Observation of the structure of a composite polypropylene/flax and damage mechanisms under stress

The knowledge of the microstructure and of the damage mechanism under mechanical solicitation of polypropylene (PP)/flax fiber composites is a key point of their development. The aim of this work is to study the fibers orientation and dispersion as well as the damage development of an injected PP/flax fiber composite. First, we studied the flax fiber orientation in the skin and core layers, and, to quantify the impact of fiber bundles, we evidenced their presence in injected specimens, and we focused on their effects on the tensile properties. Then, we correlated this morphology with the tensile properties of the various areas. Finally, we investigated the initiation and propagation of cracks into the PP/flax composite in tensile mode by using in situ SEM observations. Despite some differences, our results highlighted many similarities between the flax fiber and glass fiber composites, and evidenced some improvements to carry out in order to increase the part of industrial PP/vegetal fibers composites.

► We evaluate the microstructure and the damage mechanisms of injected PP/flax composites.
► Important skin/core effect.
► Influence of the microstructure on mechanical properties.
► Influence of flax fiber bundles on the mechanical behavior.
► Damage mechanisms correlated with those of glass fiber composites.