Damage evolution in fibrous composites caused by interfacial debonding

Failure mechanism of complex profile component is always different from that of conventional plate counterpart due to the coupling effect of material and structure. In this work, the low-velocity impact (LVI) and compression after impact (CAI) behaviors of Ω-shape hybrid carbon/Kevlar 3 D orthogonal woven (3DOW) composite made for vehicle B-pillar were comprehensively studied by mechanical tests and mesoscale finite element (FE) analysis at component level, high-speed infrared (IR) thermal imaging, acoustic emission (AE) detection, and microscopic damage morphology characterization. It is found that a through-thickness stress concentration ring leads to high stress state and damage zone penetrating from the impact side to non-impact side along the ring path instead of at the lowest impactor position. The slope effect can not only help the stress conduction downward, but also inhibit the damage propagation from the impact side to the slope. Impact-induced cracks are concentrated around the R corners and extended along the axial direction of the specimen, forming the strip-shaped damage concentration zone along the upper eave of the slope. The Progressive Top-Down Crushing (PTDC) mode of compression after impact is due to the complex deformation process of each yarn such as squeezing, folding and eversion in the crushing process from the top of specimen. And the Middle Indentation Fracture (MIF) mode is the result of bending instability and abrupt fracture. This work presents a reference significance for the further development of composite strengthening components in vehicle bodywork.

Section: Numerical Modelmentioning

confidence: 99%

Failure mechanism of Ω-shape 3D orthogonal woven composite component under transverse low-velocity impact and subsequent axial compression load

Pan

Wang

Zhang

et al. 2021

“…In media with continuous reinforcement (long fibres), the longitudinal behaviour (tension 11) appears to be linear elastic up to the material brittle failure due to fibres breakage. The transverse behaviour (tension 22 and/or in-plane shear 12) exhibits a more progressive degradation induced by the growth of a diffuse micro-crack network that initiates by debonding at the fibre/matrix interfaces and propagates by coalescence (Yang et al., 2020). To represent this behaviour, the constitutive model specifically developed for this type of materials (Praud, 2018; Praud et al., 2017b) is utilized to describe the response of the yarn phase.…”

Section: Local Constitutive Model For the Yarnsmentioning

confidence: 99%

Fully integrated multi-scale modelling of damage and time-dependency in thermoplastic-based woven composites

Praud

Chatzigeorgiou

Meraghni

2020

In this work, a multi-scale model established from the concept of periodic homogenization is utilized to predict the cyclic and time-dependent response of thermoplastic-based woven composites. The macroscopic behaviour of the composite is determined from finite element simulations of the representative unit cell of the periodic microstructure, where the local non-linear constitutive laws of the components are directly integrated, namely, the matrix and the yarns. The thermoplastic matrix is described by a phenomenological multi-mechanisms constitutive model accounting for viscoelasticity, viscoplasticity and ductile damage. For the yarns, a hybrid micromechanical–phenomenological constitutive model accounting for anisotropic damage and anelasticity induced by the presence of a diffuse micro-crack network is utilized. The capabilities of the overall multi-scale model are validated by comparing the numerical predictions with experimental data. Further illustrative examples are also provided, where the composite undergoes time-dependent deformations under uni-axial and non-proportional multi-axial loading paths. The multi-scale model is also employed to analyze the influence of the local deformation processes on the macroscopic response of the composite.

“…Micromechanics-informed damage models permit taking the stochastics on the microscale into account naturally, e. g., for progressive fiber breakage in fiber-reinforced composites (Ju and Wu, 2016; Wu and Ju, 2017), interfacial transition-zone effects (Chen et al., 2018), uncertainty in the elastic moduli of fiber-reinforced concrete (Liu et al., 2020), localized microcracks (Li et al., 2020) or random loading in fatigue processes (Franko et al., 2017). Another advantage concerns modeling the unilateral character of brittle damage, i. e., a different damaging behavior under tension compared to compression (Goidescu et al., 2015; Zhang et al., 2019), and accounting for interface debonding (Pupurs and Varna, 2017; Schemmann et al., 2018b; Yang et al., 2020). However, care has to be taken as homogenization and localization are incompatible (Gitman et al., 2007), in general, i.e., upon localization, the volume elements considered will not be representative for the effective mechanical behavior (Drugan and Willis, 1996; Hill, 1963; Kanit et al., 2003).…”

Section: Introductionmentioning

confidence: 99%

A convex anisotropic damage model based on the compliance tensor

Görthofer

Schneider

Hrymak

et al. 2021

This work is devoted to anisotropic continuum-damage mechanics in the quasi-static, isothermal, small-strain setting. We propose a framework for anisotropic damage evolution based on the compliance tensor as primary damage variable, in the context of generalized standard models for dissipative solids. Based on the observation that the Hookean strain energy density of linear elasticity is jointly convex in the strain and the compliance tensor, we design thermodynamically consistent anisotropic damage models that satisfy Wulfinghoff’s damage-growth criterion and feature a convex free energy. The latter property permits obtaining mesh-independent results on component scale without the necessity of introducing gradients of the damage field. We introduce the concepts of stress-extraction tensors and damage-hardening functions, implicitly describing a rigorous damage-analogue of yield surfaces in elastoplasticity. These damage surfaces may be combined in a modular fashion and give rise to complex damage-degradation behavior. We discuss how to efficiently integrate Biot’s equation implicitly, and show how to design specific stress-extraction tensors and damage-hardening functions based on Puck’s anisotropic failure criteria. Last but not least we demonstrate the versatility of our proposed model and the efficiency of the integration procedure for a variety of examples of interest.