Research article

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We report on unique enhancement of fracture resistance of poly(methyl methacrylate) (PMMA) using short and low bending modulus poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers. While no significant effect of the PBO fibers on stiffness and strength was observed, the strain at break and fracture energy were enhanced substantially. The in situ observations of damage development during the tensile tests showed that the additional extrinsic toughening mechanisms consists of homogenous distribution of micro-cracking and delocalization of the deformation sites to the whole volume of the sample with micro-cracks bridged by the entangled PBO fiber mesh. Employing unique toughening mechanisms of PBO fiber network in hybrid PMMA/CF/PBO composites containing both carbon (CF) and PBO fibers lead to simultaneous enhancement of stiffness, strength and toughness suitable for wide range of engineering applications.