Evaluating the Mechanical Properties of 3D Woven Carbon-Epoxy Composite Materials Using Experimental Data and FEA Methods

Abstract

A series of tensile, compression and shear tests were carried out on carbon-epoxy composite materials to evaluate their mechanical properties. The experiments were set upin accordance with ASTM standards that best corresponded to the test specifications. Specimens were categorized into groups according to their dimensions and shape. Based on testing requirements, some were cut into rectangular and others into dog bone specimens to determine the effects of stress concentration. A number of specimens were reinforced at both ends by means of tabs which were bonded on both faces to reduce the effects of the external pressure exerted on them through the grips of the testing machines, and the rest of them were tested without any reinforcement tabs. All the specimens were tested until failure. Load, elongation (displacement) and strain data were recorded by means of strain gages and data acquisition systems. The experimental results obtained from similar tests on different groups are compared to examine the conformity of the results regardless of dimension and geometry, and are also verified by Finite Element Analysis (FEA). In addition, FEA is used to study different conditions, such as geometry, that could affect the final results. The experimental data are analyzed and effects of fiber direction on failure method are studied. It was concluded that shape and geometry factors as well as fiber direction influenced the failure method. The work, however, is still in progress and tests under conditions, such as elevated temperature, will be conducted to study other effects on the mechanical properties of 3D woven carbon-epoxy composites.