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.

scholarly journals Multiscale Characterization of Nanoengineered Fiber-Reinforced Composites: Effect of Carbon Nanotubes on the Out-of-Plane Mechanical Behavior

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Carlos Medina ◽  
Eduardo Fernandez ◽  
Alexis Salas ◽  
Fernando Naya ◽  
Jon Molina-Aldereguía ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Fracture Toughness ◽  
Shear Strength ◽  
Mechanical Behavior ◽  
Matrix Interface ◽  
Short Beam ◽  
The Matrix ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

The mechanical properties of the matrix and the fiber/matrix interface have a relevant influence over the mechanical properties of a composite. In this work, a glass fiber-reinforced composite is manufactured using a carbon nanotubes (CNTs) doped epoxy matrix. The influence of the CNTs on the material mechanical behavior is evaluated on the resin, on the fiber/matrix interface, and on the composite. On resin, the incorporation of CNTs increased the hardness by 6% and decreased the fracture toughness by 17%. On the fiber/matrix interface, the interfacial shear strength (IFSS) increased by 22% for the nanoengineered composite (nFRC). The influence of the CNTs on the composite behavior was evaluated by through-thickness compression, short beam flexural, and intraply fracture tests. The compressive strength increased by 6% for the nFRC, attributed to the rise of the matrix hardness and the fiber/matrix IFSS. In contrast, the interlaminar shear strength (ILSS) obtained from the short beam tests was reduced by 8% for the nFRC; this is attributed to the detriment of the matrix fracture toughness. The intraply fracture test showed no significant influence of the CNTs on the fracture energy; however, the failure mode changed from brittle to ductile in the presence of the CNTs.

Mechanical Property Study of the Fiber-Matrix Interface in SiC/SiC Composites

2006 ◽  
Author(s):  
Eric L. Jones ◽  
Sergey Yarmolenko ◽  
Devdas Pai ◽  
Jag Sankar
Keyword(s):  
Shear Strength ◽  
Interfacial Shear Strength ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Interfacial Shear ◽  
Fatigue Properties ◽  
Matrix Interface ◽  
Fiber Matrix Interface ◽  
Fiber Matrix ◽  
Sic Composites

The fiber-matrix interface between ceramic fibers and ceramic matrix plays a major role in the fatigue properties and toughness of continuous fiber reinforced ceramic matrix composites (CMCs). Boron Nitride (BN) is a widely used fiber coating material that provides a weak bond between the fiber and matrix. A weak fiber-matrix interface increases the strength and toughness of the overall CMC. Single fiber push-out tests were performed to study interfacial shear strength as a main parameter defining fatigue properties and toughness of SiC/SiC composites. The fiber-matrix interfacial shear strength was studied in melt infiltrated Hi-Nicalon/BN(CVI)/SiC composites exposed to various temperature and loading conditions, similar to those that are used in actual applications. Hi-Nicalon fibers with diameters of 13-14.5 μm were pushed out from samples with thicknesses ranging from 125-280 μm using a spherical tip with a 1 μm radius and 90° conical shape. Interfacial shear strength was calculated from sliding load, fiber diameter and sample thickness. Due to significant scattering, 30 individual push tests in every sample were used to obtain the average interfacial shear strength. The virgin sample has a shear strength of 20 MPa which is higher than tensile tested samples (12 MPa). Annealing of a virgin specimen for 100 hours at 1000°C slightly increased shear strength up to 21.5 MPa while annealing at 1100°C and 1200°C led to significant increase of shear strength up to 29 and 39 MPa correspondingly. This effect is associated with BN degradation at temperatures >1000°C.

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.

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).

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