Analysis of matrix properties on ballistic mechanisms of aramid fabric composites: From experiment to numerical simulation

The matrix employed in the manufacture of composites significantly affects ballistic performances. However, the influence of mechanical properties of the matrix on ballistic mechanisms of composites has still not investigated thoroughly. Polyurethane, as a commonly used matrix, can be designed for various mechanical properties by modulating hard segment (HS) contents. In this work, polyurethanes with different HS contents (HSx-PUs) were prepared as matrix to investigate the ballistic mechanisms of the composites. The thermal and mechanical properties of the HSx-PUs were characterized. The HSx-PUs exhibited increases in the modulus and tensile strength but decreases in the elongation at break as the HS contents increased, and the mechanical properties transformed from soft and tough (HS45-PU and HS55-PU) to rigid and brittle (HS65-PU and HS75-PU). Moreover, quasi-static tests, ballistic test, and numerical simulation were integrated to explore the ballistic performances and mechanisms of aramid fabric reinforced HSx-PUs composites (HSx-PU/AF). The results revealed that the ballistic performances of HSx-PU/AF laminates exhibited an S-shaped growth trend as the HS content decreased. Compared with the HS65-PU/AF and HS75-PU/AF composites, the soft and tough HS45-PU and HS55-PU matrix can help to reduce delamination damage which can force more fibers to combine with each other, thus facilitating energy absorption of the composites. Moreover, the HS45-PU and HS55-PU matrix can reduce the modulus of the composites, which enabled matrix to deform with the fibres during penetration and improved the ballistic performances.