Bearing behavior of additively manufactured Onyx–Kevlar composites: effect of fiber content and mixed distribution

Abstract This study investigates the pin-bearing behaviour of additively manufactured Onyx–Kevlar composites, focusing on the interplay between fiber content and layer-wise distribution. Specimens were fabricated via Continuous Filament Fabrication with longitudinal Kevlar coverage ranging from 0 to 100% and tested under bearing loading. While increasing fiber content enhances stiffness and strength, intermediate configurations (25–75%) exhibit a performance plateau due to premature failure at the interface between reinforced and unreinforced regions, preventing the development of a fully bearing-dominated response. Hybrid and iso-fiber-weight configurations reveal that stiffness and strength are primarily governed by the presence of fully reinforced layers interacting with the pin, allowing reduced-fiber laminates to match the performance of fully reinforced specimens. However, configurations with identical fiber mass but discontinuous reinforcement show reduced deformation capacity and lower specific energy absorption, indicating that failure behaviour is strongly influenced by reinforcement continuity. These results demonstrate that bearing performance in CFF composites cannot be predicted solely from total fiber content. Instead, stiffness and strength are controlled by the stiffest load-bearing layers, whereas energy absorption and damage evolution are governed by the continuity of reinforcement across the laminate. This distinction provides a design framework for optimizing fiber placement in additively manufactured composites, enabling weight reduction without compromising structural performance while avoiding premature failure.