Multicontinuum Technology (MCT)

Multicontinuum Technology (MCT) provides a unique and computationally efficient method to access information at the material constituent level during typical finite element simulation of composite structures. Not only does MCT provide a more accurate framework for homogenizing composite microstructures to produce macroscopic material properties, it also provides an accurate decomposition of finite element deformations into constituent-averaged deformations, thus providing a theoretically sound framework for predicting damage and failure at the constituent level.

Multicontinuum Technology (MCT) is an analysis technology for composite structures that decomposes averaged (continuum) stress and strain fields of a composite material into phase averaged stress and strain fields for the constituents (fiber and matrix). The additional information (continuum stresses and strains in the constituents) provides insight for understanding sources of structural level behavior, but more importantly provides a more fundamental basis for predicting initiation and progression of material damage. MCT is intended to provide accurate and efficient predictive capabilities while at the same time being numerically efficient and simple to use.

To guarantee that these constituent stress computations properly reflect the constituent properties and microstructure they are based on micromechanical models that capture all important micro-structural details. Hence, a micromechanics model, such as the model shown in Figure 1, can be used to establish the relations between composite and constituent variables. These relations can then be used to compute constituent continuum variables without the micromechanics model. Note that this permits the micromechanics model to be of high complexity since it will in no way burden the structural analysis.

As an example consider a calculation for a plate with a hole as reported by Garnich [1996]. Two different load cases illustrated in Figure 2 were analyzed. The mechanical load case was scaled to produce the same peak composite stress as for the thermal load case at the edge of the hole. Although the peak composite stresses are identical, the constituent stresses are drastically different between the two load cases as shown in Table 1. The matrix stress for the thermal load case is seen to be twice that produced by the mechanical load case. This illustrates the value of constituent level information.

Figure 1. A simple example of micromechanical modeling starting with an observed microstructure (a) that leads to an assumed representative microstructure (b) and a resulting (three dimensional) finite element micromechanics model (c).

Figure 2. Plate with hole problems used to generate results shown in Table 1.

Table 1. Plate with hole: point stress comparison for mechanical and thermal loading.