Development and validation of a method for linear-viscoelastic characterization of the dynamic complex modulus of short-fiber reinforced plastics using flexural resonances

Abstract

At present, the simulation cannot satisfactorily reproduce the actual vibration behavior of short-fiber reinforced plastics. This is because the required linear-viscoelastic material properties, in particular damping, are often not useable in the desired frequency range of up to 10 kHz. For this purpose, a newly reconsidered test method as an alternative to the established dynamic mechanical analysis is developed which can determine the stiffness and damping of the material for a wide frequency range, taking into account ambient conditions such as temperature and humidity as well as fiber orientation. Cuboid specimens are excited in a climatic chamber using an electromechanical shaker and their flexural vibration behavior is characterized with a laser vibrometer. Material properties can be directly determined up to a frequency of 10 kHz at constant humidity and in a temperature range from −30 °C to 200 °C. A validation is performed on specimens made out of short-fiber reinforced thermoplastic. An automotive powertrain application example is used but the test method is universally applicable for any field of activity using reinforced and non-reinforced material with sufficient stiffness for flexural vibrations in the desired frequency range.

Keywords

• Complex modulus
• Linear-viscoelasticity
• Frequency dependence
• Flexural vibration
• Short fiber