scholarly journals Anticipating the induced delamination formation in composite laminates subjected to bending loads

2021 ◽  
Author(s):  
Mohammad Bahrami ◽  
Mohsen Malakouti ◽  
Amin Farrokhabadi
Keyword(s):  
Mechanical Properties ◽  
Composite Laminates ◽  
Failure Modes ◽  
Crack Density ◽  
Micromechanical Model ◽  
Strain Energy Release ◽  
Matrix Cracking ◽  
Proposed Model ◽  
Laminate Theory ◽  
Bending Loads

In this research, the effects of induced delamination on the variation of the mechanical properties of composite laminates subjected to bending loads are investigated using a micromechanical model. For this purpose, the variation of the mechanical properties of delaminated laminates is determined using stress analysis of damaged ply and classical laminate theory (CLT) relationships. Using the proposed model and CLT, the fracture toughness due to induced delamination formation is presented in cross-ply laminates. Subsequently, the variation of strain energy release rate (SERR) is calculated in terms of crack density using analytical and finite element models to detect dominant failure modes in different crack densities. The results are compared with those of matrix cracking propagation. The results obtained by the proposed analytical model are in good agreement with those obtained by existing numerical and experimental approaches. The proposed model can be utilized to predict induced delamination formation in composite laminates subjected to bending loads.

Hygrothermal Effect on Stiffness Reduction Modeling Damage Evolution in Cross-Ply Composite Laminates

2012 ◽  
Vol 629 ◽  
pp. 79-84
Author(s):  
M. Sahnoun ◽  
D. Ouinas ◽  
N. Benderdouche ◽  
M. Bouazza ◽  
J. Viña
Keyword(s):  
Mechanical Properties ◽  
Composite Material ◽  
Composite Materials ◽  
Composite Laminates ◽  
Crack Density ◽  
Micromechanical Model ◽  
Displacement Function ◽  
Internal Layers ◽  
Stiffness Reduction ◽  
Hygrothermal Effect

An analytical model based on the displacement function of the opening of crack applied by Lundmark and Varna [26] in the internal layers to study the evolution of the decrease of stiffness in a laminate is investigated. The results of axial rigidity versus the crack density are presented for three composite materials. The influences of the temperature and moisture on the mechanical properties of composite material are highlighted. The micromechanical model of the laminates used in present study describes the degradation of the mechanical properties of composite material by the variation in the temperature and moisture. The hygrothermal effect is observed to be harmful for composite materials.

Micromechanical prediction of damage due to transverse ply cracking under fatigue loading in composite laminates

2017 ◽  
Vol 36 (5) ◽  
pp. 377-395 ◽  
Author(s):  
Bjian Mohammadi ◽  
Milad Rohanifar ◽  
Davood Salimi-Majd ◽  
Amin Farrokhabadi
Keyword(s):  
Experimental Data ◽  
Composite Laminates ◽  
Damage Mechanics ◽  
Crack Density ◽  
Strain Energy Release ◽  
Fatigue Loading ◽  
Matrix Cracking ◽  
Finite Element Software ◽  
Stiffness Reduction ◽  
The Matrix

To predict the matrix microcracking of laminated composites under fatigue loading, a novel energy based model is presented in the framework of micromechanics. For this purpose, strain energy release rate (SERR) of microcracks which had been derived previously for the whole laminate, is developed for a lamina, and then is calculated using a stress transfer-based stiffness reduction method. The advantages of the proposed method include its capability to predict the matrix cracking of general lay-ups based on the local stresses and stiffnesses of each plies separately and not being limited to a special stacking sequence. In order to predict micro-cracking propagation of composites under cyclic loading, the coefficients of the modified Paris law are extracted using the available experimental data of crack density–cycle curves. Then using multi-scale modelling and continuum damage mechanics concept, the proposed algorithm is implemented in ANSYS finite element software, as a new user defined material (Usermat). The static progress of failure on [45/−45]s laminate is simulated and the obtained results are compared with the existing experimental data in a good agreement. Finally, the results of implemented fatigue algorithm for different cross-ply laminates under different stress levels are obtained and compared with the available experimental data.

scholarly journals Moisture Absorption Effects on the Mechanical Properties of Sandwich Biocomposites with Cork Core and Flax/PLA Face Sheets

Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7295
Author(s):  
Hom Nath Dhakal ◽  
Chulin Jiang ◽  
Moumita Sit ◽  
Zhongyi Zhang ◽  
Moussa Khalfallah ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Failure Modes ◽  
Moisture Absorption ◽  
Mechanical Performance ◽  
Core Sample ◽  
Environmental Benefits ◽  
Matrix Cracking ◽  
Core Material ◽  
Poly Lactic Acid ◽  
The Core

The aim of this study was to evaluate the moisture absorption behaviour and its influence on the mechanical properties of newly developed sandwich biocomposites with flax fibre-reinforced poly-lactic acid (PLA) face sheets and soft cork as the core material. Three different types of sandwich biocomposite laminates comprised of different layup configurations, namely, non-woven flax/PLA (Sample A), non-woven flax/PLA and cork as core (Sample B) and non-woven flax/paper backing/PLA, cork as core (Sample C), were fabricated. In order to evaluate the influence of moisture ingress on the mechanical properties, the biocomposites were immersed in seawater for a period of 1200 h. The biocomposites (both dry and water immersed) were then subjected to tensile, flexural and low-velocity falling weight impact tests. It was observed from the experimental results that the moisture uptake significantly influenced the mechanical properties of the biocomposites. The presence of the cork and paper in sample C made it more susceptible to water absorption, reaching a value of 34.33%. The presence of cork in the core also has a considerable effect on the mechanical, as well as energy dissipation, behaviours. The results of sample A exhibited improved mechanical performance in both dry and wet conditions compared to samples B and C. Sample A exhibits 32.6% more tensile strength and 81.4% more flexural strength in dry conditions than that in sample C. The scanning electron microscopy (SEM) and X-ray micro-CT images revealed that the failure modes observed are a combination of matrix cracking, core crushing and face core debonding. The results from this study suggest that flax/PLA sandwich biocomposites can be used in various lightweight applications with improved environmental benefits.

NUMERICAL PREDICTION OF STIFFNESS DEGRADATION OF THIN-PLY CFRP LAMINATES UNDER FATIGUE LOADING

2021 ◽  
Author(s):  
RYOMA AOKI ◽  
RYO HIGUCHI ◽  
TOMOHIRO YOKOZEKI
Keyword(s):  
Composite Laminates ◽  
Damage Mechanics ◽  
Crack Density ◽  
Continuum Damage Mechanics ◽  
Fatigue Loading ◽  
Stiffness Degradation ◽  
Cfrp Laminates ◽  
Mechanics Model ◽  
Element Simulation ◽  
Proposed Model

This study aims to conduct a fatigue simulation for predicting the stiffness degradation of thin-ply composite laminates with several ply thicknesses. For the simulation, a fatigue evolution model of intra-laminar damage in thin-ply composite laminates considering the effect of ply thickness was proposed. The intra-laminar damage evolution was modeled using the continuum damage mechanics model and the static and fatigue evolution law were formulated by relating the transverse crack density to the damage variable. The finite element simulation using the proposed model was conducted to predict the stiffness degradation of the laminates as a function of the number of loading cycles. The simulation results show that the experimental data can be reproduced by using the proposed fatigue model.

Experimental investigation and modeling of dynamic thermomechanical behavior of 4-harness satin weave carbon/epoxy composites

2017 ◽  
Vol 31 (9) ◽  
pp. 1181-1203 ◽  
Author(s):  
Xueyao Hu ◽  
Hui Guo ◽  
Weiguo Guo ◽  
Feng Xu ◽  
Longyang Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Composite Laminates ◽  
Failure Modes ◽  
Shear Failure ◽  
Experimental Studies ◽  
Temperature Shift ◽  
Thermomechanical Coupling ◽  
Longitudinal Splitting ◽  
Wide Range

Theoretical and experimental studies on the compressive mechanical behavior of 4-harness satin weave carbon/epoxy composite laminates under in-plane loading are conducted over the temperature range of 298–473 K and the strain rate range of 0.001–1700/s in this article. The stress–strain curves of 4-harness satin weave composites are obtained at different strain rates and temperatures, and key mechanical properties of the material are determined. The deformation mechanism and failure morphology of the samples are observed and analyzed by scanning electron microscope (SEM) micrographs. The results show that the uniaxial compressive mechanical properties of 4-harness satin weave composites are strongly dependent on the temperature but are weakly sensitive to strain rate. The peak stress and elastic modulus of the material have the trend of decrease with the increasing of temperature, and the decreasing trend can be expressed as the functional relationship of temperature shift factor. In addition, SEM observations show that the quasi-static failure mode of 4-harness satin weave composites is shear failure along the diagonal lines of the specimens, while the dynamic failure modes of the material are multiple delaminations and longitudinal splitting, and with the increasing of temperature, its longitudinal splitting is more serious, but the delamination is relatively reduced. A constitutive model with thermomechanical coupling effects is proposed based on the experimental results and the increment theory of elastic–plastic mechanics. The experimental verification and numerical analysis show that the model is shown to be able to predict the finite deformation behavior of 4-harness satin weave composites over a wide range of temperatures.

Hybrid composite laminates reinforced with flax-basalt-glass woven fabrics for lightweight load bearing structures

2020 ◽  
pp. 152808372096074
Author(s):  
Mohamed A Attia ◽  
Marwa A Abd El-baky ◽  
Mostafa M Abdelhaleem ◽  
Mohamed A Hassan
Keyword(s):  
Mechanical Properties ◽  
Composite Laminates ◽  
Failure Modes ◽  
Woven Fabrics ◽  
Plane Shear ◽  
Load Bearing ◽  
Impact Properties ◽  
Basalt Glass ◽  
Interlaminar Shear ◽  
The Impact

An experimental investigation on the mechanical performance of interlayer hybrid flax-basalt-glass woven fabrics reinforced epoxy composite laminates has been performed. The tensile, flexural, in-plane shear, interlaminar shear, bearing, and impact properties of the fabricated laminates were investigated. Test specimens were fabricated using vacuum bagging process. Failure modes of all specimens were recorded and discussed. Results proved that the mechanical properties of flax-basalt-glass hybrid laminates are highly dominated by the reinforcement combinations and plies stacking sequence. Hybridizing flax fiber reinforced composite with basalt and/or glass fabrics provides an effective method for enhancing its tensile, flexural, in-plane shear, interlaminar shear, and bearing properties as well as controls the impact strength of the composite. The fabricated hybrids are found to have good specific mechanical properties benefits. Amongst the studied flax/basalt/glass hybrids, FBGs has the highest tensile properties, GBFs has the highest flexural and impact properties, and GFBs has the best shear and bearing properties. Flax-basalt-glass hybrid composites with different layering sequence seem to be an appropriate choice for lightweight load bearing structures.

Partial Strain Energy Release Rate for Study Matrix Cracking Evolution in Composite Cross-Ply Laminates

2015 ◽  
Vol 24 (3) ◽  
pp. 096369351502400
Author(s):  
Jean-Luc Rebière
Keyword(s):  
Stress Field ◽  
Composite Laminates ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Matrix Cracking ◽  
Damage State ◽  
Damage Process ◽  
Cracking Mechanisms ◽  
Observed Damage

Matrix cracking is generally the first observed damage in composite laminates. The stress field distribution in the damaged cross ply laminates is analysed through an approach which uses several hypotheses to simplify the damage state. The proposed cracking criterion involves the respective partial part of the 0° and 90° layers to the damage process. The initiation of transverse and longitudinal cracking mechanisms is predicted.

Evolution of Crack Density in Cross-Ply Laminates - Application of a Coupled Stress and Energy Criterion

2016 ◽  
Vol 713 ◽  
pp. 262-265
Author(s):  
Maria Kashtalyan ◽  
I.G. García ◽  
Vladislav Mantič
Keyword(s):  
Composite Laminates ◽  
Crack Density ◽  
Great Influence ◽  
Energy Criterion ◽  
Matrix Cracking ◽  
Transverse Cracks ◽  
Transverse Cracking ◽  
Finite Fracture Mechanics ◽  
Equivalent Constraint Model ◽  
Constraint Model

The first damage mode to appear in continuous fibre-reinforced composite laminates subjected to in-plane loading is usually transverse cracking, i.e. matrix cracking in the off-axis plies of the laminate. Since the density of transverse cracks has a great influence on the subsequent failure steps like delaminations, it is important to be able to predict it accurately. In this paper, the evolution of crack density with increasing external load is predicted using a combination of the Coupled Criterion of Finite Fracture Mechanics and the Equivalent Constraint Model.

Property Degradation of Anisotropic Composite Laminates with Matrix Cracking. Part 1: Development of Constitutive Relations for (θm/90n)s Cracked Laminates by Stiffness Partition

1996 ◽  
Vol 15 (11) ◽  
pp. 1149-1160 ◽  
Author(s):  
Hua Yu ◽  
Wang Xingguo ◽  
Li Zhengneng ◽  
He Qingzhi
Keyword(s):  
Composite Laminates ◽  
Constitutive Relations ◽  
Crack Density ◽  
Matrix Cracking ◽  
Normal Response ◽  
Shear Response ◽  
Plane Normal ◽  
Anisotropic Composite ◽  
Stiffness Partition

The study on property degradation of damaged composite laminates is extended to anisotropic laminates with matrix cracking. In Part 1 of the paper, an idea of “stiffness partition” is proposed to deal with the puzzle that the in-plane normal response is coupled with the shear response of the laminates. For (θ m/90 n), laminates containing transversely cracked layers under general in-plane loading, the constitutive relations are derived and the effective stiffnesses are expressed as the functions of crack density.

A damage mechanics model for low-velocity impact damage analysis of composite laminates

2017 ◽  
Vol 121 (1238) ◽  
pp. 515-532 ◽  
Author(s):  
N. Li ◽  
P.H. Chen ◽  
Q. Ye
Keyword(s):  
Composite Laminates ◽  
Damage Mechanics ◽  
Failure Modes ◽  
Impact Damage ◽  
Matrix Cracking ◽  
Low Velocity Impact ◽  
Fracture Plane ◽  
Low Velocity ◽  
Velocity Impact ◽  
The Impact

ABSTRACTA method was developed to predict numerically the damage of composite laminates with multiple plies under low-velocity impact loading. The Puck criterion for 3D stress states was adopted to model the intralaminar damage including matrix cracking and fibre breakage, and to obtain the orientation of the fracture plane due to matrix failure. According to interlaminar delamination mechanism, a new delamination criterion was proposed. The influence of transverse and through-thickness normal stress, interlaminar shear stress and damage conditions of adjacent plies on delamination was considered. In order to predict the impact-induced damage of composite laminates with more plies quickly and efficiently, an approach, which can predict the specific damage of several plies in a single solid element, was proposed by interpolation on the strains of element integration points. Moreover, the proposed model can predict specific failure modes. A good agreement between the predicted delamination shapes and sizes and the experimental results shows correctness of the developed numerical method for predicting low-velocity impact damage on composite laminates.

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