Interlayer toughening of composite materials

Abstract

This article describes the efforts that led to the development of low‐cost interlayer materials that may be used to significantly improve the compression‐after‐impact strength of composite laminates and to, correspondingly, dramatically reduce the area of damage because of impact. Moreover, with the proper selection of the interlayer material, other mechanical properties such as open‐hole compression and shear strength are unaffected or improved over laminates made from identical materials, but without the interlayer. These interlayer materials comprise very lightweight nonwoven veils that may either be melt‐bonded or knitted into noncrimped unidirectional and multiaxial fabric forms using commercial, production equipment. Other than some nominal set‐up costs, these materials add nothing to fabric manufacturing costs than the cost of the materials themselves. Fabrics made using the interlayers may be handled and infused with resin in exactly the same manner as fabrics without the interlayer veils. Proper selection of the veil material is essential, however. An improperly selected interlayer veil material can significantly reduce a composite material's performance. This technology represents a key enabler for the use of low‐cost vacuum‐assisted resin transfer molding processes, low‐cost preforms, and liquid‐molding resins to supplant prepreg as the building‐block material of choice for composite structures. Details of the test methods, results, and conclusions are contained herein. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers.

Interlayer toughening mechanisms of composite materials

“…The main idea of film interleaving methods is to introduce a continuous crack deflection media into the interlaminar planes (Tsotsis, 2009). Planar addition of reinforced or nonreinforced thermoplastic/thermoset polymer films has been considered extensively since the beginning of the 1990s until the early 2000s (Ishai et al, 1988;Masters, 1989;Aksoy, 1991, 1992;Ozdil and Carlsson, 1992;Li et al, 1996;Duarte et al, 1999;Sohn et al, 2000;Jiang et al, 2001;Xuefeng et al, 2002).…”

Nanofibre bridging as a toughening mechanism in carbon/epoxy composite laminates interleaved with electrospun polyamide nanofibrous veils

“…Regular fibrous veils, with a larger diameter of the fibres compared to nanofibrous veils, have also been investigated to study the interlaminar toughening effect [23e26]. The Mode I and Mode II interlaminar fracture toughness, G Ic and G IIc respectively, are most often studied since they can be used to assess the damage resistance of composite laminates [23,24,27]. Indeed, one of the most encountered forms of damage in composite applications is the propagation of cracks through the interlaminar region between reinforcing plies or other dissimilar interfaces where a resin rich layer is present, resulting in delaminations.…”

Improved fatigue delamination behaviour of composite laminates with electrospun thermoplastic nanofibrous interleaves using the Central Cut-Ply method

“…Increasing the delamination resistance of these materials results in higher damage resistance and improved performance and lifetime. Hence, many methods of interlaminar toughening have been proposed and researched over the past decades [1][2][3][4][5][6][7][8][9][10][11][12]. The more recent principle of interleaving composite laminates with electrospun nanofibrous veils has shown to be a viable interlaminar toughening method [13][14][15][16][17][18][19][20].…”