Finite-element modeling of initial matrix failure in CFRP under static transverse tensile load

The failure of transversely loaded unidirectional CFRP has been investigate d by the use of mechanical and thermo-mechanical test methods and finite-el ement analysis. The case considered here is characterized by a high interfa cial strength between fiber and matrix, so that matrix failure governs the fracture process of the composite. On the basis of the experimental results , the parabolic and other failure criteria were applied to the FE calculati ons. The failure dependence of the resin on the actual stress state could b e described. Furthermore, the influence of thermal residual stresses on the initial matrix failure has been investigated, and the actual stiffnesses a nd thermal expansion changes of the epoxy resins and the composites as a fu nction of temperature have been determined experimentally. The results of t he mechanical and thermo-mechanical tests performed on the pure resins and on the composites were incorporated into a finite-element analysis and comp ared with the transverse tensile properties of the composite laminates. In the FE analysis, the local fiber-volume fraction was varied over a wide ran ge in order to investigate its influence on the thermal residual stresses a nd transverse composite strength. The results could explain the low strain to failure of transverse laminates under tensile loading. (C) 2000 Elsevier Science Ltd. All rights reserved.