Stress concentrations near a fiber break in unidirectional composites with interfacial slip and matrix yielding

2004 ◽  
Vol 41 (16-17) ◽  
pp. 4263-4277 ◽  
Author(s):  
N. Ohno ◽  
S. Okabe ◽  
T. Okabe
Keyword(s):  
Interfacial Slip ◽  
Stress Concentrations ◽  
Fiber Break ◽  
Unidirectional Composites ◽  
Matrix Yielding

Dynamic effects of a single fiber break in unidirectional glass fiber-reinforced polymer composites: Effects of matrix plasticity

2017 ◽  
Vol 52 (14) ◽  
pp. 1873-1886 ◽  
Author(s):  
Raja Ganesh ◽  
Subramani Sockalingam ◽  
John W Gillespie
Keyword(s):  
Yield Strength ◽  
High Speed ◽  
Dynamic Stress ◽  
Interfacial Debonding ◽  
Single Fiber ◽  
Stress Concentrations ◽  
Fiber Break ◽  
The Matrix ◽  
Matrix Yielding ◽  
Dynamic Stress Concentrations

In a unidirectional composite under static tensile loading, breaking of a fiber is shown to be a locally dynamic process, leading to stress concentrations in the matrix and neighboring fibers and debonding of the interface, which can propagate at high speed over long distances. In our previous work, a fiber break within a two-dimensional fiber array embedded in elastic epoxy matrix (with cohesive interface) was modeled to quantify the effects of these dynamic stresses. The results indicated that the elastic limit of the polymer matrix can be exceeded. In this study, the effects of matrix plasticity on dynamic stress concentrations due to a single fiber break are investigated. For the range of matrix yield stresses considered, the dynamic stress concentrations are significantly higher than corresponding values predicted by a quasi-static model with a pre-broken fiber. Based on the ratio of shear yield strength of the matrix and mode II peak traction of the interface cohesive law, two distinct regimes of damage are shown to exist. Only matrix yielding occurs when this ratio is less than 1.0, while both interfacial debonding and matrix yielding occur when it is greater than 1.0. At higher fiber break strengths, where the elastic matrix model predicts unstable interfacial debonding, reduction in matrix yield strength leads to a transition to stable debonding and arrest. Reducing the matrix yield strength also leads to a lowering of the peak dynamic stress concentrations in adjacent fibers, while spreading the stress concentrations over a larger volume of the composite microstructure.

Stresses in a composite material with a single broken fibre

1967 ◽  
Vol 2 (3) ◽  
pp. 239-245 ◽  
Author(s):  
M J Iremonger ◽  
W G Wood
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Composite Material ◽  
Composite Materials ◽  
High Stress ◽  
The Finite Element Method ◽  
Stress Concentrations ◽  
Lower Stress ◽  
Fibre Break ◽  
Matrix Yielding

An investigation has been made into the suitability of the finite-element method for studying the stresses in composite materials and the case of a single broken fibre in a matrix has been examined. It has been found that high stress concentrations occur in the region of the fibre break which increase with decreasing end gap and would cause matrix yielding or fracture at comparatively low overall stresses. When the end gap is not void but filled with matrix much lower stress concentrations occur which, below a certain value of end gap, actually decrease as the gap is made smaller.

scholarly journals Dynamic effects of single fiber break in unidirectional glass fiber-reinforced composites

2016 ◽  
Vol 51 (9) ◽  
pp. 1307-1320 ◽  
Author(s):  
Raja Ganesh ◽  
Subramani Sockalingam ◽  
Bazle Z (Gama) Haque ◽  
John W Gillespie
Keyword(s):  
High Speed ◽  
Glass Fibers ◽  
Element Model ◽  
Unidirectional Composite ◽  
Stress Concentrations ◽  
Fiber Fracture ◽  
Fiber Break ◽  
Axial Tensile ◽  
Brittle Fiber ◽  
Static Tensile

In a unidirectional composite under static tensile loading, breaking of a fiber is shown to be a locally dynamic process that leads to stress concentrations in the interface, matrix and neighboring fibers that can propagate at high speed over long distances. To gain better understanding of this event, a fiber-level finite element model of a two-dimensional array of S2-glass fibers embedded in an elastic epoxy matrix with interfacial cohesive traction law is developed. The brittle fiber fracture results in release of stored strain energy as a compressive stress wave that propagates along the length of the broken fiber at speeds approaching the axial wave-speed in the fiber (6 km/s). This wave induces an axial tensile wave with a dynamic tensile stress concentration in adjacent fibers that diminishes with distance. Moreover, dynamic interfacial failure is predicted where debonding initiates, propagates and arrests at longer distances than predicted by models that assume quasi-static fiber breakage. In the case of higher strength fibers breaks, unstable debond growth is predicted. A stability criterion to define the threshold fiber break strength is derived based on an energy balance between the release of fiber elastic energy and energy absorption associated with interfacial debonding. A contour map of peak dynamic stress concentrations is generated at various break stresses to quantify the zone-of-influence of dynamic failure. The dynamic results are shown to envelop a much larger volume of the microstructure than the quasi-static results. The implications of dynamic fiber fracture on damage evolution in the composite are discussed.

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