Micromechanically Based Constitutive Models for Damage Evolution in Composite Laminates

This paper presents the mathematical modelling of fatigue damage able to carry out simulation of evolution of delamination in the laminated composite structures under cyclic loadings. A new elastic fatigue damage evolution law is proposed here. A classical interface damage evolution law, which is commonly used to predict static debonding process, is modified further to incorporate fatigue delamination effects due to high cycle loadings. The proposed fatigue damage model is identified using Fracture Mechanics tests like DCB, ENF and MMB. Simulations of delamination under fatigue loading are performed and results are successfully compared with reported experimental data on HTA/6376C unidirectional material. Delamination crack growth with variable fatigue amplitude is also performed and simulation results show that the proposed fatigue damage law can also accommodate this variable amplitude phenomenon. A study of crack tip behaviour using damage variable evolution is also carried out in this paper. Finally the effect of mesh density on crack growth is also discussed.

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A new stiffness-sensing test to measure damage evolution in solids

Scientific Reports ◽

10.1038/s41598-021-04452-9 ◽

2022 ◽

Vol 12 (1) ◽

Author(s):

Yichi Song ◽

Doneill J. Magmanlac ◽

Vito L. Tagarielli

Keyword(s):

Damage Evolution ◽

Constitutive Models ◽

Strain Curve ◽

Mechanical Tests ◽

Applied Strain ◽

Test Method ◽

Elastic Response ◽

Cfrp Laminates ◽

Wide Range ◽

Low Amplitude

AbstractWe propose and assess a procedure to measure the damage evolution in solids as a function of the applied strain, by conducting stiffness-sensing mechanical tests. These tests consist in superimposing to a monotonically increasing applied strain numerous, low-amplitude unloading/reloading cycles, and extracting the current stiffness of the specimens from the slope of the stress–strain curve in each of the unloading/reloading cycles. The technique is applied to a set of polymeric and metallic solids with a wide range of stiffness, including CFRP laminates loaded through the thickness, epoxy resins, injection-moulded and 3D printed PLA and sintered Ti powders. The tests reveal that, for all the materials tested, damage starts developing at the very early stages of deformation, during what is commonly considered an elastic response. We show that the test method is effective and allows enriching the data extracted from conventional mechanical tests, for potential use in data-driven constitutive models. We also show that the measurements are consistent with the results of acoustic and resistive measurements, and that the method can be used to quantify the viscous response of the materials tested.

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The Influence of Non-Traditional Composite Laminates on Open-Hole Tension Strength

Volume 10: Mechanics of Solids and Structures, Parts A and B ◽

10.1115/imece2007-41986 ◽

2007 ◽

Author(s):

D. P. Stone ◽

L. V. Smith ◽

A. Kothidar

Keyword(s):

Strain Field ◽

Composite Laminates ◽

Damage Evolution ◽

Adhesive Bonding ◽

Stress Concentrations ◽

Element Analysis ◽

Strain Measurements ◽

Stress Risers ◽

Open Hole ◽

Increased Strength

Composite materials are commonly used in applications with a need for increased strength or reduced weight. The composite structure is often attached using mechanical fasteners, even in cases where adhesive bonding is prevalent. The strength of the composite is typically reduced by large factors in the presence of these stress risers. The following considers the sensitivity of non-traditional layups to stress concentrations in the form of open-hole tension. The effects are described numerically and experimentally using finite element analysis and spatial strain measurements, respectively. Improvements in strength exceeding 10% from this preliminary exercise suggest that tailoring fiber orientations may have potential to minimize the effect of stress concentrations. Consideration of the strain field in the vicinity of the hole showed evidence of damage evolution within approximately 25% UTS for many of the laminates. The maximum strain failure criterion was able to describe the onset of damage or yield for the laminates considered here.

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Development of “Material Specific” Creep Continuum Damage Mechanics-Based Constitutive Equations

Volume 6: Materials and Fabrication ◽

10.1115/pvp2020-21677 ◽

2020 ◽

Author(s):

Ricardo Vega ◽

Jaime A. Cano ◽

Calvin M. Stewart

Keyword(s):

Constitutive Model ◽

Strain Rate ◽

Creep Strain ◽

Creep Deformation ◽

Damage Evolution ◽

Damage Mechanics ◽

Constitutive Models ◽

Continuum Damage Mechanics ◽

Creep Strain Rate ◽

Continuum Damage

Abstract The objective of this study is to introduce a method for creating “material specific” creep continuum damage mechanics-based constitutive models. Herein, material specific is defined as a constitutive model based on the mechanism-informed minimum creep strain rate (MCSR) equations found in deformation mechanism maps and calibrated to available material data. The material specific models are created by finding the best MCSR model for a dataset. Once the best MCSR model is found, the Monkman Grant inverse relationship between the MCSR and rupture time is employed to derive a rupture equation. The equations are substituted into continuum damage mechanics-based creep strain rate and damage evolution equations to furnish predictions of creep deformation and damage. Material specific modeling allows for the derivation of creep constitutive models that can better the material behavior specific to the available data of a material. The material specific framework is also advantageous since it has a systematic framework that moves from finding the best MCSR model, to rupture time, to damage evolution and, creep strain rate. Data for Alloy P91 was evaluated and a material specific constitutive model derived. The material specific model was able to accurately predict the MCSR, creep deformation, damage, and rupture of alloy P91.

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