Remediation of a constitutive model for ceramic composite laminates

Abstract

a b s t r a c tConstitutive models for fiber-reinforced ceramic-matrix composites (CMCs) are needed to enable implementation of these materials in future engineering systems. One such constitutive model, developed by Genin and Hutchinson [1], is based on a phenomenological description of the inelastic response of CMC laminates. Although the model has found some utility in elucidating the role of inelasticity in stress redistribution around strain concentrating features, we find that, in some instances, finite element analyses based on this model exhibit numerical convergence problems. In the present study, we demonstrate both analytically and by finite element analyses that, for certain anisotropic laminates, these numerical issues stem from the fact that the model formulation is unstable. Additionally, we propose and assess modifications to the formulation that mitigate these problems yet retain the positive features of the original model. The expectation is that the modifications will enable broader utilization of the model within the engineering design community.

An elastic–plastic constitutive model for ceramic composite laminates

“…For cross-ply laminates, a reasonable estimate for D 45 is unity [23]. ðrÞ to become large in magnitude), it is sufficient to cause significant inelasticity in shear loading, and vice versa.…”

“…For instance, the 45°tensile response is predicted to be dependent on the 0°tensile and shear responses. Here we assess the internal consistency of the in-plane stressstrain curves stemming from both the GH model for CMC laminates [2,23] and a model adapted from the work of Hahn [20] on PMC laminates. The assessment is made using the test data for SiC/SiCN described above as well as comparable data previously reported for two other CMCs: (i) a cross-ply SiC/CAS laminate [28], and (ii) a 2-D woven SiC/SiC composite [34,18].…”

“…Models of this type have been developed mainly for use with polymer matrix composites [20][21][22]. An attempt to extend the approach to CMC laminates was made by Genin and Hutchinson [2] and later expanded by Rajan and Zok [23]. For reasons elaborated upon in Section 3, however, these models are limited in applicability; that is, they presuppose a particular form of the yield/cracking surface that may be consistent with the behavior of some material systems but not others.…”

Stochastic Virtual Tests for High-Temperature Ceramic Matrix Composites

“…In one phenomenological approach, nonlinear continuum damage laws for ceramic composites are calibrated by using data from tension tests of unnotched specimens executed at two different orientations (151,152). Stresses for other specimen configurations can be predicted accurately by using the calibrated laws, provided that changes in stress components remain proportional at any point during damage evolution, which is a reasonable assumption in many cases.…”

The fibrous cellular microenvironment, and how cells make sense of a tangled web

“…are governed by local phenomena, and structural factors commonly enter the equation for phenomena occurring over length scales comparable to the sizes of a material's constituents (26,27). Engineers have harnessed this to great effect with tough ceramic composites that combine the strength of thin fibers with the toughness afforded by the stochastic failure of fiber bundles.…”