A novel continuum-decohesive finite element for modeling in-plane fracture in fiber reinforced composites

2013 ◽  
Vol 83 ◽  
pp. 1-10 ◽  
Author(s):  
Pavana Prabhakar ◽  
Anthony M. Waas
Author(s):  
Chensong Dong

The coefficients of thermal expansion (CTEs) of fiber reinforced composites play an important role in the design and analysis of composite structures. Since the thermal expansion coefficients of polymer matrix materials are typically much higher than those of fibers, and the fiber often exhibits anisotropic thermal and mechanical properties, the stress induced in the composite due to temperature change is very complex. Large discrepancies exist among the analytical models for the transverse CTE of unidirectional composites. Hence, it is problematic when choosing a suitable model. With the development of computer technologies, finite element analysis (FEA) proved its effectiveness in calculating the effective CTE of composites. In this study, the transverse CTEs of unidirectional carbon fiber composites were calculated by finite element analysis using a representative unit cell. The analytical micromechanical models from literature were compared against the FEA data. It shows that Hashin’s concentric cylinder model is the best. However, it is inconvenient for practical applications due to the amount of computation. In this study, based on the FEA data, an engineering model for predicting the transverse CTE of unidirectional composites was developed by regression analysis. This model was validated against the FEA and experimental data. It shows that the developed model provides a simple and accurate approach to calculate the transverse CTE of unidirectional composites.


Author(s):  
M. M. Shokrieh ◽  
A. R. Ghanei Mohammadi

In this paper, a new finite element model has been introduced with the aim of efficient investigation of residual thermal stresses in fiber-reinforced composites, in which the inhomogeneous interphase is considered. For the inhomogeneous interphase modeling, four different kinds of material properties variation of the interphase (power, reciprocal, cubic and exponential variations) with the radial coordinate have been used. A mono fiber circular unit cell is considered using a finite element (FE) method. Extending the mono fiber model, FE models with different arrays of fibers have been created to investigate the effects of neighboring fibers on the results. In order to assure the convergence of results, a convergence analysis has been carried out for each of the models. To verify the finite element model, the FE results are compared with theoretical results available in the literature. In this paper, three different types of RVE configurations, circular, square and hexagonal are modeled and the effects of each type of fiber packing are studied. Performing an extensive study, the appropriate boundary conditions for RVEs are presented. The boundary conditions presented in this research are proved to be able to model the overall behavior efficiently.


The objective of this study is to investigate the fatigue behavior of sisal fiber reinforced with carbon nanotubes. The hand lay-up technique is used to prepare the composite material samples. The fatigue response of pure polymer matrix, composite material which is prepared by reinforcing a sisal fiber reinforced with a polymer matrix was studied. The effectiveness of nano reinforcement of fatigue response is identified from experiments. Later, the fatigue response of sisal and nano particle reinforced sisal fiber composites (hybrid composite) is identified with irregularities by using finite element based software ANSYS. The elastic properties of sisal fiber reinforced composite and carbon nanotube reinforced composite is estimated by using the principles of Micromechanics and Macro-mechanics. The failure mechanism of polymer, conventional sisal fiber composites and nano filled sisal fiber reinforced composites are identified. The effect of the shape of the irregularities on the fatigue response is also identified from ANSYS software. From the present work, it is observed that, the reinforcement of nano reinforcement has considerable influence on the fatigue response of the resulting composite.


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