Tough Cortical Bone-Inspired Tubular Architected Cement-based Material

TL;DR

This paper introduces a bioinspired tubular cement-based material with a novel stepwise cracking mechanism, significantly improving fracture toughness through engineered microstructures, inspired by cortical bone's osteons and cement lines.

Contribution

It develops a hybrid 3D-printing/casting method to create architected tubular cement materials with enhanced toughness and introduces disorder curves for microstructural characterization.

Findings

Fracture toughness increased up to 5.6 times compared to monolithic cement.

Engineered tube size and shape influence crack deflection and toughness.

Disorder curves effectively quantify architected material arrangements.

Abstract

Cortical bone is a tough biological material composed of tube-like osteons embedded in the organic matrix surrounded by weak interfaces known as cement lines. The cement lines provide a microstructurally preferable crack path, hence triggering in-plane crack deflection around osteons due to cement line-crack interaction. Here, inspired by this toughening mechanism and facilitated by a hybrid (3D-printing/casting) process, we engineer architected tubular cement-based materials with a new stepwise cracking toughening mechanism, that enabled a non-brittle fracture. Using experimental and theoretical approaches, we demonstrate the underlying competition between tube size and shape on the stress intensity factor from which engineering stepwise cracking can emerge. Two competing mechanisms, both positively and negatively affected by the growing tube size, arise to significantly enhance the overall fracture toughness by up to 5.6-fold compared to the monolithic brittle counterpart without sacrificing the specific strength. This is enabled by crack-tube interaction and engineering the tube size and shape, which leads to stepwise cracking and promotes rising R-curves. Disorder curves are proposed for the first time to quantitatively characterize the degree of disorder for describing the representation of architected arrangement of materials (using statistical mechanics parameters) in lieu of otherwise inadequate periodicity classification.