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.

Thermomechanical Stability of Interphases in Glass Reinforced Composites

1989 ◽  
Vol 170 ◽  
Author(s):  
A. T. Dibenedetto ◽  
Jaime A. Gomez ◽  
C. Schilling ◽  
F. Osterholtz ◽  
G. Haddad
Keyword(s):  
Thermal Stability ◽  
Shear Strength ◽  
Glass Fibers ◽  
Boiling Water ◽  
Reinforced Composites ◽  
Matrix Interface ◽  
Force Transmission ◽  
Silane Coating ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

AbstractThe thermomechanical stability of organosilane surface treatments for E-glass fibers used in fiber reinforced composites was evaluated. The effect of molecular structure of 40 to 80 namometer coatings on the force transmission across the fiber/matrix interface was measured as a function of temperature and exposure to water using a fiber fragmentation test. It was found that phenyl-substituted amino silanes exhibited better thermal stability, but were less resistant to boiling water, than the commierically available γ-amino propyl silanes. A bis-trimethoxy γ-amino propyl silane showed an increase in both the hydrolytic and thermal stability when compared to the commiercial product. A good balance of thermal and hydrolytic stability was also obtained with a methylaminopropyltrimethoxy silane coating.The strain energy released from the glass fibers upon decoupling from the poxy matrix or silane coating was found to be in the range of 145 to 186 g/m2 and varied no more than 20 percent over a temperature range of 25 to 75°C or when exposed to boiling water and then redried. It also varied very little with the silane coating used. In addition, the average shear stress attained at the fiber-matrix interface in an imbedded single fiber test at 25°C was as much as two times higher than the shear strength of the epoxy matrix and as much as five times higher at elevated temperature. These data lead one to the conclusion that the interphase failure in these composites is controlled by a plane strain fracture in the constrained region of the organic phase, near the fiber surface, rather than by the maximum shear strength in the interphase.

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.

scholarly journals Sensitivity Analysis of Fiber-Matrix Interface Parameters in an SMC Composite Damage Model

Proceedings ◽  
2018 ◽  
Vol 2 (8) ◽  
pp. 544 ◽  
Author(s):  
Johannes Görthofer ◽  
Malte Schemmann ◽  
Thomas Seelig ◽  
Andrew Hrymak ◽  
Thomas Böhlke
Keyword(s):  
Glass Fibers ◽  
Damage Model ◽  
Interface Strength ◽  
Strength Distribution ◽  
Interface Debonding ◽  
Matrix Interface ◽  
Molding Compound ◽  
Fiber Matrix Interface ◽  
Fiber Matrix ◽  
Interface Parameters

This contribution shortly introduces the anisotropic, micromechanical damage model for sheet molding compound (SMC) composites presented in the authors’ previous publication [1]. As the considered material is a thermoset matrix reinforced with long (≈25 mm) glass fibers, the leading damage mechanisms are matrix micro-cracking and fiber-matrix interface debonding. Those mechanisms are modeled on the microscale and within a Mori-Tanaka homogenization framework. The model can account for arbitrary fiber orientation distributions. Matrix damage is considered as an isotropic stiffness degradation. Interface debonding is modeled via a Weibull interface strength distribution and the inhomogeneous stress distribution on the lateral fiber surface. Hereby, three independent parameters are introduced, that describe the interface strength and damage behavior, respectively. Due to the high non-linearity of the model, the influence of these parameters is not entirely clear. Therefore, the focus of this contribution lies on the variation and discussion of the above mentioned interface parameters.

scholarly journals Effects of PTFE Micro-Particles on the Fiber-Matrix Interface of Polyoxymethylene/Glass Fiber/Polytetrafluoroethylene Composites

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2164 ◽  
Author(s):  
Jasbir Singh ◽  
Yern Ching ◽  
De Liu ◽  
Kuan Ching ◽  
Shaifulazuar Razali ◽  
...  
Keyword(s):  
Wear Resistance ◽  
Friction And Wear ◽  
Glass Fibers ◽  
Weight Ratio ◽  
Tribological Performance ◽  
Transfer Film ◽  
Matrix Interface ◽  
Micro Particles ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

Reinforcing polyoxymethylene (POM) with glass fibers (GF) enhances its mechanical properties, but at the expense of tribological performance. Formation of a transfer film to facilitate tribo-contact is compromised due to the abrasiveness of GF. As a solid lubricant, for example, polytetrafluoroethylene (PTFE) significantly improves friction and wear resistance. The effects of chemically etched PTFE micro-particles on the fiber-matrix interface of POM/GF/PTFE composites have not been systematically characterized. The aim of this study is to investigate their tribological performance as a function of micro-PTFE blended by weight percentage. Samples were prepared by different compositions of PTFE (0, 1.7, 4.0, 9.5, 15.0 and 17.3 wt.%). The surface energy of PTFE micro-particles was increased by etching for 10 min using sodium naphthalene salt in tetrahydrofuran. Tribological performance was characterized through simultaneous acquisition of the coefficient of friction and wear loss on a reciprocating test rig in accordance to Procedure A of ASTM G133-95. Friction and wear resistance improved as the micro-PTFE weight ratio was increased. Morphology analysis of worn surfaces showed transfer film formation, encapsulating the abrasive GF. Energy dispersive X-ray spectroscopy (EDS) revealed increasing PTFE concentration from the GF surface interface region (0.5, 1.0, 1.5, 2.0, 2.5 µm).

scholarly journals Rationalizing the impact of aging on fiber–matrix interface and stability of cement-based composites submitted to carbonation at early ages

2016 ◽  
Vol 51 (17) ◽  
pp. 7929-7943 ◽  
Author(s):  
G. H. D. Tonoli ◽  
V. D. Pizzol ◽  
G. Urrea ◽  
S. F. Santos ◽  
L. M. Mendes ◽  
...  
Keyword(s):  
Matrix Interface ◽  
Fiber Matrix Interface ◽  
Fiber Matrix ◽  
The Impact
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