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Gas turbine engine blades are subjected to a centrifugal force in the radial direction and high frequency transverse excitation under operating conditions. A multiaxial loading machine was proposed in the present SBIR program to perform high-cycle fatigue testing on gas turbine engine blades. A GE F110 second stage fan blade was selected as the specimen for initial testing and design studies. The blade was modeled and analyzed using finite element analysis to determine the loading parameters required to simulate the operating conditions. These parameters were used as guidelines in designing the machine. The test frame, hydraulic components, control system, and data acquisition system have been integrated successfully into a fully functional multiaxial loading machine. The multi axial loading machine has three individual hydraulic actuators. One actuator is mounted in the vertical axis and is used to simulate the radial load on the blade. The other two actuators are mounted in the horizontal axis and are used to apply a transverse bending or torsion load to the blade at high frequencies. The multiaxial high frequency testing capability of the machine was demonstrated by running tests on trial specimen and an actual GE F110 second stage fan blade., The original document contains color images. All DTIC reproductions will be in black and white.

Molecular aspects of chemical and physical changes in adhesively bonded joints caused by absorbed moisture were investigated. The focus was on the pre-damage stage that precedes the formation of voids and microcracks. Dielectric relaxation spectroscopy was used as a non-destructive tool to characterize he molecular level changes in the adhesive when exposed to hygrothermal environments. Three adhesive types, a commercial epoxy-amine formulation (FM73U), a model epoxy formulation consisting of diglycidyl ether of Bisphenol A (DGEBA) and methylene dianiline (MDA), and a bismaleimide formulation consisting of 4,4' bismaleimidodiphenyl methane (component A) and 0,0' diallyl bisphenol (component B) were studied. Local dynamics were monitored by broad-band dielectric relaxation spectroscopy (DRS) and the changes in the chemical state of the matter were monitored by FTIR. The influence of moisture on the strength and durability of adhesively bonded joints were also investigated., Prepared in cooperation with Polytechnic Univ., The Herman F. Mark Polymer Research Inst., Brooklyn, NY.

The effort in this program was directed towards developing material processing systems that posses the mechanical properties and processing characteristic for use in flexible electronic and photonic devices. The main goal was to demonstrate the feasibility of fabricating Mach-Zehnder (MZ) switch using LD-3 NLO polymer material as core and PEDOT/PSS conducting polymer as cladding layers., Prepared in cooperation with the University of Dayton, School of Engineering, Dayton, OH.

A new scheme for a LD-3 nonlinear optical (NLO) polymer opto-electronic (OE) modulator/switch is presented in this Phase I that have an order of magnitude shorter interaction length than the conventional NLO polymer OE devices operating at TTL voltage levels. It utilized LD-3 NLO polymer as core layer and 3,4-Polyethylene-dioxythiophene (PEDOT) conductive polymer as cladding layers to realize an effective 1 micrometer separation between the electrodes. The polymer precessing and spin coating parameters were determined and optimized to produce triple stack film (cladding/core/cladding) to meet the design requirements of the Mach-Zehnder (MZ) switch. It has been demonstrated theoretically that the construction of MZ switch is possible using LD-3 NLO polymer as core and conducting polymer as cladding layers. The electro-optical coefficient of LD-3 waveguide was measured to be 5 pm/V at 790 nm when film was electrode-poled at 80 V/micrometers. The higher value of electrooptical coefficient can be achieved by using higher poling voltage in the presence of conductive cladding layers., Prepared in collaboration with Dayton Univ., Dayton, OH.

The state of the art in the stress analysis and strength prediction of adhesively bonded composite joints is presented. A generalized coordinate finite element analysis based on rectangular, cylindrical and wedge solid elements is developed and utilized for the three-dimensional analysis of composite bonded joints. The comparison of results between 2-D and 3-D bonded joint analysis tools are made and their limitations are discussed. Further, the submodeling technique available in the commercial finite element package ABAQUS is explored to study the three-dimensional stress field in the vicinity of joint edges and debond cracks. The series of bolted joint design codes BONJO developed by Lockheed are incorporated into a PC based Bolted and Bonded Joint (BBJ) design methodology. The Bolted and Bonded Joint design tool is made more informative and user-friendly through the use of Windows 95TM based Graphic User Interfaces (GUIs) fully integrated with a material database and on-line help.

The absence of a unified, tractable model to predict the elastic response of a multi-layered laminate (say 100 layers) has foiled attempts to understand the failure modes of practical composite structures. Global models, which follow from an assumed displacement field and lead to the definition of effective (or smeared) laminate moduli, are not sufficiently accurate for stress field computation. On the other hand, local models, in which each layer is represented as a homogeneous anisotropic continuum, become intractable as the number of layers becomes even moderately large (approximately 10). In this work, we blend these concepts into a self-consistent model which can define detailed response functions in a region of interest (local), while representing the remainder of the domain by effective properties (global). In this investigation the laminate thickness is divided into two parts. A variational principle has been used to derive the governing equations of equilibrium. For the global region of the laminate, potential energy has been utilized, while the Reissner functional has been used for the local region. The field equations are based upon an assumed thickness distribution of stress components within each layer of the local region and displacement components in the global region. The derived boundary of the global region and the prescribed tractions (pointwise in an elasticity sense) satisfy the conditions of vanishing resultant force and moment identically. The same conditions are satisfied in the local region.

Modulus components, compliance components, engineering constants, and their ratios and strengths for bidirectional symmetric laminates have been computed for T300/5208 graphite epoxy composites. These material properties are presented in graphic form as functions of either the laminate ply angle pli or the laminate angular rotation gamma. It has been found that the composites exhibit unique properties that do not have a counterpart in conventional materials. The results presented here are useful to designers for making a choice of composites for optimal performance. (Author)

Stress and strength analysis of composite laminates with a through the thickness circular hole, under uniaxial tensile load has been conducted. The hole is filled with a rigid core simulating a bolt. As a representation of the force at the bolted joint, displacement boundary conditions are applied to the rigid core. The stress analysis is based on treating the laminate as a homogeneous plate using finite element technique. The strength analysis is based on the tensor polynomial failure criterion applied to each constituent ply orientations. The ultimate laminate failure strength is based on the last ply failure stress. The resulting predictions of strength are found to be conservative as compared to experimental values. (Author)