Chihdar Charles Yang

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    Impact response and microstructural analysis of two glass/epoxy composite laminates
    (American Society of Mechanical Engineers (ASME), 1995-06) Pang, Su-Seng; Krishnappa, Sreeni; Yang, Chihdar Charles
    Low velocity impact tests were performed on two glass/epoxy (spring orientation and crossply) composite laminates. A weight drop tower tester was previously constructed to study the impact energy absorbed by a composite pipe using various impactors. In addition, this tester was used to predict the contact duration, force indentation and displacement of laminated composites due to impact with a hemispherical impactor. This study primarily focuses on the contact force of an impactor and on the response of the samples without consideration of the microscopic damage. The effect of impactor mass, two boundary conditions (clamp-free and clamped-clamped) and specimen dimension (length) on the impact response and microstructural damage were studied using the same experimental device. The resulting damaged specimens were sectioned and observed in an optical microscope. The energy levels in the two laminates were of similar magnitude but the delamination pattern and microstructural damage modes were quite different. The energy absorbed, peak force, and contact time increased with the increase in the impactor mass. The energy absorbed by similar specimens for the two boundary conditions were of similar magnitude, but the microstructural damage was different. The energy absorbed and the contact time increased with the increase in the specimen length. Conversely, the peak force and the visibility of the surface damage decreased with an increase in the specimen length. A correlation between the impact response and microstructural damage was provided. The observations were discussed in terms of rigidity of the specimen and potential damage sites.
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    Elastic-plastic analysis of adhesive-bonded single-lap composite joints under tension
    (American Society of Mechanical Engineers(ASME), 1993-07) Yang, Chihdar Charles; Pang, Su-Seng
    An analytical model of adhesive-bonded single-lap composite joints is developed to predict the stress-strain distributions with such joints under tensile loading. The First-order laminated anisotropic plate theorem is utilized to derive the governing equations of each adherend. The system of coupled governing equations are then determined through the kinematics of the adhesive layer. The adhesive is assumed elastic-plastic in shear while elastic in transverse tension to show the real applications. The solutions of the system are obtained with the Fourier cosine series and appropriate boundary conditions. Based on the developed model, the stress and strain distributions of the adherends and the adhesive can be predicted. The coupling effects between the external tension and the induced bending due to the asymmetry of composite laminates as well as the effects of transverse deformation are included in this study. The two adherends can have different dimension and material properties. The results are compared to the elastic model developed by the authors. The effects of the overlay length on the joint strength based on the maximum shear strain failure criteria are also provided.
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    Qualification of advanced composite pipe for use in fire water deluge systems on open type offshore oil platforms
    (American Society of Mechanical Engineers (ASME), 1996-07) Stubblefield, M.A.; Yang, Chihdar Charles; Pang, Su-Seng; Lea, Richard H.
    Different types of FIBERBOND pipe in the dry condition and with a butt & strap joint were subjected to a controlled fire for fire endurance evaluation. Testing adheres to a modification of the ASTM 1173-95 guideline, which simulates the development of an actual hydrocarbon fire. For a fire water deluge system, the pipe is in the dry condition approximately one to three minutes during an actual hydrocarbon fire. Preliminary testing shows that composite pipe is able to withstand this exposure to fire for the five minute duration of the test. This is achieved with modifying the chemical composition of the composite pipe and in some cases, adding an additional structural component to the overall pipe. Therefore, composite pipecould be used for the deluge fire system of an offshore oil platform.
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    Stress-strain analysis of an adhesive-bonded taper-taper joint between two composite flat plates
    (Society of Plastics Engineers (SPE), 1996-05) Helms, Jack E.; Yang, Chihdar Charles; Pang, Su-Seng
    An analytical model of a taper-taper adhesive-bonded joint between two composite flat plates has been developed using classical first-order laminated plate theory and including a correction for transverse shear deformation effects. The model was derived under the assumption of plane stress in the adherends. The model consists of eighteen first-order, coupled ordinary differential equations with non-constant coefficients. The model was solved numerically. A finite element model was also developed to verify the results of the analytical model using the COSMOS/M commercial software package.
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    Strength analysis of butt and strap joints under tension and bending
    (Society for the Advancement of Material and Process Engineering, 1990-04) Griffin, Steven A.; Pang, Su-Seng; Yang, Chihdar Charles
    The strength analysis of a butt and strap composite pipe joint is provided. This commercial joint consists of mating two sections of pipe and overwrapping them with additional composite laminae. The pipe analyzed in this study consists of four plies: resin rich liner, one ply of chopped strand mat, and two plies of filament wound glass fibers at 54 . Each lamina is a combination of vinyl ester resin and E-glass fibers. The overlays analyzed in this study are two and six plies of chopped strand mat. Mathematical expressions of the strength under tension and bending are derived using mechanics of materials along with suitable failure criterion. These expressions are in terms of stiffness and strength of each ply, and the geometry of the joint. Different failure modes are discussed and justified in the analytical model.