Toughening mechanisms of fiber-reinforced composites: A micromechanical heterogeneous peridynamic model

Exploring strategies for toughening the fiber-reinforced composites (FRCs) is of significant interest for boosting their high-performance applications. A novel micromechanical peridynamic (PD) model incorporating five types of non-local interactions was proposed to unravel the toughening mechanisms for laminated composite materials. This PD model was validated by three examples including the prediction of off-axis modulus of laminates, the cracking of center-cracked laminates and the compact tension test. Diverse experiment-consistent crack patterns were captured. The effects of the mechanical properties of fibers, matrix, their interface and the interlayer interface on the force–displacement curves obtained from compact tension tests were systematically studied. It was found that the major load carrier is the fiber, follow by the fiber–matrix interface, the interlayer interface and the matrix. Results show that the stiffening and strengthening of fiber–matrix interface and interlayer interface can greatly enhance the fracture toughness of the composites. This toughening is resulted from a synergetic improvement of load bearing capacity in the interlayer bonds, fiber–matrix bonds, the fiber bonds and matrix bonds. To leverage this synergetic effect, interface and interlayer enhancement strategies, e.g., brick–mortar structure and the Bouligand structure appeared in biological materials, are highly recommended for designing FRCs with improved toughness.