the dynamic response of open-ended cylindrical composite shells subjected to internal blast loading. The cylindrical composite shell has an out fiber composite shell with an inner steel liner, in which the outer fiber composite shell is simplified as a single elastic layer by an effective modulus in the hoop direction. Considering the impact between two layers during the dynamic response, the analytical solution for response histories of two layers could be obtained. Finite element analysis on the double-layer model is also conducted by ls-dyna. The analytical solution and the simulation result agree well, which demonstrates that the current analytical method can be employed in the design of this composite structure under blast loading.

Risk assessment for fisher’s safety in coastal composite fishing vessels

Risk assessment for fisher’s safety in coastal composite fishing vessels