Issue 50

M.A. Khiat et alii, Frattura ed Integrità Strutturale, 50 (2019) 595-601; DOI: 10.3221/IGF-ESIS.50.50 595 Focused on Fracture Mechanics versus Environmen Effect of environmental conditions on the resistance of damaged composite materials Sidi Mohammed Amine Khiat, Ramdane Zenasni, Mawloud Hamdi University of Mostaganem, Algeria aminek@netcourrier.com, zramdane@netcourrier.com, mawloud.hamdi@univ-mosta.dz A BSTRACT . The present paper proposes a strength model for unidirectional composites with Lin/Epoxy. The model assumes that, a central core of broken fibers flanked by unbroken fibers which are subject to stress concentrations from the broken fibers. The approach of the model consists of using a modified shear lag model to calculate the ineffective lengths and stress concentrations around fiber breaks. In this paper, we attempt to incorporate in the proposed model the unidirectional composite property variation with temperature and moisture in order to predict even composite strength degradation. Strength degradation is often seen as a result of changes in ineffective lengths at fiber breaks. Subsequently, damage to the material can be estimated at the micromechanical scale under the effect of temperature and humidity. K EYWORDS . Unidirectional composite; Broken fibers; Micromechanics; Composite Lin/Epoxy. Citation: Khiat, M.A., Zenasni, R., Hamdi, M., Effect of Environmental Conditions on the Resistance of Damaged Composite Materials, Frattura ed Integrità Strutturale, 50 (2019) 595-601. Received: 04.03.2019 Accepted: 26.07.2019 Published: 01.10.2019 Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION arbon fibers reinforced polymers are widely applied for mechanical and structural components because of their high specific strength and rigidity, and excellent durability. Because such reinforcing fibers are generally brittle and have a large scatter in strength, mechanical properties of composites have often been discussed from the viewpoint of materials reliability engineering. Predicting the strength of these materials from the properties of their constituents is a task which has not yet been solved for all classes of materials. From literature, oldest models have been used for predicting the strength of polymer matrix composites are introduced by Zweben and Rosen [1, 2]. Both authors related the failure of the fiber bundles in the company of the matrix material. They used the ineffective length to estimate the tensile strength. This was based on shear lag analysis. However, this model did not consider the effects of stress concentrations in the fibers adjacent to the broken one. Phoenix et al. [3] obtained statistical strength and rupture lifetimes of unidirectional model carbon fiber/epoxy matrix micro-composites. Their model consists of seven parallel carbon fibers forming approximate hexagonal packing embedded in an epoxy matrix. Landis et al. [4] addressed the question of how to choose effective dimensions of the matrix springs connecting C