David Mellier

Full-Field Measurement at the Weave Scale in Hemp/Epoxy Composite Using Digital Image Correlation

This paper presents the strain field analysis of a woven hemp composite. Two different stacking sequences were tested: [0/90]7 and [±45]7. Tensile tests were coupled with a digital image correlation method in order to measure in-plane longitudinal, transverse and shear strain fields. Strong heterogeneities were observed in both stacking sequences. The obtained spatial resolution was fine enough to allow the comparison of maximum and minimum deformation areas in strain fields with the corresponding weave architecture. It was observed that strain levels were directly linked with strand positions. Results gave, for the studied woven hemp composite, a complete analysis of the local deformation mechanisms.

Numerical Determination and Experimental Validation of a Technological Specimen Representative of High-Pressure Hydrogen Storage Vessels

A technological specimen representative of type IV high-pressure hydrogen storage vessels is developed. An analytical model is used to compute fiber orientations in the specimen in order to be as representative as possible of the stress level reached in a tank during pressurization. A three-dimensional finite-element model is used to determine the best stacking sequence with these fiber orientations. A validation is done by performing tests with digital image correlation in order to measure displacements on the lateral side of the specimen. A comparison between the calculated and experimentally found strain fields is made. The results obtained highlight the influence of stacking sequence on the development of damage and the difficulty arising in designing representative specimens.