Abstract
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.
Highlights
Carbon fibers reinforced polymers are widely applied for mechanical and structural components because of their high specific strength and rigidity, and excellent durability
The model assumes that, a central core of broken fibers flanked by unbroken fibers which are subject to stress concentrations from the broken fibers
When a fiber breaks in the composite, there is a region of influence generated around the end of the broken fiber where a stress concentration exists
Summary
Carbon fibers reinforced polymers are widely applied for mechanical and structural components because of their high specific strength and rigidity, and excellent durability. 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. This was based on shear lag analysis 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. The problem was solved by applying standard elasticity assumptions, with appropriate choice of stress functions in each constituent This solution was applied to the problem of a fiber fracture in a unidirectional composite material by making geometrical assumptions. After the calculation of stress concentrations and ineffective lengths of composite Lin/Epoxy
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