Carbon-Epoxy Composite Fatigue Strength – Experiment and Fem Numerical Estimation

Abstract

The development of composite materials characterized by the constant amelioration of their mechanical properties (stiffness and strength) has widened their application for structural elements, mainly in aeronautical, naval and automobile industries. The possibility of tailoring the composite's properties appropriately to the applied load (by changing the direction of the fibre alignment and applying a corresponding matrix) results in the growing importance of the design process. The paper presents a numerical technique of determining the fatigue strength of the laminated carbon-epoxy composite. The experimental investigations were carried out to determine the complete set of the stiffness characteristics E ij , G ij , ij , the strength characteristics i,n , i,n. and the S-N fatigue curves. The static and fatigue numerical calculations were carried out for the material anisotropic model of the particular composite layers. Eight-node 3D finite elements with the composite's properties were used to develop the specimen's numerical model. The contact problem between the composite layers enabling the reflection of a mutual interaction was taken into account. The numerical investigation also included the state of effort analysis and the fatigue life assessment of the composite. The assessment of the composite's fatigue life was performed using the MSC.Fatigue code. The verification of models and numerical analysis was carried out for composite specimens made of the CE 8201-245-45/120 prepreg. The experimental verification confirmed that the places of the lowest fatigue life, found out in numerical analysis, are located in the area of the gauge part.

Implant and submodeling techniques for detailed finite element study of inserts in composites

“…The following are the material properties used for the matrix (Derived from tests as per ASTM) used for the calculations [8].…”