H. F. Wu

National Institute of Standards and Technology, Maryland, United States

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Publications (3)7.02 Total impact

  • W Gu, H. F Wu, S. L Kampe, G.-Q Lu
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    ABSTRACT: The performance of fiber-reinforced composites is often controlled by the properties of the fiber–matrix interface. Good interfacial bonding (or adhesion), to ensure load transfer from matrix to reinforcement, is a primary requirement for effective use of reinforcement properties. Thus, a fundamental understanding of interfacial properties and a quantitative characterization of interfacial adhesion strength can help in evaluating the mechanical behavior and capabilities of composite materials. A large number of analytical techniques have been developed for understanding interfacial adhesion of glass-fiber-reinforced polymers. Among these techniques, the vibration damping technique has the advantage of being non-destructive as well as highly sensitive for evaluating the interfacial region, and it can allow the materials industry to rapidly determine the mechanical properties of composites. In the present study, a simple optical system was contributed for measuring the damping factor of uniaxial fiber-reinforced polymer composites in the shape of cantilever beams. The interfacial damping factors in glass-fiber-reinforced epoxy resin composites were correlated with transverse tensile strength, which is a qualitative measurement of adhesion at the fiber–matrix interface. Four different composite systems were tested in this study. In each system, three different surface treatments of glass-fiber at three different volume fractions were evaluated. The experimental results show an inverse relationship between damping contributed by the interface and composite transverse tensile strength.
    Materials Science and Engineering A 01/2000; 277(1):237-243. DOI:10.1016/S0921-5093(99)00528-6 · 2.41 Impact Factor
  • W. Gu, S. L. Kampe, G.-Q. Lu, H. F. Wu
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    ABSTRACT: Adhesion between fiber and matrix in fiber-reinforced polymer composites plays an important role both in controlling mechanical properties and in the overall performance of composites. This suggests that analytical and experimental methods to characterize the interface can be used to predict the mechanical performance of the material. To this end, vibration damping techniques have been used as a non-destructive method to evaluate interfacial effects on composites. According to the theory of energy dissipation, the quality of the interfacial adhesion can be evaluated upon separating the predicted internal energy dissipation associated with perfect adhesion from the measured internal energy dissipation of a composite system; this enables the quantification of interfacial adhesion. A micromechanics-based model for evaluating the adhesion between fiber and matrix from the damping characteristic of a cantilever beam was developed that shows an inverse relationship between the damping contributed by the interface and its adhesion strength. A simple optical system was used to measure the damping factor of unidirectional fiber-reinforced-polymer composites. Cantilever beam specimens containing either a single glass fiber or three types of single metallic wires embedded in an epoxy resin matrix were tested. A correlation was found between the measured interfacial adhesion strength directly from microbond pull-out tests and the micromechanics-based calculations from vibration damping experiments.
    Journal of Materials Science 01/1998; 33(24):5731-5737. DOI:10.1023/A:1004477309721 · 2.31 Impact Factor
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    H. F WU, W GU, G.-Q LU, S. L KAMPE
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    ABSTRACT: Adhesion at the fibre-matrix interface in fibre-reinforced composites plays an important role in controlling the mechanical properties and overall performance of composites. Among the many available tests applicable to the composite interfaces, the vibration damping technique has the advantages of being non-destructive as well as highly sensitive. An optical system was set up to measure the damping tangent delta of a cantilever beam, and the damping data in glass fibre-reinforced epoxy-resin composites were correlated with transverse tensile strength which are also a qualitative measurement of adhesion at the fibre-matrix interface. Four different composite systems containing three different glass fibre surface treatments were tested and compared. Our experimental results showed an inverse relationship between damping contributed by the interface and composite transverse tensile strength.
    Journal of Materials Science 03/1997; 32(7):1795-1798. DOI:10.1023/A:1018540420139 · 2.31 Impact Factor