Modeling and Testing the Fracture Process of Impregnated Carbon-fiber Roving Specimens During Bending: Part I – Fiber Bundle Model

Abstract

A summarizing description of a statistical modeling method partly based on earlier publications is given to predict the total loading and breaking process of fiber bundles generated by tensile tests. This method uses some types of idealized fiber bundles, the so-called fiber bundle cells (basic types: E, EH, ES, and ET) to model the structure of real fibrous structures. Using one of these bundle cells or a composite bundle made of some bundle cells connected in parallel, the expected value and standard deviation of the whole damage process of this bundle can be calculated up to the breakage of the last intact fiber during a mechanical test. As a new application the fracture process of unidirectional composite beam is modeled during the 3P bending test considering the beam is built up of elementary embeddedfiber layers considered as E-type fiber bundle cells in the first step. Formulae for calculating the expected value and standard deviation processes of the bent specimen are elaborated assuming that the fiber breakages determined the failure of layers.

Modelling tensile force oscillation during the tensile test of PET specimens

“…Model parameters, such as E 0 , E 1 , η 0 , η 1 , ε c and ε f 0 can be calculated from Equation (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). If σ 0 is known E 0 can be determined from Equation (8) and solving the Equation (18) τ 0 can be obtained: (18) and from Equation (6) η 0 can be calculated. Equation (19) is given by Equation (16) for the (i+1)-th time interval at t i+1 :…”

“…It means that the molecular chains in the amorphous phase assemble into micro-bundles in front of the deformation zones forming voids, some of which may develop into macro-cavities. Amorphous chains can be considered as part of an EH type fibre bundle [17,18] consisting of crimped fibres which are perfectly flexible and do not transmit tensile force while being crimped (Figure 4). It is assumed that the EH bundle cell is enclosed into a rigid box which remains intact until exposed to a critical force level.…”

“…Fibres belonging to the same class form a partial bundle, a so-called fibre bundle cell. In this article a pre-stressed, breaking fibre bundle (so-called EH bundle) is used [17,18], with independent fibres, the strings defined by the clamping points are well ordered, but the individual fibres may be either pre-stressed with a statistically variable ε 0 elongation (ε 0 > 0), or may be loose, i.e. crimped (-1 < ε 0 < 0).…”

Development and Analysis of New Filament Wound Composite Pipes Made of Glass Fiber Reinforced 3P Resin

“…The 9% deformation tests were passed by each pipe except for 4PI and 6PI and the 15% deformation tests were failed by each pipe except for 1PI, 3PI, 5PI, 10PI, 11PI, 15PI and 16PI. The failure type of the composite ring specimens was typically delamination [15,16] (Fig. 12).…”

Investigation of fiber/matrix adhesion: test speed and specimen shape effects in the cylinder test

“…3). This can be modeled by the deformation and failure behavior of a yarn consisting of fibers of strong waviness [20]. To prove this hypothesis the fiber surface was coated by silicone oil to prevent the formation of active tie molecules at the fiber/matrix interphase.…”