Enhancement of interfacial fracture toughness of carbon/epoxy composite adhesive joints by in-mold surface preparation

Abstract

To reduce secondary processing such as sanding or chemical etching in the manufacture of composite structures, we present an in-mold surface preparation process using imprint lithography on carbon/epoxy composite adhesive joints. In the proposed in-mold process, microstructures are designed and fabricated on the surface of the mold to form composites. Through the formation of composites on the mold at an appropriate temperature and pressure, the shapes of the microstructures are imprinted onto the surface of the composite. Because molding and surface preparation can be performed simultaneously, the time and costs required are reduced compared to conventional surface preparations. In this paper, concavo-convex microstructures were fabricated on the surface of carbon/epoxy composites using in-mold surface preparation, which improved the apparent mode I fracture toughness of the composite/adhesive interface. From double-cantilever-beam tests, we confirmed that as the aspect ratio of the concavo-convex microstructures increased, the steady-state fracture toughness increased by up to 113% compared to structures without in-mold surface preparation, and the fracture mode changed from interfacial failure to complex cohesive adhesive failure.

Keywords

• Polymer composites
• Processing technologies
• Adhesion
• In-mold surface preparation
• Imprint lithography