Composite Tank Research Articles

Analysis of a hybrid composite tank under pressure

In this work, the analysis of a hybrid composite tank of storage of hydrogen is presented. This solution made of a carbon/epoxy envelope coated on a metal liner and an intermetallic material is proposed. Each layer of the laminate is assumed to be anisotropic, and liner and intermetallic were assumed to be isotropic. This work is concerned with the study of the elastic behaviour of this solution. Based on the three-dimensional (3-D) elasticity, an exact solution for the stresses, strain and displacement is presented. The effect of stacking sequences on the behaviour of hybride solution is presented.

An Initial and Progressive Failure Analysis for Cryogenic Composite Fuel Tank Design

Thermal residual stresses, internal pressure stresses, and acceleration stresses during launch were evaluated and quantified for cryogenic composite fuel tank design. Both failure initiation and progression of graphite/epoxy laminate system (IM7/977-2) [0/90/90/0/0/90]s and graphite/BMI laminate system (IM7/5250-4) [0/90/90/0/0/90]s were investigated using the non-isothermal classical laminate and plate theory (CLPT) and the maximum stress failure criterion. The thermal residual stresses in the transverse direction are the dominant stresses on each ply in the launch stage. After initial ply cracking, through-the-thickness temperature change of a laminate related to fuel leakage as well as a laminate stiffness matrix change was applied to the progressive failure analysis. The fuel leakage-based progressive analysis shows a higher number of initial ply cracking does not necessarily mean a higher chance of matrix cracking in all plies. The graphite/BMI laminate has such an advantage as transverse thermo-mechanical resistance over the graphite/epoxy laminate at an initial exposure to —253°C and 1500 kPa. In terms of complete laminate matrix cracking, however, the graphite/ epoxy laminate is more resistant to transferring stresses to other plies than the graphite/BMI laminate.

Global underground: the state of composite storage tanks

Reinforced plastic underground storage tanks (USTs) have been in use since the 1960s as an alternative to steel. Vicki P. McConnell examines international technology upgrades to composite USTs and emerging market opportunities.

Haptoglobin and serum amyloid A in relation to the somatic cell count in quarter, cow composite and bulk tank milk samples

Milk somatic cell count (SCC) is the gold standard in diagnosis of subclinical mastitis, and is also an important parameter in quality programmes of dairy cooperatives. As routine SCC analysis is usually restricted to central laboratories, much effort has been invested in the search for alternative biomarkers of mastitis and milk quality, including the presence in the milk of the acute phase proteins (APP), haptoglobin (Hp) and serum amyloid A (SAA). The aim of this study was to investigate relationships between Hp, SAA and SCC in quarter, cow composite, and bulk tank milk samples. Cows (n=165), without any clinical signs of disease or abnormalities in the milk or udder, from three different dairy farms, were used. Cow composite milk samples from all cows delivering milk at the sampling occasion were taken once in each herd. In one of the farms, representative quarter milk samples (n=103) from 26 cows were also collected. In addition, bulk tank milk samples from 96 dairy farms were included in the study. Samples were analysed for Hp, SAA and SCC, and relationships between the parameters were evaluated at quarter, cow and tank milk levels using Chi-square analysis. Milk samples were categorized according to their SCC, and the presence, or no presence, of SAA and Hp, based on the detection limits of the screening methods (0.3 mg/l and 1.0 mg/l for SAA and Hp, respectively). Hp and SAA were found in milk at quarter, cow composite and bulk tank levels. A large proportion (53%) of the animals had detectable milk concentrations of APP, and SAA was detected more frequently, and at higher concentrations than Hp, regardless of sample type. SAA was detected in as many as 82% of the bulk tank milk samples. Significant relationships were found between Hp, SAA and SCC at quarter and cow composite milk levels, but only between SAA and SCC at bulk tank milk level. Detectable levels of APP were more common at high SCC.

Strain Monitoring and Damage Detection of a Filament Wound Composite Pressure Tank Using Embedded Fiber Bragg Grating Sensors

Composite pressure tanks are rapidly expanding in their range of use. However, for high pressure flammable or toxic gases, there is less confidence about their reliability. In this study, fiber Bragg grating (FBG) sensors embedded into a composite pressure tank monitored strain and detected damage. The sensor heads and fiber optic lines were protected with an acrylate recoating, adhesive films, PVC tubes and Teflon film to survive under the harsh environment of the filament winding process. During the quasi-static loading test, the internal strain was measured with embedded FBG sensor arrays. In order to detect damage occurred during the test, impacts were applied on three different positions in each side by an impact hammer. The difference between damaged and undamaged sides in impact response was analyzed. An interrogation system using a wavelength-swept fiber laser (WSFL) was used for measuring strain, and an erbium-doped fiber amplifier (EDFA) laser source with a tunable Fabry-Perot filter was used for measuring impact response.

Matrix Crack Detection of CFRP Laminates in Cryogenic Temperature Using Electrical Resistance Change Method

For a cryogenic fuel tank of a next generation rocket, a Carbon Fiber Reinforced Plastic (CFRP) laminated composite tank is one of the key technologies. For the fuel tank made from the laminated composites, matrix cracks are significant problems that cause leak of the fuel. In the present paper, electrical resistance change method is adopted to monitor the matrix cracking of the CFRP laminate. Previous studies show that tension load in fiber direction causes electrical resistance increase due to the piezoresistivity of the carbon fibers, and fiber breakages also cause the electrical resistance increase of the CFRP laminates. In order to distinguish the electrical resistance changes due to matrix cracking from those due to the piezoresistivity and the fiber breakages, residual electrical resistance change under the complete unloading condition is employed in the present study. Experimental investigations were performed using cross-ply laminates in cryogenic temperature. As a result, it can be revealed that the residual electrical resistance change is a useful indicator for matrix crack monitoring of the cross-ply CFRP laminates.

On-board Strain Measurement of a Cryogenic Composite Tank Mounted on a Reusable Rocket using FBG Sensors

This article presents the real-time strain measurement of a composite liquid hydrogen (LH2) tank using fiber Bragg grating (FBG) sensors. The tank was composed of carbon fiber reinforced plastic (CFRP), and an aluminum liner was fabricated by the filament winding method and mounted on a reusable rocket. This rocket (vertical takeoff and landing) is called a reusable rocket vehicle test (RVT) and was developed by the Institute of Space and Astronautical Science of the Japan Aerospace Exploration Agency (ISAS/JAXA). Considering the high operational pressure and the iterative use of the tank, its structural integrity must be guaranteed. Thus, the authors have attempted a real-time strain measurement of the composite LH2 tank using FBG sensors during rocket operations. First, the adhesive properties of the FBG sensors were investigated at cryogenic temperatures. As a result, UV-coated FBG sensors and polyurethane adhesives were adopted. An onboard FBG demodulator was then developed to be mounted on the rocket and its performance was assessed. Finally, the strain measurement was attempted during the flight experiments of the RVT using the onboard FBG demodulator. FBG sensors were glued on the surface of the composite LH2 tank and connected to the onboard FBG demodulator. During these rocket operations, the output of the onboard FBG demodulator was continuously monitored via a telemetry system. The results obtained by the demodulator agreed well with those of the conventional foil strain gage.

Micromechanical Analysis of Composite Laminates at Cryogenic Temperatures

A finite element analysis-based micromechanics method is developed to investigate development of microcracks in a graphite/epoxy composite liquid hydrogen tank at cryogenic temperatures. The unit cell of the composite is modeled using finite elements. Periodic boundary conditions are applied to the boundaries of the unit cell. The temperature-dependent properties including the coefficient of thermal expansion of the matrix material are taken into account in the analysis. The thermoelastic constants of the composite are calculated as a function of temperature. The stresses in the fiber and matrix phases and along the fiber-matrix interface are calculated. When the laminated composite structure is subjected to combined thermal and mechanical loads, the macrostrains are computed from the global analysis. Then, the macrostrains and temperatures are applied to the unit cell model to evaluate microstresses, which are used to predict the formation of microcracks in the matrix. The method is applied to a composite liquid hydrogen storage system. It is found that the stresses in the matrix phase could be large enough to cause microcracks in the composite.

The study on compatibility of polymer matrix resins with liquid oxygen

Liquid oxygen (LOX) polymer composite tank is very important in the development of next generation of launch vehicles. To study LOX compatible polymeric matrix resins, three kinds of epoxy resins were studied. LOX impact test was used to evaluate polymers’ compatibility with LOX. Thermogravimetric analysis was used to analyze polymers’ oxidation. It seemed that polymers with better anti-oxidation properties, characterized by lower oxidation weight gain, lower weight loss and lower flash point, behaved better LOX compatibility. Fourier transform infrared attenuated total reflection spectroscopy confirmed the chemical reactions during the LOX impact process on the surface of polymers were similar to the oxidation reaction in gaseous oxygen (GOX) at high temperatures, which indicated the chemical mechanism of LOX compatibility of polymers was just oxidation reaction. In this way, two new epoxy resins with desirable LOX compatibility were acquired by modification.

Matrix crack detection of CFRP using electrical resistance change with integrated surface probes

For the cryogenic tanks of next generation reusable launching vehicles, the laminated composite tank is one of the key technologies. For composite fuel tanks made from laminated carbon fibre reinforced polymers (CFRP), matrix cracking is a significant problem that may cause fuel leakage. In the present paper, an electrical resistance change method with integrated probes on a single side of the surface of a CFRP composite structure is adopted to detect the matrix cracking of the laminated composites. For a fuel tank structure made of a CFRP laminate, we cannot mount electrical probes on the end of structure or on the inside of the tank structure. We have to mount all probes only on the outside surface. The present method used finite element analyses (FEA) to search for the best placement of probes for matrix crack detection using a rectangular plate. To simulate the tank structure, all probes are placed on a single surface of the CFRP plate specimen. The present study adopted a four-probe method for measuring the electrical resistance change. The FEA revealed that the electrical resistance increases linearly with increase in the number of matrix cracks inside of the probes. By means of thin CFRP cross-ply laminate, the method was experimentally confirmed to be useful for detecting matrix crack density between the probes. Residual electrical resistance at the completely unloaded condition increased with increase in matrix crack density. Measurements of the residual electrical resistance enabled us to detect the matrix crack density without loading.

Overview of trends in advanced composite research and applications in Japan

Recent research activities in advanced composites technologies conducted in Japan are reviewed and introduced. New research topics in reinforcing fibers described are low modulus pitch-based carbon fiber and PBO fiber. The second of these is very topical at the present time: nano-technology based composites use materials such as carbon nanotube, or carbon nano-fiber, or nanoclay. Because the Composites Technology Center in the Japan Aerospace Exploration Agency (JAXA) leads many new research fields in composites, the present review paper shows a slight bias towards the outputs of JAXA. The most remarkable outcome in this field at present is a compression strength improvement by loading cup-stack type carbon nano-fiber (CSCNF). Prepreg containing this CSCNF has been developed and has already been rerleased into the market. The third topic is related to newly developed high performance polymers including heat resistant polyimide, Tri A-PI and its family. The most recent product is a heat resistant polyimide that is highly soluble in some organic solvents; this material is suitable for preparation of imide wet prepreg. Composites fabricated through this prepreg route exhibit no voids and defects compared to the traditional amid-acid polyimide prepreg route. Another new topic in polymers is related to Japan's national project, radiation cure polymers and their processing. Electron beam cure, ultra-violet cure and visual light cure resins and their processing technologies have been developed in this national project. The next topic is a development of the low cost composites technology mainly for aircraft components. JAXA's activities related to this field are introduced first based on two new key technologies — Z-anchor® and stitching. New findings about the mechanism of interlaminar reinforcement by stitching are slightly focused. Finally, remarkable theoretical findings about composite mechanics in recent years are described. A clarification of mechanics of compression after impact behavior by using a newly developed cohesive zone element is reviewed first in this category. Matrix crack growth theories in the laminae adjacent to the initially cracked layer are introduced next where a motivation of this research is a cryogenic composite tank for future space transportation systems. The final topic is a development of the theory of structural health monitoring by using small diameter FBG sensor. By an evolution of these theories structural health monitoring has almost reached the level of practical applications.

Through-Thickness Connection of Matrix Cracks in Laminate Composites for Propellant Tank

Matrix crack accumulation in multiple plies of composite laminates is experimentally investigated to assess the through-thickness connection of matrix cracks, which is closely related to propellant leakage problems of composite tanks. Cracking patterns in [0/θ 2 /90] s laminates reveal that layup angles have a significant effect on crack induction mechanisms in contiguous plies. Matrix crack propagation behaviors in the fiber direction of θ ply induced by 90-ply cracks are investigated in terms of energy release rates using parametric-oriented finite element analysis based on an oblique coordinate system. The effect of cryogenic conditions on crack induction in contiguous plies is also studied, and discussions on through-thickness connection of matrix cracks in composite laminates are provided.

Development and flight test of metal-lined CFRP cryogenic tank for reusable rocket

A cryogenic tank made of carbon fiber reinforced plastic (CFRP) shell with aluminum thin liner has been designed as a liquid hydrogen ( LH 2 ) tank for an ISAS reusable launch vehicle, and the function of it has been proven by repeated flights onboard the test vehicle called reusable vehicle testing (RVT) in October 2003. The liquid hydrogen tank has to be a pressure vessel, because the fuel of the engine of the test vehicle is supplied by fuel pressure. The pressure vessel of a combination of the outer shell of CFRP for strength element at a cryogenic temperature and the inner liner of aluminum for gas barrier has shown excellent weight merit for this purpose. Interfaces such as tank outline shape, bulk capacity, maximum expected operating pressure (MEOP), thermal insulation, pipe arrangement, and measurement of data are also designed to be ready onboard. This research has many aims, not only development of reusable cryogenic composite tank but also the demonstration of repeated operation including thermal cycle and stress cycle, familiarization with test techniques of operation of cryogenic composite tanks, and the accumulation of data for future design of tanks, vehicle structures, safety evaluation, and total operation systems.

Multi-continuum analysis of thermally induced matrix cracking

Matrix micro-cracking due to thermal loading is a major concern in composite cryogenic tanks because it presents permeation paths for the stored fluids and gases. Accurate prediction of composite damage due to micro-crack initiation is thus an important aspect of tank analysis and design. In the research presented, failure criteria are applied at both the composite (macro-) and constituent (micro-) scale in an effort to assess the most effective analysis techniques for predicting composite damage. Constituent scale information is developed using multi-continuum theory, a classic strain decomposition approach. Numerical predictions are correlated against experimental results.

2254 ラム波を用いた極低温複合圧力容器側壁の一次検査法(S26-2 非破壊評価とモニタリング(2),S26 非破壊評価とモニタリング)

In this study, usefulness of lamb waves generated by chirp signals for NDI was examined. The target for the inspection is wall parts of composite propellant tanks. We first studied characteristics of lamb waves propagated around delamination zone by computer simulation. Then, the damage inspection using lamb waves generated by chirp signals was conducted on the composite plates with artificial damaged zone. When the sensor is on the damaged zone, maximum amplitude became 17% of those at sound zone. On the other hand, when the damage zone was between two sensors, scattered lamb waves were monitored. Finally damage inspection system was developed by utilizing these characteristics of lamb waves.

A Fundamental Study of Detecting Delaminations in Composite Tanks by Using Lamb Waves

A Fundamental Study of Detecting Delaminations in Composite Tanks by Using Lamb Waves

The effect of matrix cracks on gas permeability through CFRP laminates

Diffusion-controlled gas permeability through CFRP laminates was experimentally investigated as fundamental research on the feasibility of composite propellant tanks. Using helium gas and a helium leak detector, through-the-thickness gas permeability in CFRP laminated tubes with or without matrix cracks was measured at room temperature. The effect of loadings on the in situ gas permeability was also clarified. It is shown that, although gas permeability through CFRP laminates increases on account of the existence of matrix cracks and tensile loadings, these effects turned out not to be crucial in comparison to the leakage through multi laminar matrix cracks, which is three or four orders higher than the diffusion-controlled permeation. These results suggest that the existence of no less than one intact layer is important for the feasibility of composite propellant tanks. Finally, a diffusion model including the combined effects of damages and loads is applied to the experimental results and a successful characterization of gas permeability is presented.

多電極を用いた電気抵抗変化によるCFRPマトリックス割れ検知(J09-1 モニタリング,J09 知的材料・構造システム)

For a cryogenic tank of a next generation RLV, a laminated composite tank is one of the key technologies. For the fuel tank made from laminated composites, matrix cracking is a significant problem that causes leak of fuel. In our previous study, an electric resistance change method was adopted to detect the matrix cracking of the laminated composites. For an actual application, this method should be adopted using multiple electrodes for the entire structure. In present study, experimental investigations were performed using cross-ply laminates with multiple electrodes that have equal spacing gauge length. As a result, it can be revealed that the local matrix cracking can be detected by means of residual electric resistance. The change of the electrical contact between an electrode and carbon fibers, however, causes the experimental error in measuring of residual electric resistance.

102 FW-CFRP複合材料製タンクの埋め込みFBGセンサを用いたヘルスモニタリング(OS 知的材料・構造システム(1))

Health monitoring technologies are very important for improving the safety and durability of composite structures. FBG sensors are candidates for sensing devices for health monitoring. In this research, small-diameter FBG sensors were embedded in CFRP layers in a filament wound composite tank. Real time strain measurement of the tank during cure process and pressure test was performed by using the wavelength shift of the reflection light from the FBG sensors. Furthermore, the detection of microscopic damages was attempted by the observation of the deformation of the reflection spectrum.

電気抵抗変化を用いたＣＦＲＰマトリックス割れの検知

For a cryogenic tank of a next generation reusable launching vehicle, a laminated composite tank is one of the key technologies. For the fuel tank made from laminated carbon fiber reinforced composites, matrix cracking is a significant problem that may cause leak of fuel. In the present paper, electrical resistance change method is adopted to detect the matrix cracking of the laminated composites. Tension load in fiber direction causes electric resistance increase, and fiber breakages also cause the electric resistance increase of the CFRP laminates. Moreover, matrix cracking must be detected before charging fuel in the tank. In order to solve these problems, residual electrical resistance under complete unloading condition is measured here. Experimental investigations were performed using cross-ply laminates, and as a result, it can be revealed that the residual electrical resistance shows rapid increase after matrix cracking. FEM analyses were also performed to clarify the mechanism of the increase of electrical resistance due to matrix cracking. Small electrical current exits in the middle 90° ply, and the matrix crack impedes the current. This causes the linear increase of electrical resistance with the number of matrix cracking.