Material characterisation and failure envelope evaluation of filament wound GFRP and CFRP composite tubes

Abstract

The full procedure for material characterisation of filament wound composite pipe is reported. Two different typologies of composite were used in order to evaluate the performance of the developed test methodology. Test samples were produced with glass/vinylester and carbon/epoxy in tubular section by filament winding. Split disk and biaxial tests were used to evaluate the basic in plane material properties. A new design for the biaxial test was developed. The end tabs and fixture were made in order to reduce the stress concentration at the edges of the samples and to remove any possibility of sample misalignment. The influence of the sample length as well as the sample preparation was investigated and the best solution reported. Moreover, an innovative optical method was developed for the evaluation of the void content of the produced material. In addition to the basic strength data, the complete failure envelopes in the plane s2 t12 were also evaluated for both materials by the use of the biaxial test procedure here developed. The experimental failure envelopes were also compared with the prediction made with some of the most common failure theories currently available. The results clearly showed the ability of the Puck criterion to accurately predict the failure envelope (especially when torsion plus axial compressive loads were applied to the samples).