Exploration relation between interlaminar shear properties of thin-ply laminates under short-beam bending and meso-structures

Abstract

Carbon fiber reinforced polymer matrix composite laminates with standard thickness plies (0.125 mm) usually have weak interlaminar shear strength, meanwhile, for thin-thickness laminate structures such as aircraft wing skin, it is difficult to design a balanced laminate with the standard plies. It is a possible way to improve the interlaminar shear performance of carbon fiber reinforced polymer composite laminates and enlarge the design space of the thin-thickness structures by using thin-plies technology. In this paper, the interlaminar shear strength of carbon fiber/epoxy laminates with thin prepreg thickness subjected to short-beam bending is investigated. Unidirectional, cross-ply and quasi-isotropic laminate specimens were prepared by using prepregs with different ply thicknesses. Results show that, with decreasing of the ply thickness, higher interlaminar shear strength and smaller coefficient of variation of the data are obtained. Compared to laminates made by standard thickness prepreg, the laminates with thin-thickness prepreg exhibit more homogeneous microstructures and more regularly interlaminar shear stress distribution. This indicates that inherent anisotropy of the laminate composites is weakened in the thin-ply laminates and show pseudo-isotropic behavior. Especially in the case of ply thickness less than 0.020 mm, the interlaminar shear stress distributions of the cross-ply and quasi-isotropic laminate are almost the same with that of isotropic materials according to the classic laminate theory. On the other hand, as expected, the design space of the thin-thickness laminate structures will be increased since more ply number are allowed and superior interlaminar properties can be obtained due to the pseudo-isotropic behavior of the thin plies.

Thin-ply polymer composite materials: A review

“…The enhanced longitudinal compressive strength can be considered one of the main contributors to the improved compressive plain strength of multi-directional laminates with thin plies [6,14,15]. However, the enhanced ILSS measured from UD coupons is not expected to have a major role on the ILSS of multi-directional laminates, since the effect of ply thickness on the inter-laminar stress distribution [7] is considered the dominant effect on the improved inter-laminar shear performance of multi-directional thin-ply laminates, overwhelming the micro-structural effects observed on UD laminates. For example, Kalfon-Cohen et al [16] tested blocked (thick baseline) and dispersed (thin baseline) laminates manufactured from the same thin-ply composite system, obtaining higher ILSS on the thin baseline.…”

“…Micro-structural uniformity has also potential effects on the inter-laminar properties of composites. Not only the inter-laminar shear strength (ILSS) of UD laminates increases (in the range of 30%), but also the coefficients of variation of the ILSS data decrease with decreasing ply thickness [7]. Both effects were attributed to the more uniform micro-structure and smaller interlaminar resin-rich regions of thin-ply laminates (Fig.…”

“…Both effects were attributed to the more uniform micro-structure and smaller interlaminar resin-rich regions of thin-ply laminates (Fig. 1) [4,7].…”

Interlaminar shear properties of nanostitched/nanoprepreg aramid/phenolic composites by short beam method

“…25 On the other hand, it was identified that decreasing the prepreg ply thickness resulted in increasing the interlaminar shear strength due to the pseudo isotropic behavior of the thin prepreg ply. 26…”

“…25 On the other hand, it was identified that decreasing the prepreg ply thickness resulted in increasing the interlaminar shear strength due to the pseudo isotropic behavior of the thin prepreg ply. 26 The interlaminar shear strength of ceramic/silicon carbide (SiC) and SiC/SiC was obtained by using the double-notch shear method. 27 However, it resulted in low shear strength due to stress concentration around the notch regions.…”