New developments for the calculation of fibre reinforced plastic laminates – nonlinear material properties and gradual failure.

E. Schmachtenberg, E. Kuhnel

Institute of Plastics Processing (IKV) at RWTH Aachen University

Pontstraße 49, 52062 Aachen, Germany

Abstract

The strength criterion for fibre reinforced plastics developed by Puck incorporates not only a thoroughly developed theory to predict the appearance of inter fibre failure, but also the necessary principles to consider the effects of appeared inter fibre failure into the calculation of laminates which are loaded further than to the point of first appearing inter fibre failure. By extensive experimental work the necessary degradation functions could now be determined experimentally. The conducted experiments are briefly described and the resulting degradation functions are given. With these degradation functions a computer program was developed, based on the classical laminate theory, to incorporate the concept of degraded plies into the calculation of laminates.

The achievable results with this program demonstrate, using the example of a ± 54,75° tube loaded with inner pressure, how close to reality the prediction of laminate deformation and of the gradual failure process in laminates has come by including the now determined degradation functions into the calculation process.