Steady-state cracking and edge effects in thermo-mechanical transverse cracking of cross-ply laminates

Abstract

Composites for space applications such as advanced satellites will require the use of new and/or improved materials so that more stringent dimensional stability requirements can be met. In this work, we study the effect of ply-level initiation of damage under loading and processing stresses and imposed thermal loading. In particular, included in the study is the prediction and demonstration of a condition of steady-state cracking and the temperature change and loading level necessary to create this damage state, thus leading to the possibility of a predetermined loading range over which layer cracking will not propagate. We also consider the influence of the free-edges on the initiation of layer transverse cracking and potential microcracking that may develop at the fiber/matrix interface. The condition of constrained edge cracking is demonstrated where cracks develop but do not propagate across the laminate. To accomplish these studies unidirectional composites and various cross-ply laminates of IM7/5250-4 (graphite/bismaleimide) were produced and characterized.