Increasing damage tolerance in composites using hierarchical brick-and-mortar microstructures

Abstract

Composites are attractive materials because of their high specific stiffness and specific strength, but their application in industry is restricted by their inherent lack of damage tolerance and stable energy dissipation mechanisms, due to the brittleness of the fibres. Nature overcomes a similar issue by arranging natural composites, made of mostly brittle constituents, in discontinuous and hierarchical microstructures. This work aims at evaluating the potential of hierarchical discontinuous carbon-fibre reinforced polymers to achieve damage tolerance, by a combination of modelling and experiments. Two different models (one analytical and the other numerical) are developed to predict the tensile response of hierarchical brick-and-mortar microstructures with two levels of hierarchies, and to design specimens with a non-linear response. Such specimens are then manufactured using laser micro-milled carbon/epoxy thin-plies, and tested under tension. The results show that the presence of discontinuities and hierarchies promotes stable energy dissipation before failure, ensures damage diffusion throughout the specimen, and delays damage localisation in otherwise brittle composites.

Microstructure and Size Effects on the Mechanics of Two Dimensional, High Aspect Ratio Nanoparticle Assemblies

“…The multiple hierarchical levels found in many biological composites further improve their mechanical responses and failure properties Wei et al, 2015;Gao et al, 2016;Henry and Pimenta, 2018). It has been shown that hierarchal microstructures provide improved resiliency to stress concentrations near inclusions (Gorbatikh et al, 2010) and enhanced damage dispersion (Ritchie, 2011;Dutta and Tekalur, 2014;Mirzaeifar et al, 2015;Henry and Pimenta, 2018). These observations are part of a large and ever growing body of work establishing that staggered microstructures tend to be the most favorable architectures for simultaneously producing stiffness, strength, and toughness in thin, macroscopic materials (Espinosa et al, 2009;Zhang Z. Q. et al, 2010;Barthelat and Zhu, 2011;Dutta et al, 2013;Barthelat, 2014;Ni et al, 2015;Pro et al, 2015;Qwamizadeh et al, 2015Qwamizadeh et al, , 2017aAbid et al, 2018).…”

“…While significantly contributing to small strain behaviors, these interfaces also provide robust toughening mechanisms through stable energy dissipation (Mayer, 2005;Barthelat et al, 2012). The multiple hierarchical levels found in many biological composites further improve their mechanical responses and failure properties Wei et al, 2015;Gao et al, 2016;Henry and Pimenta, 2018). It has been shown that hierarchal microstructures provide improved resiliency to stress concentrations near inclusions (Gorbatikh et al, 2010) and enhanced damage dispersion (Ritchie, 2011;Dutta and Tekalur, 2014;Mirzaeifar et al, 2015;Henry and Pimenta, 2018).…”

“…The outstanding mechanical properties of natural uniaxial nanocomposites have inspired the use of staggered architectures in engineered materials. These materials have been fabricated using techniques like freeze casting (Munch et al, 2008), coextrusion (Wilkerson et al, 2018), rapid prototyping (Gu et al, 2016), and laser cutting (Henry and Pimenta, 2018). While these synthetic materials have shown impressive combinations of stiffness, strength, and toughness (Podsiadlo et al, 2007;Bonderer et al, 2008;Wang et al, 2012;de Obaldia et al, 2015;Valashani and Barthelat, 2015;Zhang et al, 2015;Gu et al, 2017;Kim et al, 2018), attempts at reconstructing the mechanical properties of natural materials often fall short of theoretical predictions (Espinosa et al, 2009;Wei et al, 2012).…”

“…This deficiency has spurred myriad studies hoping to inform the design of optimal nanocomposites built from ordered, uniaxial members embedded in relatively compliant matrices. While there have been many efforts to investigate the mechanics of these brick and mortar systems in two dimensions, they often rely on continuum (Arzt et al, 2003;Ji and Gao, 2004;Zhang Z. Q. et al, 2010;Dutta et al, 2013;Barthelat, 2014;Sakhavand and Shahsavari, 2015;Zhang et al, 2015;Ghazlan et al, 2018;Henry and Pimenta, 2018) or micromechanical (Begley et al, 2012;Abid et al, 2018;Chandler and Cheng, 2018) descriptions. Despite these constitutive and microstructural simplifications, these theoretical works have helped to elucidate many important deformation mechanisms in staggered composites.…”

Computational Homogenization of Architectured Materials

“…with different objectives. For instance, developing architectured porous materials for structural, acoustic and insulation properties [40,70], entangled monofilament of pearlitic steel [47,173], sandwich composite structures [118,[163][164][165], segmented interlocking structures [59,60,62,65,66,72,117,123,136,[145][146][147]189], asymmetric frictional materials [18,19], woven and non-woven textile composites [57,130,141], porous metallic glasses [187], hierarchical composites [92], crumpled metallic foils [34]. Much more examples can be found in the present book.…”