Fastdm4c: A Fast and Efficient Discrete Model for Composites

Abstract

The adoption of composite materials in the aerospace industry has enabled the achievement of structural performance levels and weight savings unimaginable even just twenty years ago. Yet only a fraction of the true potential of these materials has been expressed to date due to lack of high-fidelity models which has resulted in the adoption of extremely conservative designs compared to metallic counterparts. In part this is because, in contrast to high performance metallic alloys, the damaging and fracturing behaviors of composites are way more complex and difficult to simulate. Fiber reinforced composites feature many interacting mechanisms spanning several material and structural length scales, from the fiber scale of a few microns to the structural scale of a composite wing with a span of several meters. This makes the development of computational models for the design and optimization of composite structures extremely challenging due to the conflicting need of being able to capture microdamage events at the fiber scale while still being efficient enough to simulate structures that are at least six orders of magnitude larger. This work attempts to address this challenging problem by formulating a novel discrete, sub-lamina-scale model aimed at providing an effective description of damage at the microscale while maintaining computational costs comparable to continuum, homogenized formulations. In this new approach, composites are simulated as an assembly of Representative Unit Cells of roughly the same dimensions of the average distance between splitting cracks and their arrangements are designed to replicate the orthotropic behavior of the lamina. One distinct regularized strain-softening constitutive law is utilized to describe the behavior of the fibers using a new element called Discrete Fiber Model (DFM).