Strength of Fibrous Composites

Abstract

PrefaceLaminated composites made of continuous fibers and metal, ceramic, or polymer matrices have been used for structural applications for more than half a century. Many modern industries such as aerospace engineering or wind power energy engineering would not have advanced to their current levels if composites had not been used. Among all of the superior characteristics of composites in comparison with other more traditional, isotropic structural materials, three are the most well known. They are high-specific stiffness (stiffness to mass ratio), high-specific strength and the ability to tailor desired properties by choosing suitable fiber and matrix materials as well as the fiber architecture geometry.Determination of the composite mechanical properties has attracted the attention of scientists, researchers and engineers. From an application point of view, it would be best if all of the mechanical properties of the composites can be estimated by using their constituent fiber and matrix properties and the fiber architecture parameters, i.e., by using a micromechanical approach. For the composite stiffness, this is feasible. There are many micromechanical models for efficiently estimating the effective elastic properties of laminated composites, which have been the focus of most of the available mechanics of composite materials textbooks and monographs. A very challenging problem, however, is to estimate the composite strength as well as other inelastic behaviors micromechanically. In the current literature, there is a lack of a book systematically addressing this problem. Almost all of the monographs dealing with laminate strength follow a phenomenological philosophy. Namely, the laminate strength is estimated based on the information of lamina strengths, which must be measured on composites themselves. However, predicting laminate strength micromechanically is very important, as one of the most critical issues in designing a composite structure is to know its load carrying capacity in priori. Only when this capacity has been explicitly related to the constituent properties and geometric parameters, can an optimal design choosing proper constituent materials, fiber content and architecture, and laminate layups for the structure before fabrication, be achieved.Would it be possible to dream that any mechanical property, including the ultimate load carrying capacity of a composite made using any continuous fiber architecture subjected to arbitrary loads, would be simply available without any experiment on it but be based only on an established database containing the required constituent properties? Will this become a reality? More than a decade Preface vi ago, the first author of this book established a unified micromechanical theory, the bridging model, to describe the constitutive relationship of a composite up to the point of failure. The unique feature of this theory is that the internal stresses in the constituent fiber and matrix materials of the composite under any arbitrary load conditions, including a t...

A strain-rate dependent micromechanical constitutive model for glass/epoxy composites

“…These micromechanical models were reviewed by Huang [18] and the bridging matrix model has been discussed in details. Also, he compared the bridging matrix micromechanical model with experimental results at quasi-static loading rate and with other micromechanical models to show its capabilities and accuracy.…”

“…Huang [18] modified Eshelby problem by assuming that the resulting compliance matrix of a UD composite be always symmetric and that, except for only five independent elements, all of the other elements should be dependent. In the bridging matrix micromechanical model, the elastic stress state in the matrix material ሼߪ ሽ can be correlated with that in the fiber ൛ߪ ൟ by a bridging matrix ൣ‫ܣ‬ ൧ through [30]:…”

“…The detail of the procedure for determination of the bridging matrix is discussed by Huang [18], [28][29][30]. The bridging matrix has the following general form [28]:…”

“…Micromechanics is a method to study the macroscopic response or the mechanical properties of reinforced composites based on the properties and the geometrical occupations of its constituent materials [18]. There are several researches which attempt to simulate the dynamic mechanical behavior of fibrous composites micromechanically [19][20][21][22][23].…”

“…The presented equations by bridging matrix micromechanical model for ‫ܧ‬ ଵଵ and ߥ ଵଶ are the same with the rule of mixture model equations. It has been shown that the longitudinal Young's modulus ‫ܧ(‬ ଵଵ )and Poisson's ratio (ߥ ଵଶ ) formulae are sufficiently accurate in comparison with the experimental data at static loading rate[18].…”