Damage accumulation under mechanical loading in hybrid composite reinforced by 3D-knitted fabric and oil shale ash powder

Hybrid composite materials (HCMs) containing knitted fabric as reinforcement often improve the mechanical properties and retard failure process in the loaded structure. In the present investigation, using numerical methods, was modeled damage accumulation process in a HCM, prepared by uniformly impregnating a knitted fabric of basalt microfiber yarn with epoxy resin having dispersed fine oil shale ash (OSA) particles. The HCM plate was investigated experimentally and performing numerical modelling of damage accumulation in it. The elastic modulus of the polymer matrices at different OSA concentrations was experimentally measured. This data was then used in a finite element model to calculate stresses in the reinforced textile inside the loaded plate. Impregnated yarns in the textile were modeled as macrofibers (MFs) with averaged properties, and their geometry was described using the Leaf–Glaskin approach. Next, the damage accumulation process was simulated under an external unidirectional tensile load. Depending on the applied load, different parts of the MF loops experience overloading. At some point, one of the most overloaded MF cross-sections breaks, as described using the probabilistic Weibull function. The Weibull distribution parameters were accepted using data for single fiber rupture. This leads to increased overload on the cross-sections of adjacent MF loops and eventually their breakage as well. A stochastic numerical model of sequential MF rupture accumulation was developed to describe the probabilities of defects that consist of various numbers of adjacent broken MFs. Analytical and stochastic methods were used to determine the load-carrying capacity and the accumulation of defects of different sizes in the HCM plate.