Interlaminar fracture on epoxy-based composites: A review on fractures, improvements, and futures

Polymer matrix composites are known for their favorable mechanical properties, including high specific strength and stiffness. However, one of their primary structural weaknesses is interlaminar fracture, commonly referred to as delamination. This issue is particularly pronounced in epoxy-based composites, despite their otherwise outstanding properties. To address this challenge, researchers have explored various multiscale reinforcement strategies, incorporating natural fibers, nanomaterials, carbon-based materials, self-healing agents, and fabric reinforcements into these composites. These reinforcements have shown potential in mitigating delamination by enhancing the composite’s through-thickness strength and energy absorption. In addition to the type of reinforcement used, several other factors significantly influence interlaminar fracture behavior. These include the morphology and configuration of reinforcements, loading rate during mechanical testing, environmental aging (e.g., exposure to specific solutions), and post-curing treatments. This review provides a comprehensive overview of recent advancements in improving interlaminar properties of composites, with a particular focus on interlaminar fracture toughness (ILFT), interlaminar shear strength (ILSS), and related mechanical metrics. It also discusses the standard methods used to evaluate ILFT, as well as the effectiveness of various reinforcement techniques in enhancing fracture resistance. Ultimately, the study provides valuable insights into future research directions in this critical area of composite materials engineering.