Filament-wound Cylinders Research Articles

Influence of Residual Strains on Buckling of Thin Filament-Wound Cylinders in Axial Compression

This paper describes a method for improving the accuracy of buckling predictions of thin-shell, filament-wound cylinders under axial compression loads using enhanced finite-element models. This is accomplished by incorporating the out-of-plane displacements due to residual strains, in addition to realistic stiffness coupling due to fiber undulations, into finite-element models. The out-of-plane displacements of filament-wound cylinders were scanned mechanically and incorporated into the finite-element models using a computer program. An eigenvalue buckling analysis was performed on these models. Results show that the accuracy of the buckling load prediction of the model with stiffness coupling and out-of-plane displacements due to residual strains is significantly improved compared to the case when only the stiffness coupling is incorporated into the model.

Combinatorial Optimization for Angles of Wrap in Filament Wound Cylinders

A general approximation procedure is proposed for the problem of determining optimal angles of wrap for filament wound cylinders that are under pressure, axial, or torsional loads, or under any combination of these loads. For the special cases of open-ended and close-ended cylinders under a pure pressure load, optimal solutions are presented.

Combinatorial Optimization for Angles of Wrap in Filament Wound Cylinders

Combinatorial Optimization for Angles of Wrap in Filament Wound Cylinders

Elastic response of post- and in situ consolidated laminated cylinders

This paper aims to investigate the effect of interactions between the various processing variables th application of a generalized plane deformation analysis for predicting the thermoelastic response of post-consolidated filament-wound cylinders, to post- and in situ consolidated cylinders. The theory has been enhanced significantly to model the effects of winding tension in the in situ process and the redistribution of stresses resulting from the removal of the mandrel at any point in the process. The thermal stresses resulting from post- and in situ consolidation of an IM7/PEEK cylinder are compared. The enhanced capability of the model is then used to investigate the interaction between the cylindrical part and the tool (mandrel) and also the effect of winding tension on the residual stresses in the cylinder.

A numerical and experimental study on the nonlinear behavior of laminated composite structural components

Nonlinear behavior of laminated composite plates and shells is studied. In the analysis, material nonlinearity due to the matrix degradation at the initial failure is considered along with the geometrical nonlinearity in the deformation process. An effective way of accounting the damage of the material due to initial failure is incorporated into a finite element analysis of the nonlinear behavior of the structural members. Experimental study is done on the filament-wound cylinders and laminated plates. The results are compared with the ones from the numerical analysis.

Smart Structural Composites with Monofilament, Piezoelectric Sensors

Smart materials or structures have embedded sensors to monitor their own state as well as environmental stimuli. A novel sensor was developed by sputtering a piezoelectric film onto a conductive fiber or metal wire. This sensor, similar in configuration to an optical fiber, is active since an electric field is developed when strained. Several of these sensors were embedded into a cantilevered beam and a filamentwound cylinder made from AS4/ Epon 828 composites. A variety of test cases were used to demonstrate its sensing feasibility, including free and forced vibrations and acoustic emissions.

Ultrasonic evaluation of mechanical properties of thick, multilayered, filament-wound composites

A preliminary investigation is conducted to define capabilities and limitations of ultrasonic and acousto-ultrasonic measurements related to mechanical properties of filament wound graphite/epoxy composite structures. The structures studied are segments of filament wound cylinders formed of multiple layers of hoop and helical windings. The segments consist of 24 to 35 layers and range from 3.02 to 3.34 cm in wall thickness. The resultant structures are anisotropic, heterogeneous, porous, and highly attenuating to ultrasonic frequencies greater than 1 MHz. The segments represent structures to be used for space shuttle booster cases. Ultrasonic velocity and acousto-ultrasonic stress wave factor measurement approaches are discussed. Correlations among velocity, density, and porosity, and between the acousto-ultrasonic stress wave factor and interlaminar shear strength are presented.

Micromechanics-based structural analysis of thick laminated composites

Thick filament wound cylinders, or local regions in structural laminates around cut-outs, fasteners or stiffeners may require three-dimensional (3D) analysis and evaluation, in order to fully characterize behavior and evaluate safety margins. This paper describes a particular approach to the 3D structural-level analysis of thick laminated composites that utilizes homogenization concepts and standard displacement-based finite element modeling. Hierarchical material modeling forms the basis of the procedure. The material model consists of two modules: 1. (1) a micro-model of a unidirectional lamina, containing the basic 3D constitutive information for fiber and matrix constituents 2. (2) a sublaminate model that enforces equilibrium of tractions between laminae, and delivers 3D homogenized stresses and strains and material tangent stiffnesses. This integrated approach provides the information required for evaluating damage and failure conditions at the microstructural level, and is essential for nonlinear analysis because of possible interactions between damage and failure modes. A nonlinear elastic material model is formulated, as an example; this nonlinear model, which is suitable for epoxy matrices, has been successfully implemented in a standard finite element code and used quite extensively. However, only elastic analysis results are presented, because the important characteristics of the modeling approach are clearly revealed in this setting. Comparisons are made between material model predictions and analytical, numerical, and experimental results for a unidirectional lamina, a thick laminate, and a thick cylinder under compression and bending. These results show that the accuracy of the procedure for thick laminates is quite satisfactory for practical purposes.

Influence of Local Fiber Undulations on the Global Buckling Behavior of Filament-Wound Cylinders

The predicted compressive stiffness and buckling strength of filament- wound cylinders using classical lamination theory is significantly higher than those observed experimentally. This discrepancy is partially influenced by the variation of mechanical properties in the region of fiber undulations. These regions are localized geo metric defects intrinsic to the filament-winding, weaving, and braiding processes. In the present work, the average mechanical properties of the fiber undulation region are quan tified using modified models of woven-fabric composites to account for the 3-dimensional effects. The mechanical properties thus determined can be incorporated as local element properties into global finite-element models. Preliminary results from large-displacement analyses of filament-wound cylinders are relatively more accurate when fiber undulations are accounted for.

Impact damage and residual tension strength of a thick graphite/epoxy rocket motor case

Impacters of various masses were dropped from various heights onto thick graphite/epoxy filament-wound cylinders. The cylinders represented filament-wound cases made for the booster motors of the Space Shuttle. Tups of various shapes were affixed to the impacters. Some of the cylinders were filled with inert propellant, and some were empty. The cylinders were impacted numerous times around the circumference and then cut into tension coupons, each containing an impact site. The size of the damage and the residual tension strength were measured. For hemispherical tups, strength was reduced as much as 30 percent by nonvisible damage. The damage consisted of matrix cracking and broken fibers. Analytical methods were used to predict the damage and residual tension strength. A factor of safety to account for nonvisible damage was determined. For corner and rod shaped tups, any damage that resulted in strength loss was readily visible.

Motion of Continuous Fibers through a Newtonian Resin for High Fiber Volume Fraction

This paper treats the motion of long, unidirectional, continuous fibers through a Newtonian resin. There is a consolidation force on the top row of fibers or an effective force on all the fibers due to their tension and curvature in a filament-wound cylinder. An asymptotic analysis for high fiber volume fraction is presented here. The present rigorous asymptotic solution leads to the same expressions as a previous applica tion of the lubrication approximation. The advantages of the asymptotic analysis are the definition of the error and the foundation for the proper treatment of more complex prob lems with several small parameters.

A model of filament-wound thin cylinders

A model was developed for simulating the manufacturing process of filament-wound cylinders made of a thermoset matrix composite. The model relates the process variables (winding speed, fiber tension, applied temperature) to the parameters characterizing the composite cylinder and the mandrel. The model is applicable to cylinders for which the diameter is large compared to the wall thickness. The model was implemented by a user-friendly computer code suitable for generating numerical results. The model and the corresponding code provide the following information as a function of time and position inside the composite cylinder and the mandrel during the winding and the subsequent oven curing: 1.(i) temperature throughout the cylinder and mandrel,2.(ii) degree of cure throughout the cylinder,3.(iii) viscosity throughout the cylinder,4.(iv) fiber positions,5.(v) fiber tensions,6.(vi) stresses and strains throughout the cylinder and mandrel, and7.(vii) porosity throughout the cylinder.

Twisting of Filament Wound Cylinders under Internal Pressure

Filament wound cylinders used to contain internal pressure exhibits twisting under load. This twist can give significant effect particularly when analysis requiring the axisymmetric property of the cylinder is necessary. This paper presents the significance of this twist.

Characterization of Prepreg Tow Carbon/Epoxy Laminates

Resin systems used in wet filament winding differ from those used in prepreg laminates. However it is possible to use the resins from prepreg systems in filament winding by using prepreg tows. A characterization study was carried out to investigate the matrix dominated properties of filament wound systems using AS4/3501-6 carbon/epoxy. This 3501-6 resin system is normally used in layed up prepreg laminates. The tests used were torsion combined with axial tension and compression of thin-walled tubes. The results showed the shear and cross fiber properties to be similar to those seen in layed up prepreg systems, and considerably higher than obtained with usual wet filament winding resins. Additional tests were performed on [±45]2s filament wound cylinders. Shear properties from these tests agreed well with the torsion tests at low stress levels, but were quite different at high stresses due to microcracking and state of stress effects.

An axisymmetric linear/high-order finite element for filament-wound composites-II. Evaluation on filament-wound cylinders

This paper presents an evaluation of the accuracy of an axisymmetric high-order composite element. The element is intended to be used in a design code to analyze spherical filament-wound structures. With the use of this high-order element, the computation time for a static analysis is greatly reduced when compared to that using conventional bi-linear elements. This paper presents a brief summary of the formulation used for the high-order composite element. Comparisons of the theoretical and finite element results follow for isotropic, orthotropic and filament-wound cylinders. The overall accuracy of the element is about ±3% when a sufficient integration order is chosen.

Electrothermal Curing of Filament Wound Composite Cylinders

A model was developed which describes heating of filament wound composite cylinders by applying voltage across the fibers. Two situations were examined: power applied both during and after the wind, and power applied only after completion of the wind. Electrical connections in series and in parallel were modeled. The model yields temperature and cure profiles within the laminate as functions of time during and after the filament wind process. Sample calculations were performed showing the effects of geometry and power applied on the temperature, degree of cure, and manufacture time of the cylinder. The temperature, degree of cure, and manufacture time were also calculated for a filament wound cylinder cured conventionally in an oven. Assessments were made on the merits of electrothermal curing versus curing in an oven.

ＣＦＲＰ円筒殻の圧縮座屈 Ｉ 理論解析と実験

Theoretical analysis is attemped for the effect of axisymmetrical prebuckling deformation on the compressive buckling load of anisotropic circular cylindrical shells. Compressive buckling tests of two types of filament-wound graphiteepoxy cylindrical shells and four types of laminated ones were carried out. The stacking sequences of four types of lamination are [20°, -20°, 90°], [0°, 45°, -45°, 90°], [30°, -30°, -30°, 30°, 90°, 90°] and [0°, 60°, -60°, -60°, 60°, 0°], and those of two types of filament winding are [±20°, 90°] and [90°, ±20°] where the top is inside, respectively. The calculated buckling loads of these test cylinders have disclosed the property that the prebuckling deformation raises the buckling load except for the No.3 test cylinder of which buckling mode in the linear theory is axisymmetrical. This property is contrary to the one known for isotropic cylinders. Some analytical studies are carried out for this reason. For laminated cylinders, a good agreement is observed between theoretical and experimental buckling loads. In the case of filament wound and 3- and 4-layer cylinders, after the end-shortening was removed, they returned to a perfect cylinder, as the buckling deformation was almost elastic. The buckling load of the filament-wound cylinder is lower than that of the laminated one with the same fiber direction.

Carbon filament wound cylinder and method of producing the same : Inoue, M., et al (Hitachi Chemical Company Ltd and Hitachi Ltd) US Pat 4 039 006 (2 August 1977)

Carbon filament wound cylinder and method of producing the same : Inoue, M., et al (Hitachi Chemical Company Ltd and Hitachi Ltd) US Pat 4 039 006 (2 August 1977)

Interfaces in Carbon Fiber/PyrolyticCarbon Matrix Composites

Abstract Carbon fiber/pyrolytic-carbon matrix composites contain both fiber-matrix and matrixe matrix interfaces and, thus, do not fit the usual concept of fiber-reinforced compositmaterials. This is a consequence of the chemical vapor deposition (CVD) process in which the matrix forms uniform pyrocarbon sheaths around each fiber and ultimately results in matrix-matrix interfaces with various geometries and also produces large oriented voids. The role of the fiber-matrix and matrix-matrix interfaces on the mechanical composite properties has been examined by mechanical testing and optical and scanning electron microscopy. Results will be presented for increasingly complex fibrous substrate geometries with a pyrolytic carbon matrix: single fiber, strand or yarn bundle and circumferential and angle-ply filament-wound cylinders. Data for coated single fibers demonstrate the adequacy of the fiber-matrix interface and the applicability of the rule-of-mixtures to this simple composite. The degree of utilization...

Mechanical properties of CVD carbon infiltrated carbon and graphite filament wound cylinders

Mechanical properties of CVD carbon infiltrated carbon and graphite filament wound cylinders