Effect of the manufacturing process on the interfacial properties and structural performance of multi-functional composite structures

Abstract

A composite integral armor (CIA) structure consists of various layers such as ceramics, rubber and polymer composites assembled in a precise sequence to provide superior ballistic and structural performance at low areal density. CIA structures were originally manufactured in a labor-intensive multi-step process. In recent years, vacuum-assisted resin transfer molding (VARTM) has emerged as an affordable manufacturing method for CIA structures. In this paper, the relationship between the manufacturing processes (i.e. VARTM and multi-step) and the mechanical performance of CIA beams is investigated by four-point bend tests. The behavior of the CIA is found to be highly dependent on the mechanism of stress transfer between the layers and the structures are found to fail progressively and provide significant ductility and capacity. The VARTM process is found to produce structures with superior mechanical performance. Moreover, the level of interface adhesion achieved during processing is shown to control the structural behavior of the CIA. Consequently, the Mode I fracture testing of VARTM and multi-step manufactured double-cantilever beams, representative of one interface of the CIA, is characterized. The resistance to crack growth of the specimens is also related to the manufacturing process, with the VARTM specimens achieving the highest fracture toughness.