Fiber/matrix interface stress analysis of flax-fiber composites under transverse loading considering material nonlinearity

2020 ◽  
Vol 39 (9-10) ◽  
pp. 345-360
Author(s):  
Baris Sabuncuoglu ◽  
Onur Cakmakci ◽  
Fevzi S Kadioglu
Keyword(s):  
Fiber Composites ◽  
Flax Fiber ◽  
Material Nonlinearity ◽  
Transverse Strain ◽  
Matrix Interface ◽  
Transverse Loading ◽  
Stress Concentrations ◽  
Transverse Cracks ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

Distribution of stresses in fiber/matrix interface in UD flax fiber reinforced composites is investigated under transverse loading and compared with conventional synthetic fibers. Micro-scale finite element models with representative volume elements are generated with various fiber packing types and fiber volume ratios. The study is performed for various strain values, which take into account the material nonlinearity of matrix. The results show that significantly lower stress concentrations exist in the case of flax fibers compared to glass fiber composites, explaining the absence of transverse cracks until failure in previously conducted transverse tension tests. Increase in the applied transverse strain causes a further decrease in the stress concentrations due to the nonlinear behavior of the matrix.

Measuring Interface Strength in Single Fiber Composites: The Effect of Stress Concentrations

2000 ◽  
Vol 629 ◽  
Author(s):  
G. A. Holmes ◽  
R. C. Peterson
Keyword(s):  
Fragment Length ◽  
Interface Strength ◽  
Matrix Interface ◽  
Stress Concentrations ◽  
New Model ◽  
Testing Rate ◽  
Mechanics Model ◽  
The Matrix ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

ABSTRACTFiber-matrix interface strength is known to be a critical factor in controlling the long-term performance of structural composites. This parameter is often obtained by using the average fragment length data generated from the single-fiber fragmentation test (SFFT). The interfacial shear strength is then determined by using this data in a micro-mechanics model that describes the shear-stress transfer process between the matrix and the fiber. Recently, a non-linear viscoelastic micro-mechanics model was developed to more accurately account for the matrix material properties. This new model indicates that the interface strength is dependent on the testing rate. Experimentally, it has been shown that the final fragment length distribution in some systems is dependent on the testing rate. However, data analysis using the new model indicates that the distribution change with testing rate is promoted by the presence of high stress concentrations at the end of the fiber fragments. From the model, these stress concentrations were found to exist at very low strain values. Experimentally, the fragment distributions obtained from specimens tested by different testing rates were found to be significantly different at strain values well below the strain values required to complete the test. These results are consistent with the research of Jahankhani and Galiotis and finite element calculations performed by Carrara and McGarry. These authors concluded that stress concentrations can promote failure of the fiber-matrix interface on the molecular level. Our results support this conclusion. In addition, our research results suggest that altering the SFFT testing rate can lower the magnitude of these stress concentrations and minimize failure of the fiber-matrix interface.

scholarly journals The fiber‐matrix interface in Ioncell cellulose fiber composites and its implications for the mechanical performance

2020 ◽  
pp. 50306
Author(s):  
Mindaugas Bulota ◽  
Simona Sriubaite ◽  
Anne Michud ◽  
Kaarlo Nieminen ◽  
Mark Hughes ◽  
...  
Keyword(s):  
Mechanical Performance ◽  
Cellulose Fiber ◽  
Fiber Composites ◽  
Matrix Interface ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

Transverse Stiffness Prediction of Fibrous Metal Matrix Composites

2014 ◽  
Vol 565 ◽  
pp. 14-19
Author(s):  
Gergis W. William ◽  
Samir N. Shoukry ◽  
Jacky C. Prucz
Keyword(s):  
The Other ◽  
Matrix Composites ◽  
Matrix Interface ◽  
Transverse Loading ◽  
Cooling Process ◽  
The Matrix ◽  
Fiber Matrix Interface ◽  
Fiber Matrix ◽  
Fibrous Metal ◽  
Packing System

This paper presents two new 3D finite element Multi Fiber Models (MFM) that account for the effects of neighboring fibers on the stress distribution over fiber-matrix interface. One model assumes a hexagonal packing pattern of the neighboring fibers whereas the other assumes that the neighboring fibers are packed in a square pattern. Two scenarios regarding the contact surface between the fiber and the matrix are considered: the first one assumes no bond over the interface while in the other one the interface is perfectly bonded. The cooling process of the composite was simulated and then a transverse loading is applied to the composite. The results indicate that packing system and the characteristics of the fiber-matrix interface greatly influence the magnitude of the residual stresses developed in the matrix.

A Micromechanical Model for the Fiber Bridging of Macro-Cracks in Composite Plates

1996 ◽  
Vol 63 (1) ◽  
pp. 225-233 ◽  
Author(s):  
G. A. Kardomateas ◽  
R. L. Carlson
Keyword(s):  
Glass Fibers ◽  
Micromechanical Model ◽  
Experimental Studies ◽  
Composite Plates ◽  
Matrix Interface ◽  
Transverse Cracks ◽  
Crack Face ◽  
Fiber Bridging ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

Recent experimental studies on the propagation of transverse cracks in composites have shown that fiber bridging is frequently present, and can be considered as the cause of increased toughness. This paper presents a model that is capable of quantifying this effect and explaining the decrease in the crack growth rate in either a monotonic or a cyclic load profile. Both Modes I and II are considered. The model is based on the elastic loading of a fiber located on the macro-crack face close to the tip and under dominantly plane strain conditions. Two fundamental cases of fiber bridging configurations are distinguished, namely when the fiber-matrix interface is intact and when the fiber-matrix interface has partially failed. Following the single fiber analysis, the model is extended to the case of multiple fibers bridging the faces of the macro-crack. The analysis is for a generally anisotropic material and the fiber lines are at arbitrary angles. Results are presented for the case of an orthotropic material with unidirectional fibers perpendicular to the crack faces. Specifically, the reduction in the stress intensity factor (relative to the nominal value) is investigated for the glass fibers in a glass/epoxy composite system. The effects of fiber debonding and pullout with friction as well as fiber breaking are accounted for in the analysis, and results with respect to a parameter representing the fiber-matrix interface friction are presented. Results are also presented regarding the partial or full fracture of the fiber bridging zone. The model can also be used to analyze the phenomenon of fiber nesting, which is similar to fiber bridging, and occurs with growing delaminations.

Thermal Stresses and Thermal Expansion Coefficients of Short Fiber Composites With Sliding Interfaces

1988 ◽  
Vol 110 (2) ◽  
pp. 96-100 ◽  
Author(s):  
I. Jasiuk ◽  
T. Mura ◽  
E. Tsuchida
Keyword(s):  
Thermal Expansion ◽  
Thermal Stresses ◽  
Matrix Interface ◽  
Stress Concentrations ◽  
Displacement Potential ◽  
Thermal Expansion Coefficients ◽  
Finite Concentration ◽  
Fiber Matrix Interface ◽  
Expansion Coefficients ◽  
Fiber Matrix

The paper analyzes thermal stresses and effective thermal expansion coefficients of the composites in which the fiber-matrix interface is allowed to slip. Thermal stresses are evaluated by introducing an eigenstrain in the fibers, which corresponds to the strain due to the mismatch of thermal expansion coefficients. For simplicity, the effect of friction is neglected. Boussinesq-Papkovich displacement potential method is used in the analysis. Then, the results for a single sliding fiber are used to predict the average thermal expansion coefficients of the composite containing finite concentration of fibers. It is observed that sliding at the fiber-matrix interface causes higher stress concentrations and affects significantly the average coefficients of thermal expansion of the composite.

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