Mechanics of Damage and Degradation in Random Short Glass Fiber Reinforced Composites

Abstract

The present study is part of an ongoing research work on damage of random short fiber reinforced composites. First, the tensile behavior of the material was studied. In its initial state, the material is planarly isotropic elastic. As the load increases, damage induces an anisotropic degradation of the material properties. Then, the degradation mechanisms were studied from microscopic observations of polished specimens. Finally, a theoretical model based on damage mechanics is proposed to predict the mechanical behavior of the material. Damage variables are used to evaluate the change of the compliance tensor. The evolution laws of the damage variables are established within a thermodynamic framework using the associated thermodynamic forces. Correlation with the tensile test results is good. However, additional experiments have to be carried out to fully validate the proposed model.

Experimental Characterization of Damage in Random Short Glass Fiber Reinforced Composites

“…Given that each strand contains about 300 fibers, the length-to-diameter ratio of a strand is 175. Microscopic observations of the composite [7] still revealed the presence of a significant number of entrapped air bubbles, and confirmed the random orientation of the fibers through the thickness. Therefore, the material was expected to initially exhibit an in-plane isotropic behavior.…”

“…As can be observed, as the applied stress increases, elastic modulus progressively decreases while the permanent strains increase. From the elastic modulus, variable D 1 could be evaluated using Equation (7). Poisson's ratios are also indicated in Table 1.…”

“…Their development undergoes different stages. First, cracks initiate at fiber ends and around air bubbles entrapped in the material [7]. As the stress is further increased, the microcracks grow in the material.…”

Investigation of mechanical impact behavior of short carbon-fiber-reinforced PEEK composites

“…4), consistent with other studies [7,8], have demonstrated that fiber alignment affects the mechanical properties of SCFR-PEEK. Model parameters were 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 9 identified based on the experimental results of compressive tests, using the methodology reported for PEEK polymers [21] and assuming brittle linear elastic behavior in compression [34][35][36].…”

An incremental 2D constitutive model accounting for linear viscoelasticity and damage development in short fibre composites

“…Equation (47) must be obtained experimentally and in previous work [7,11] it has been shown that, using uniaxial tensile loading data, an initially isotropic short fibre composite can be described with a linear relationship:…”