Fatigue performance and failure mechanisms of pultruded GF/PP rivets in single lap composite joints

• GF/PP rivets give the highest specific strength: 2,706 N/g vs 772 N/g (bolted), with up to ∼65% weight saving. • Hybrid joints show staged load sharing with Fmax 4,089 N, exceeding adhesive (2,786 N) and rivet (2,976 N) alone. • Riveted fatigue is fiber-dominated; k = 0.041, lower than hybrid (0.075) and adhesive (0.085). • Non-invasive failures (head debonding, shank shear) preserve laminate; bolts cause laminate shear-out. The design of lightweight composite structures is often limited by the performance and weight of joining methods, yet their long-term fatigue behavior remains largely unexplored. This study experimentally investigates the static and fatigue behavior of composite joints fastened with pultruded glass fiber/polypropylene (GF/PP) rivets, comparing their performance to bolted, adhesively bonded, and hybrid joints under tension–tension loading. While riveted joints showed lower absolute strength than bolted and hybrid joints, they offered the highest specific joint strength, nearly three times that of their bolted counterparts. This presents a clear design advantage for mass-sensitive applications. In fatigue, the riveted joints exhibited superior relative performance, reflected in a significantly flatter normalized F-N curve slope and thus a lower damage rate compared to the adhesive and hybrid joints. The hybrid configuration demonstrated a synergistic effect in static strength; however, its fatigue performance was dominated by the adhesive’s high damage rate. Riveted joints reached an endurance limit of one million cycles at 50% of their ultimate load. Typical failure modes were rivet head debonding or rivet body shear. Crucially, this behavior enables a fail-safe design philosophy by protecting the primary composite structure, a distinct advantage over the laminate-damaging failure modes of bolted joints.