Short-Fiber-Reinforced Polymeric Composites: Structure-Property Relations

Short-fiber-reinforced polymeric composites are an extremely useful class of heterogeneous materials that can be produced from a wide variety of materials and using a wide variety of manufacturing processes. The local inhomogeneity and variability of the material produces difficulties in the prediction of effective composite properties and in the prediction of the sensitivity of those properties to variations in the constituent volume fractions, properties, and morphology. To avoid costly testing programs, models have been developed which enable efficient composite property prediction. In this article, the description of fiber orientation and its prediction and measurement is summarized. A summary is given for three major methods of composite property prediction: the laminate analogy employing the Halpin-Tsai empirical model, the prediction of unidirectional fiber properties using an inclusion method followed by an orientation averaging procedure, and numerical solutions using the finite element method. A brief discussion is given of the effect of fiber length distribution, the “skin-core” effect, and three-phase systems such as those found in typical automotive applications. Most of the emphasis of this article is placed on the prediction of thermomechanical properties, although a short summary of strength properties via the use of fiber efficiency factors is included.