A computational micromechanics investigation of longitudinal strength in unidirectional fibre reinforced composites

The use of Fibre Reinforced Polymers (FRP) composites has grown in popularity over the last few decades. They offer outstanding mechanical properties combined with a low density, making them an excellent solution for many lightweight applications. However, their low fracture toughness translates into brittle behaviour that often leads to catastrophic failure without prior damage symptoms. Moreover, there is a lack of reliable tools for the design of FRP with mitigated brittleness because of the complexity of the micromechanisms involved and the difficulties of experimental validation. These two factors constitute a serious drawback that limits the application of FRP to a wider engineering space. As a result, virtual testing of composite materials emerges as a promising strategy for reducing experimental programs devoted to the characterization of these materials. Nonetheless, because FRP failure is controlled by microscale phenomena, there is a need for a multiscale scheme that captures them using micromechanical models. In this thesis, the capability of computational micromechanics to make virtual predictions of failure processes in unidirectional FRP composites is extended with respect to the state of the art. Towards this end, several computational micromechanics methods are developed, each with its own challenge and research objective ; L'ús de materials compostos de polímers reforçats amb fibra (FRP) ha guanyat popularitat en les darreres dècades. Ofereixen excel·lents propietats mecàniques combinades amb una baixa densitat, cosa que els converteix en una excel·lent solució per a moltes aplicacions de pes lleuger. Tot i això, la seva baixa tenacitat a la fractura es tradueix en un comportament fràgil que sovint condueix a falles catastròfiques sense símptomes previs de dany. A més, hi ha una manca d'eines fiables per al disseny de FRP amb fragilitat mitigada a causa de la complexitat dels micromecanismes involucrats i les dificultats de validació experimental. Aquests dos factors constitueixen un ...