Effect of locally deposited nanosilica particles on interlaminar fracture toughness of high glass-transition temperature epoxy carbon fiber-reinforced composites

Abstract

This study explores the toughening of fiber-reinforced composite laminates to prevent against mode 1 delamination by using a selective placement of nanosilica particles in only the out-of-tow interlaminar regions of the laminate. In place of a conventional homogenous particle distribution throughout the laminate, “selective toughening” through controlled particle deposition is examined with the objective to increase the nanosilica toughening efficiency. Using a laboratory-scale manufacturing route conceptually similar to a combined prepreg and resin-film process, uni-directional carbon fiber composite laminates containing high glass-transition temperature amine-cured Dow D.E.R. 330 epoxy are produced from both particle distribution configurations. Comparisons are made by double cantilever beam testing for mode 1 delamination fracture energy G1C and by examination of the fracture surfaces. The results show that further nanosilica toughening efficiency is possible with local deposition and toughening compared to the conventional homogenous particle distribution throughout the laminate. For the same total nanosilica particle content in the laminate, the delamination toughening effects are maintained or improved when locally toughened in only the out-of-tow interlaminar regions. For mode 1 delamination initiation and propagation, fracture energy increases in the range of 60% over the untoughened laminates are found for the laminates with a local particle distribution. By comparison, those laminates with a conventional homogeneous particle distribution saw increase of 20–35% over the untoughened laminates. The implications of the localized toughening approach are discussed to provide further guidance in optimizing the use of nanosilica particles and particle toughening in general in composite laminates.