VTechWorks Repository :: Browsing by Author "Henneke, Edmund G. II"

Browsing by Author "Henneke, Edmund G. II"

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The accelerated characterization of viscoelastic composite materials
Griffith, William I. (Virginia Tech, 1980-04-05)
A brief review of necessary fundamentals relative to composite materials and viscoelasticity is provided. Subsequently the accelerated characterization techniques of Time Temperature Superposition and Time Temperature Stress Superposition are treated in detail. An experimental procedure for applying the latter to composites is given along with results obtained on a particular T300/934 graphite/epoxy. The accelerated characterization predictions are found in good agreement with actual long term tests. A postcuring phenomenon is discussed that necessitates thermal conditioning of the specimen prior to testing. A closely related phenomenon of physical aging is described. The effect of each on the glass transition temperature and strength is discussed. Creep rupture results are provided for a variety of geometries and temperatures for T300/934 graphite/epoxy. The results are found to compare reasonably with a modified kinetic rate theory.
Acoustic emission based control of wood drying
Honeycutt, Robert Mahone (Virginia Tech, 1991-11-29)
Drying is one of the most critical process steps in converting trees to a marketable material for use in high value wood products. The primary reasons for drying wood are to prevent biological deterioration and to improve mechanical strength and dimensional stability. The purpose of this research study was to develop an approach to the control of drying red oak lumber that monitors acoustic emission as the basis for setting environmental conditions throughout the drying process. Northern red oak (Quercus sp.) was chosen for this study because it is one of the more difficult woods grown in the United States to dry without inducing defects. This study was limited to end drying of short lengths of full sized red oak lumber.
Acoustic propagation in nonuniform circular ducts carrying near sonic mean flows
Kelly, Jeffrey J. (Virginia Tech, 1981-01-05)
A linear model based on the wave-envelope technique is used to study the propagation of axisymmetric and spinning acoustic modes in hard-walled and lined nonuniform circular ducts carrying near sonic mean flows. This method is valid for large as well as small axial variations, as long as the mean flow does not separate. The wave-envelope technique is based on solving for the envelopes of the quasiparallel acoustic modes that exist in the duct instead oÂ£ solving for the actual wave, thereby reducing the computational time and the round-off error encountered in purely numerical techniques. The influence of the throat Mach number, frequency, boundary-layer thickness and liner admittance on both upstream and downstream propagation of acoustic modes is considered. A numerical procedure, which is stable for cases of strong interaction, for analysis of nonlinear acoustic propagation through nearly sonic mean flows is also developed. This procedure is a combination of the Adams-PECE integration scheme and the singular value decomposition scheme. It does not develop the numerical instability associated with the Runge-Kutta and matrix inversion methods for nearly sonic duct flows. The numerical results show that an impedance condition can be satisfied at the duct exit and a corresponding solution obtained. The numerical results confirm that the nonlinearity intensifies the acoustic disturbance in the throat region, reduces the intensity of the fundamental frequency at the duct exit, and increases the reflections. This implies that the mode conversion properties of variable area ducts can reflect and focus the acoustic signal to the vicinity of the throat in high subsonic flows. Also the numerical results indicate that a shock develops if certain limits on the input parameters are exceeded.
Acousto-Ultrasonic Evaluation of Cyclic Fatigue of Spot Welded Structures
Gero, Brian Matthew III (Virginia Tech, 1997-08-28)
An acousto-ultrasonic approach is used to explore the damage development in tensile shear spot welds during fatigue loading. There is reasonable data to support the hypothesis that a decrease in an AU signal is indicative of the presence of an internal crack and could be used for monitoring and evaluation purposes.
Adaptive finite element simulation of incompressible viscous flow
Fithen, Robert Miller (Virginia Tech, 1993-08-05)
A finite element method is employed for solving two- and three-dimensional incompressible flows. The formulation is based on a segregated solution method. In this segregated formulation, the velocities and pressures are uncoupled and the equations for each are solved one after the other. This segregated solution method is numerically compared to the penalty method and to previous reported data to determine its validity. Next an iterative solution method which employs an element by - element data structure of the finite element method is developed. Two types of iterative methods are used. For a symmetric stiffness matrix, the conjugate gradient method is used. For an unsymmetric stiffness matrix, the bi-conjugate gradient method is used. Both iterative solution methods make use of a diagonal preconditioning method (Jacobi preconditioning). Several problems are solved using this segregated method. In two-dimensions, flow over a backward facing step and flow in a cavity are investigated. In three-dimensions, the problems include flow in a cavity at Reynolds number 100 and 1000, and flow in a curved duct. The simulation compares very well with previously reported data, where available.
Analysis and Design of Steel Deck-Concrete Composite Slabs
Widjaja, Budi R. (Virginia Tech, 1997-10-15)
As cold-formed steel decks are used in virtually every steel-framed structure for composite slab systems, efforts to develop more efficient composite floor systems continues. Efficient composite floor systems can be obtained by optimally utilizing the materials, which includes the possibility of developing long span composite slab systems. For this purpose, new deck profiles that can have a longer span and better interaction with the concrete slab are investigated. Two new mechanical based methods for predicting composite slab strength and behavior are introduced. They are referred to as the iterative and direct methods. These methods, which accurately account for the contribution of parameters affecting the composite action, are used to predict the strength and behavior of composite slabs. Application of the methods in the analytical and experimental study of strength and behavior of composite slabs in general reveals that more accurate predictions are obtained by these methods compared to those of a modified version of the Steel Deck Institute method (SDI-M). A nonlinear finite element model is also developed to provide additional reference. These methods, which are supported by elemental tests of shear bond and end anchorages, offer an alternative solution to performing a large number of full-scale tests as required for the traditional m-k method. Results from 27 composite slab tests are compared with the analytical methods. Four long span composite slab specimens of 20 ft span length, using two different types of deck profiles, were built and tested experimentally. Without significantly increasing the slab depth and weight compared to those of composite slabs with typical span, it was found that these long span slabs showed good performance under the load tests. Some problems with the vibration behavior were encountered, which are thought to be due to the relatively thin layer of concrete cover above the deck rib. Further study on the use of deeper concrete cover to improve the vibrational behavior is suggested. Finally, resistance factors based on the AISI-LRFD approach were established. The resistance factors for flexural design of composite slab systems were found to be f=0.90 for the SDI-M method and f=0.85 for the direct method.
Analysis by Meshless Local Petrov-Galerkin Method of Material Discontinuities, Pull-in Instability in MEMS, Vibrations of Cracked Beams, and Finite Deformations of Rubberlike Materials
Porfiri, Maurizio (Virginia Tech, 2006-04-27)
The Meshless Local Petrov-Galerkin (MLPG) method has been employed to analyze the following linear and nonlinear solid mechanics problems: free and forced vibrations of a segmented bar and a cracked beam, pull-in instability of an electrostatically actuated microbeam, and plane strain deformations of incompressible hyperelastic materials. The Moving Least Squares (MLS) approximation is used to generate basis functions for the trial solution, and for the test functions. Local symmetric weak formulations are derived, and the displacement boundary conditions are enforced by the method of Lagrange multipliers. Three different techniques are employed to enforce continuity conditions at the material interfaces: Lagrange multipliers, jump functions, and MLS basis functions with discontinuous derivatives. For the electromechanical problem, the pull-in voltage and the corresponding deflection are extracted by combining the MLPG method with the displacement iteration pull-in extraction algorithm. The analysis of large deformations of incompressible hyperelastic materials is performed by using a mixed pressure-displacement formulation. For every problem studied, computed results are found to compare well with those obtained either analytically or by the Finite Element Method (FEM). For the same accuracy, the MLPG method requires fewer nodes but more CPU time than the FEM.
Analysis of surface pressure and velocity fluctuations in the flow over surface-mounted prisms
Ge, Zhongfu (Virginia Tech, 2004-12-14)
The full-scale value of the Reynolds number associated with wind loads on structures is of the order of 10^7. This is further complicated by the high levels of turbulence fluctuations associated with strong winds. On the other hand, numerical and wind tunnel simulations are usually carried out at smaller values of Re. Consequently, the validation of these simulations should only be based on physical phenomena derived with tools capable of their identification. In this work, two physical aspects related to extreme wind loads on low-rise structures are examined. The first includes the statistical properties and prediction of pressure peaks. The second involves the identification of linear and nonlinear relations between pressure peaks and associated velocity fluctuations. The first part of this thesis is concerned with the statistical properties of surface pressure time series and their variations under different incident flow conditions. Various statistical tools, including space-time correlation, conditional sampling, the probability plot and the probability plot correlation coefficient, are used to characterize pressure peaks measured on the top surface of a surface-mounted prism. The results show that the Gamma distribution provides generally the best statistical description for the pressure time series, and that the method of moments is sufficient for determining its parameters. Additionally, the shape parameter of the Gamma distribution can be directly related to the incident flow conditions. As for prediction of pressure peaks, the results show that the probability of non-exceedence can best be derived from the Gumbel distribution. Two approaches for peak prediction, based on analysis of the parent pressure time series and of observed peaks, are presented. The prediction based on the parent time series yields more conservative estimates of the probability of non-exceedence. The second part of this thesis is concerned with determining the linear and nonlinear relations between pressure peaks and the velocity field. Validated by analytical test signals, the wavelet-based analysis is proven to be effective and accurate in detecting intermittent linear and nonlinear relations between the pressure and velocity fluctuations. In particular, intermittent linear and nonlinear velocity pressure relations are observed over the nondimensional frequency range fH/U<0.32. These results provide the basis for flow parameters and characteristics required in the simulation of the wind loads on structures.
Analytical Solution of two Traction-Value Problems in Second-Order Elasticity with Live Loads
Iaccarino, Gianni Luca (Virginia Tech, 2006-08-29)
We present a generalization of Signorini's method to the case of live loads which allows us to derive approximate solutions to some pure traction-value problems in finite elastostatics. The boundary-value problems and the corresponding compatibility conditions are formulated in order to determine the displacement of the system up to the second-order of approximation. In particular, we consider the case of homogeneous and isotropic elastic bodies and we solve the following two traction-value problems with live loads:(i) a sphere subjected to the action of a uniform pressure field;(ii)a hollow circular cylinder whose inner and outer surfaces are subjected to uniform pressures. Then, starting from these solutions, we suggest experiments to determine the second-order constitutive constants of the elastic body. Expressions of the second-order material constants in terms of displacements and Lame' coefficients are determined.
An axisymmetric finite element solution for elastic wave propagation through threaded connections
Land, J. George (Virginia Tech, 1996-12-19)
An axisymmetric finite element solution method is developed for axial wave propagation through a series of threaded connections in rock drills. A piston impacts axially on a string of rods held together by threaded joints and the wave propagates through these joints before reaching the bit. The energy lost in the joints limits the maximum effective depth of the drill. Several computational techniques are used to efficiently model the problem. Non-reflecting boundaries are used to numerically absorb the waves as they exit a joint. The stored waves are then re-initiated into the next joint eliminating modeling of the entire assembly of rods. The preload in the threads is modeled by shrinking the threaded sleeve onto the rods. A new dynamic relaxation damping scheme is used which starts with an undamped model and then increases the damping until the solution converges. This method converges more rapidly than the standard constant damping.
Characterization of Crazing Properties of Polycarbonate
Clay, Stephen Brett (Virginia Tech, 2000-08-03)
The purpose of this study was to characterize the craze growth behavior of polycarbonate (PC) as a function of stress level, model the residual mechanical properties of PC at various craze levels and strain rates, and determine if the total surface area of crazing is the sole factor in residual properties or if the crazing stress plays a role. To obtain these goals, a new in-situ reflective imaging technique was developed to quantify the craze severity in transparent polymers. To accomplish the goal of craze growth rate characterization, polycarbonate samples were placed under a creep load in a constant temperature, constant humidity environment. Using the new technique, the relative craze density was measured as a function of time under load at stresses of 40, 45, and 50 MPa. The craze growth rates were found to increase exponentially with stress level, and the times to 1% relative craze density were found to decrease exponentially with stress level. One exception to this behavior was found at a crazing stress of 50 MPa at which over half of the samples tested experienced delayed necking, indicating competitive mechanisms of crazing and shear yielding. The draw stress was found to be a lower bound below which delayed necking will not occur in a reasonable time frame. The yield stress, elastic modulus, failure stress, and ductility were correlated to crazing stress, relative craze density, and strain rate using a Design of Experiments (DOE) approach. The yield stress was found to correlate only to the strain rate, appearing to be unaffected by the presence of crazes. No correlation was found between the elastic modulus and the experimental factors. The failure stress was found to decrease with an increase in relative craze density from 0 to 1%, increase with an increase in crazing stress from 40 to 45 MPa, and correlate to the interaction between the crazing stress and the strain rate. The ductility of polycarbonate was found to decrease significantly with an increase in relative craze density, a decrease in crazing stress, and an increase in strain rate. The craze microstructure was correlated to the magnitude of stress during craze formation. The area of a typical craze formed at 40 MPa was measured to be more than 2.5 times larger than the area of a typical craze formed at 45 MPa. The fewer, but larger, crazes formed at the lower stress level were found to decrease the failure strength and ductility of polycarbonate more severely than the large number of smaller crazes formed at the higher stress level.
Computerized Ultrasonic Raytracing Model for C-scans of Solid Steel Bridge Pins
Parikh, Sanjiv D. (Virginia Tech, 1998-08-06)
This report describes the results of computerized ultrasonic C-scanning of solid steel bridge pins using a raytrace model. The raytrace model was developed to facilitate interpretation of data obtained from an ultrasonic C-scanning system for the Virginia Transportation Research Council (VTRC). The report discusses the reasons behind the development of the raytrace model, as well as specifications of the model, the input conditions, and the data output and visualization. The model uses as input, various "boundary" conditions of the solid steel pin with reduced diameter pin ends, as well as size and location information of a flaw or a wear groove placed within the main pin body. The model considers sound beams to be composed of rays and calculates ray reflections/conversions. This is done until the ray returns to a receiver location or is lost due to exceeding the time-of-flight. Once the model has returned with the received ray data, it uses the receiver conditions provided (transducer used, size of scanning grid, grid resolution, etc.), and calculates a 2-Dimensional C-scan image for each particular depth/time selected. Using PV-Wave visualization software, it is possible to plot the values for each depth to view a color graph. This graphical plot can then be analyzed/compared with the field C-scans to determine the closest match of a flaw or a wear groove inside the bridge pin. This helps in deciding if the condition of the pin is acceptable.
A Control System for the Reduction of Cargo Pendulation of Ship-Mounted Cranes
Masoud, Ziyad Nayif (Virginia Tech, 2000-12-04)
Ship-mounted cranes are used to transfer cargo from large container ships to smaller lighters when deep-water ports are not available. The wave-induced motion of the crane ship produces large pendulations of hoisted cargo and causes operations to be suspended. In this work, we show that in boom type ship-mounted cranes, it is possible to reduce these pendulations significantly by controlling the slew and luff angles of the boom. Such a control can be achieved with the heavy equipment that is already part of the crane so that retrofitting existing cranes would require a small effort. Moreover, the control is superimposed on the commands of the operator transparently. The successful control strategy is based on delayed-position feedback of the cargo motion in-plane and out-of-plane of the boom and crane tower. Its effectiveness is demonstrated with a fully nonlinear three-dimensional computer simulation and with an experiment on a 1/24 scale model of a T-ACS (The Auxiliary Crane Ship) crane mounted on a platform moving with three degrees of freedom to simulate the ship roll, pitch, and heave motions of the crane ship. The results demonstrate that the pendulations can be significantly reduced, and therefore the range of sea conditions in which cargo-transfer operations could take place can be greatly expanded. Furthermore, the control strategy is applied experimentally to a scaled model of a tower crane. The effectiveness of the controller is demonstrated for both rotary and gantry modes of operation of the crane. This work was supported by the Office of Naval Research under Contract #N00014-96-1-1123.
Critical angle for reflection at a liquid-solid interface in single crystals
Henneke, Edmund G. II; Jones, Gerald L. (Acoustical Society of America, 1976)
Recent investigations have utilized the measurement of the critical angle for reflection from a liquid-solid interface for determination of the elastic constants of the solid. For anisotropic media, this technique is appropriate only for certain special cases of the incident plane and reflecting surface. We discuss here the general condition for the critical angel in anisotropic media and show that for some planes in quartz, major errors may arise if one employs the usual statement of Snell's law for definition of the critical angle.
Design and analysis of a composite wire-socket attachment
Lutz, Ernst (Virginia Tech, 1994-10-15)
A detailed study of the feasibility of anchoring fiber reinforced plastic wires for civil engineering applications is presented. An experimental investigation using tensile testing machines is performed, testing anchorages of 1, 7 and 19 wires. Conventional strain gage and acoustic emission measurement techniques are used. The tests are essential in determining the failure load and failure mode. However, the experimental data alone do not provide enough information about the behavior of the anchorage to be used exclusively in the design process. The results are used to modify the design of the anchorage system. It is shown that for a successful anchorage system the choice of material for the load transfer medium is crucial. A solution is presented to overcome the high stress concentration at the load entry area of the wire into the anchor. A finite element analysis of the anchors for 1 and for 19 wires is used to assess the stress and strain fields inside the anchor, to validate the analytical model, and to determine locations of possible high stress concentrations. Three-dimensional and one-dimensional models, that utilize axisymmetry, are evaluated. The results of the numerical analysis are used to demonstrate the improvement as a result of a change in material choice or design of the anchor. It is shown that the modification of the load transfer medium results in a decrease of 30 % of the average stress level. In the analytical investigation, several common models are introduced that describe the fiber pullout behavior. Based on a recent treatment by C. H. Hsueh, a model is developed that describes the anchorage of a wire in a conical shaped socket using orthotropic materials. This model includes boundary conditions that are similar to the ones observed in the experiments. A parametric study is performed to obtain information on the ideal geometry of the anchor system. The results and predictions of the applied techniques, i. e. analytical description, finite element method and experimental investigation, are compared and contrasted. Based on the analytical, numerical and experimental results, recommendations for improving the design of the anchor system are made. Subsequently, a modified anchor system is proposed that utilizes the properties of a load transfer medium that has a variable stiffness. The inclusion of a pure resin collar and supporting wires is suggested. For a successful completion of this project, ideas are proposed and suggestions made for future work.
Detection of fiber fracture in Unidirectional Fiber Reinforced Composites using an In-Plane Fiber Optic Sensor
Cassino, Christopher Daniel (Virginia Tech, 2002-04-26)
Fiber reinforced polymers (FRP) are an efficient and inexpensive method of repairing deteriorating infrastructure. FRP sheets can be applied to spalling bridge sections and columns to prevent further deterioration and increase stiffness. However, the effect of the environment on the long-term durability of FRP and how the various damage mechanisms initiate and develop are not known. Systems for structural health monitoring are being sought as a means of managing important components in transportation systems as assets in light of modern life cycle cost concepts. This study characterizes a fiber optic sensor for use in detecting acoustic emissions (AE) in FRP. The results of AE analysis (signal amplitude, frequency spectra, MARSE, and in-plane displacement) caused by simulated fiber fracture experiments and other types of mechanical loading in FRP test coupons are reported. The applications to the development of FRP structural health monitoring systems are also discussed.
Determination of stress intensity factors for cracks emanating from holes in finite thickness plates
Gou, Shau-Fen (Virginia Tech, 1977-12-05)
The stress freezing photoelastic method is a proven technique for the estimation of stress intensity factors along crack fronts in complex three dimensional problems. Comparisons between previous photoelastic and approximate analytical results have revealed discrepancies in results for the case where the crack shape is nearly quarter circular. In the present study, the frozen stress photoelastic method was applied to such geometries with varying flaw depth. Results are compared with those of other investigators. It is concluded that the flaw growth in this problem is non-self similar due to the complexity of boundary shapes. The variation of the stress intensity factor along the crack front is also studied.
Determining the Air Void Parameters of Concrete Using Digital Image Analysis of Polarized Light Micrographs
Scott, Michael L. (Virginia Tech, 1997-04-22)
The ASTM C457 test has long been a standard used to obtain the air void parameters of concrete materials. These air void parameters provide valuable information that has been linked to the performance of concrete under conditions such as freezing and thawing cycles. The standard test procedure involves linearly traversing a cut and polished section of a concrete specimen while a technician observes it under a microscope. Chord lengths of material constituents that the technician observes along the linear traverse are recorded and later used to calculate air void parameters statistically. This procedure is long and tedious, which makes it susceptible to human error due to operator fatigue. This study proposes and implements a new test method for evaluating concrete air void parameters using an image analysis method. A polishing procedure along with a differential interference contrast microscope are used to obtain high contrast images of material constituents, which provide raw data for the image analysis method. Because of the high contrast that can be obtained, cement paste, air voids in the cement paste, and aggregate materials in the concrete can be distinguished from one another based on these images. An image analysis program has been written for this study which linearly traverses these images and records the chord lengths of material constituents in a similar way to the standard ASTM C457 test. The chord length data must be processed further, however, because features in the images can be truncated by the edge of the image. Correction calculations for this problem are implemented in the image analysis algorithm. Two specimens which have been previously tested using the standard ASTM C457 method by the Virginia Transportation Research Council, (VTRC), are used in this study. The air void parameters obtained using the new test are compared directly with the results obtained by VTRC for the two specimens. Statistical comparisons indicate that the results of the new test are indeed significant, showing the potential it has for practical implementation. There are drawbacks to the test including a long polishing procedure, but this process can be automated. The new test appears to have excellent potential for practical application, but it should be emphasized that the test has only been implemented using materials in two concrete specimens. Further study on a variety of other concrete materials would be required for implementation in a standard procedure.
The development of poly(vinylidene fluoride) piezoelectric sensors for measuring peel stresses in adhesive joints
Anderson, Gregory Lee (Virginia Tech, 1992-02-04)
Although bond-normal stresses have been shown to be responsible for the failure of most laboratory adhesive joint geometries, the measurement of these stresses has been accomplished only through the use of very sophisticated optical techniques. In order to develop a more versatile measurement technique, poly(vinylidene fluoride) film was used to develop piezoelectric stress sensors. The sensitivities of the film to normal stresses in the three principal material directions of the orthotropic film were accurately measured using a charge amplifier and a storage oscilloscope. These measured sensitivities comprised the calibration constants of the film. In order to reduce the detrimental effect on bond strength caused by embedding the low surface energy film into adhesive bondlines, surface treatment methods were investigated using contact angle studies, XPS analysis and 1800 peel and tapered double cantilever beam adhesion specimens. An acid etch using a mixture of acetic, phosphoric and nitric acids was found to greatly improve the bond strengths to an epoxy adhesive without reducing the piezoelectric activity of the film. The bond-normal stresses in both the elastomeric butt joint and the single lap shear joint were measured using the developed stress sensors. Comparison of the measured stresses with calculated values obtained from closed-form analytical solutions and finite element analysis for the stresses was excellent. The piezoelectric sensors do have several important limitations. The piezoelectric activity of the film is lost at temperatures above 100°C (210°F). Also, the sensors are only sensitive to dynamic loads. Nonetheless, the sensors provide an accurate means of measuring peel stresses in many adhesive joints of practical interest.
The effect of physical aging on the creep response of a thermoplastic composite
Hastie, Robert L. (Virginia Tech, 1991-06-26)
The effect of thermoreversible physical aging on the linear viscoelastic creep properties of a thermoplastic composite was investigated. Radel X/IM7, an amorphous composite material considered for use in the next generation high speed transport aircraft, was studied. The operating environment for the aircraft material will be near 188°C (370°F) with a service life in excess of 60,000 hours at temperature. Accurate predictions of the viscoelastic properties of the material are essential to insure that design strength and stiffness requirements are met for the entire service life. The effect of physical aging on the creep response was studied using momentary tensile creep tests conducted at increasing aging times following a rapid quench from above the glass transition temperature (Tg) to a sub-Tg aging temperature. As the aging time increased, the creep response of the material significantly decreased. The tensile creep compliance data for each aging time were fit to the empirical equation for the creep compliance D(t): D(t)-Dₒe ^{t/tₒ)m} where Dₒ, tₒ,and m are fitting parameters determined using a nonlinear fitting program based on the Levenberg-Marquardt finite difference algorithm. The short-term creep compliance curves, obtained at various aging times, were then shifted to form a momentary master compliance curve. The double logarithmic aging shift rate μ and its dependence on sub-T_g aging temperature were determined. The aging characterization process was conducted on unidirectional specimens with 0, 90, and 45 degree fiber direction orientations. This permitted the calculation of the complete principal compliance matrix for the composite material. The effect of physical aging becomes more apparent during long-term tests when creep and aging occur simultaneously. This results in a gradual stiffening and decrease in the creep response with increased time. Predictions based solely on the Time-Temperature Superposition Principle would significantly over-predict the creep response if physical aging effects were ignored. Theoretical predictions for long-term creep compliance were made using an effective time theory and compared to long-term experimental data for each fiber orientation. Finally, experimental results of a long-term test of a 30 degree fiber angle orientation specimen were compared to theoretical predictions obtained by transforming the principal compliance matrix to the 30 degree orientation.

Browsing by Author "Henneke, Edmund G. II"

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