Influence of Unit Cell Size and Fiber Packing on the Transverse Tensile Response of Fiber Reinforced Composites.

Royan J. D’Mello,Anthony M. Waas

doi:10.3390/ma12162565

Abstract

Representative volume elements (RVEs) are commonly used to compute the effective elastic properties of solid media having repeating microstructure, such as fiber reinforced composites. However, for softening materials, an RVE could be problematic due to localization of deformation. Here, we address the effects of unit cell size and fiber packing on the transverse tensile response of fiber reinforced composites in the context of integrated computational materials engineering (ICME). Finite element computations for unit cells at the microscale are performed for different sizes of unit cells with random fiber packing that preserve a fixed fiber volume fraction—these unit cells are loaded in the transverse direction under tension. Salient features of the response are analyzed to understand the effects of fiber packing and unit cell size on the details of crack path, overall strength and also the shape of the stress-strain response before failure. Provision for damage accumulation/cracking in the matrix is made possible via the Bazant-Oh crack band model. The results suggest that the choice of unit cell size is more sensitive to strength and less sensitive to stiffness, when these properties are used as homogenized inputs to macro-scale models. Unit cells of smaller size exhibit higher strength and this strength converges to a plateau as the size of the unit cell increases. In this sense, since stiffness has also converged to a plateau with an increase in unit cell size, the converged unit cell size may be thought of as an RVE. Results in support of these insights are presented in this paper.

Highlights

Automation of the manufacturing process of composites may well be the important cost efficiency gain in industrial applications (Beukers et al [1])
In the results presented in this paper, it is seen that the converged unit cell size possesses these attributes, and the converged unit cell size can be thought of as an Representative volume elements (RVEs)
Results have been presented for unidirectional fiber–matrix unit cells with randomly distributed fibers when loaded under transverse tension, in order to understand the effect of fiber packing and unit cell size on the mechanical properties such as transverse stiffness and transverse tensile strength

Summary

Introduction

Automation of the manufacturing process of composites may well be the important cost efficiency gain in industrial applications (Beukers et al [1]). Mass produced textile fiber performs that can be molded into near net shapes will lead to composite structures that have longer fatigue lives. There is an urgent need for robust and high fidelity computational tools that can replace costly testing associated with certification of composites for aerospace structural applications. Mechanics based models that possess the correct physics at each stage of a production cycle will be needed to ensure maturity of ICME based computational frameworks. Summary of the major challenges related to ICME of composites can be found in Arnold et al [2]

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Results

Conclusion