TIME-DEPENDENT DAMAGE EVOLUTION IN MULTIDIRECTIONAL POLYMER COMPOSITE LAMINATES BY

Multi-directional polymer matrix composite materials are increasingly used in load-bearing structural applications ranging from primary aircraft structures and automotive parts to rehabilitation of bridges. Long-term durability, characterized by time-dependent degradation in strength (known as creep-rupture) and modulus (known as creep), is an important concern in these applications. Despite the experimental evidence on the influence of time-dependent damage on creep and creep rupture of multi-directional composites, current level of understanding of this is very limited. Hence, the focus of this thesis is to develop a clear understanding of the time dependent evolution of various damage modes and their influence on creep rupture of polymer matrix composite laminates. Hexcel Corporation’s F263/T300 unidirectional composite prepreg was used in this study. Three laminates [0/90/0], [±45/902]s, and [0/902]s were subjected to a wide range of constant stresses at various test temperatures and creep rupture time was recorded. Additionally, the time for appearance of first damage in [90] layer (known as First Ply Failure which influences design) as well as the various damage modes and thei