Development and analysis of composite overwrapped pressure vessels for hydrogen storage

In this study, composite overwrapped pressure vessels (COPVs) for high-pressure hydrogen storage were designed, modeled by finite element (FE) method, manufactured by filament winding technique and tested for burst pressure. Aluminum 6061-T6 was selected as a metallic liner material. Epoxy impregnated carbon filaments were overwrapped over the liner with a winding angle of ±14° to obtain fully overwrapped composite reinforced vessels with non-identical front and back dome layers. The COPVs were loaded with increasing internal pressure up to the burst pressure level. During loading, deformation of the vessels was measured locally with strain gauges. The mechanical performances of COPVs designed with various number of helical, hoop and doily layers were investigated by both experimental and numerical methods. In numerical method, FE analysis containing a simple progressive damage model available in ANSYS software package for the composite section was performed. The results revealed that the FE model provides a good correlation as compared to experimental strain results for the developed COPVs. The burst pressure test results showed that integration of doily layers to the filament winding process resulted with an improvement of the COPVs performance.

Minimum 7-Year Outcomes of Dual Mobility Acetabular Cups in Total Hip Arthroplasty Patients

Modular dual mobility cups have been developed to potentially address postoperative hip instability, which can occur in nearly 20% of all revision total hip arthroplasty (THA) patients. By having a prosthetic construct that contains two points of articulation between the femoral head and liner and between the liner and shell, joint stability can be increased. The purpose of this study was to report on dual mobility cup survivorships, patient satisfaction outcomes, complications, and radiographic outcomes at a minimum 7-year follow-up. A high-volume academic surgeon performed a total of 143 consecutive dual mobility primary THAs on patients who had a minimum follow-up of 7 years (range, 7–8.5 years). The study cohort consisted of 77 females (54%) and 66 males (46%) who had a mean age of 65 years (range, 34–90 years). Aseptic, septic, and all-cause survivorship was determined by Kaplan-Meier analysis. Harris Hip Scores (HHS), postoperative complications, and radiographs were also assessed. No cup failures were observed. Overall, septic survivorship was 99.3% (95% confidence interval [CI]: 0.98–1.0) and all-cause survivorship was 98.6% (95% CI: 0.97–1.0). Two patients (1.4%) required revision surgery unrelated to the use of a modular dual mobility cup. Of these, one patient experienced femoral stem loosening and the other developed a periprosthetic infection that was treated with a two-stage revision. The mean total HHS was above 95 points at the most recent follow-up. Three patients (2.3%) experienced medical complications, including two deep vein thromboses and one for nonfatal pulmonary embolism. Radiographic evidence revealed incomplete seating of the metallic liner in one patient. Dual mobility cups were developed in an attempt to decrease the rate of instability following THA. The results from this study indicate that excellent clinical and patient-reported outcomes can be achieved at 7-year follow-up in patients who undergo THA with a dual mobility cup. Therefore, dual mobility cups appear to be an appropriate treatment option for primary THA.

Design of Compressed Natural Gas Pressure Vessel (Type II) to Improve Storage Efficiency and Structural Reliability

Type II storage vessel, which consists of a metallic liner hoop wrapped with a carbon fiber-resin composite to work at high pressure, has been widely adopted as the fuel container for compressed natural gas (CNG) vehicles. The general vessel, manufactured by welding enclosures to an open-end cylinder, shows uniform thickness throughout the whole liner, while the high pressure vessel, fabricated by the deep drawing and ironing (D.D.I) and spinning processes, has the integral junction part of cylinder with increased end thickness along the meridian direction. This study established a design method for improvement of failure resistance and inner capacity of the seamless CNG pressure vessel (Type II) through finite element analysis with consideration of thickness variation. Autofrettage pressure is used to enhance fracture performance and fatigue life of the vessel, and variations of stress behaviors in the liner and composite were analyzed during the autofrettage process. The influence of the composite on generation of compressive residual stress was investigated. In order to verify advantages of the D. D. I. and the spinning processes for structural safety at the end closure, the stress distribution considering thickness variation was compared with that with uniform thickness, and the maximum inner capacity objective satisfying structural reliability was obtained. The inner capacity of the proposed model with the ratio of major axis to minor axis, 2.2, was expanded by 4.5. Theoretical equivalent stresses were compared with those from the simulations, and the technique of FEM was verified.

Investigation of interlayer hybridization effect on burst pressure performance of composite overwrapped pressure vessels with load-sharing metallic liner

In this study, multi-layered composite overwrapped pressure vessels for high-pressure gaseous storage were designed, modeled by finite element method and manufactured by filament winding technique. 34CrMo4 steel was selected as a load-sharing metallic liner. Glass and carbon filaments were overwrapped on the liner with a winding angle of [±11°/90°2]3 to obtain fully overwrapped composite reinforced vessel with non-identical front and back dome endings. The vessels were loaded with increasing internal pressure up to the burst pressure level. The mechanical performances of pressure vessels, (i) fully overwrapped with glass fibers and (ii) with additional two carbon hoop layers on the cylindrical section, were investigated by both experimental and numerical approaches. In numerical approaches, finite element analysis was performed featuring a simple progressive damage model available in ANSYS software package for the composite section. The metal liner was modeled as elastic–plastic material. The results reveal that the finite element model provides a good correlation between experimental and numerical strain results for the vessels, together with the indication of the positive effect on radial deformation of the COPVs due to the composite interlayer hybridization. The constructed model was also able to predict experimental burst pressures within a range of 8%. However, the experimental and finite element analysis results showed that hybridization of hoop layers did not have any significant impact on the burst pressure performance of the vessels. This finding was attributed to the change of load-sharing capacity of composite layers due to the stiffness difference of carbon and glass fibers.

A Thermal-Mechanical Analysis Model for Composite Overwrapped Pressure Vessel for Hydrogen During Fast Filling

Composite overwrapped pressure vessel (COPV) is considered to be the most promising storage tank for hydrogen. Filling the COPV to high pressure within 3–5 minutes generates temperature increment due to negative Joule-Thomson coefficient and compression effect of hydrogen. This temperature increment induces a non-uniform temperature distribution in the COPV. The difference between the physical properties of inner metallic liner and outer composite will produce thermal stress. In this work a computational fluid dynamics (CFD) model is built to simulate the temperature increment during fast filling of the COPV. A three-dimensional thermal-mechanical finite element model for COPV is set up. The temperature distribution of the COPV by the CFD model is input into the thermal-mechanical model to analyze the stress distribution during the fast filling. This thermal-mechanical analysis model will provide technical support for the design of COPV.

Effect of Hydrogen Refueling Parameters on Final State of Charge

The state of charge (SOC) is a key indicator to show whether a compressed hydrogen tank meets refueling requirements, so it is worth to study effects of the refueling parameters on it. A new SOC analytical solution is obtained based on a simple thermodynamic model. By applying a mass balance equation and an energy balance equation for a hydrogen storage system, a differential equation was obtained. An analytical solution of hydrogen temperature was deduced from the solution of the differential equation, then an analytical solution of hydrogen mass was further deduced based on the analytical solution of hydrogen temperature with some mathematical modifications. By assuming the hydrogen density inside the tank is uniform, the SOC, which defined as a ratio of hydrogen density to the full-fill density, can be transformed to be the ratio of hydrogen mass to the full-fill mass. The hydrogen mass can be calculated from analytical solution of hydrogen mass, while the full-fill mass is supposed to be a constant value. The full-fill density of 35 MPa and 70 MPa tanks at 15 °C are respectively 24.0 g/L and 40.2 g/L, and if the volume of the tank is known, the full-fill mass can also be calculated. The analytical solution of SOC can be unitized to express the reference data, the contributions of inflow temperature and mass flow rate on SOC are presented for a Dynetek type III tank (40 L, metallic liner) and a Hexagon type IV tank (29 L, plastic liner). In addition, the two-parameter effect of inflow temperature and mass flow rate on SOC are presented. The Nusselt number and Reynolds number are utilized to modify the analytical model, the relationship between SOC and refueling parameters can be obtained through the method of fitting. The fittings show a good agreement. The SOC can be determined from the refueling parameters based on the model with more physical meaning. The method developed in this research can be applied to the control algorithm of refueling stations to ensure safety and efficiency.