Midas NFX Material and Composite Models

Definition

The NFX material-model thread covers the elastic, nonlinear, plastic, hyperelastic, thermal, viscoelastic, laminated-composite, and composite-failure behavior described in the Midas-NFX-Analysis-Manual.

Material Families

The manual includes isotropic, orthotropic, anisotropic, and rigid elastic materials; nonlinear elastic material behavior; plastic material properties; hyperelastic behavior; thermal conductivity properties; age-independent and age-dependent viscoelasticity; and temperature-dependent material properties.

Composite Laminate Theory

For laminated composites, the source gives the classic membrane-bending relation

{N, M} = [[A, B], [B, D]] {epsilon_0, kappa}

where A, B, and D represent in-plane, coupling, and bending stiffness. The manual also includes transverse shear stiffness and thermal expansion terms for average temperature change and through-thickness temperature gradient.

Composite Failure

The composite failure section covers maximum stress, maximum strain, Tsai-Hill, Hoffman, Tsai-Wu, and NASA LaRC02 criteria. The output concepts include finite-element failure index, failure index, and strength ratio.

Solver Development Use

For a custom solver, this page points to two implementation layers: constitutive integration at integration points and laminate section integration through thickness. Composite failure should be treated as a postprocessing or damage-initiation contract unless the solver explicitly implements degradation, because a failure index alone does not define stiffness loss.

Connections

Finite Element Plasticity and Abaqus Constitutive Integration cover path-dependent material updates.
Abaqus Material Library and Data Definition and Abaqus Progressive Damage and Failure provide sibling commercial material/failure references.
Midas FEA Concrete Cracking and Material Models is a MIDAS sibling focused on civil concrete and interface material behavior.

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