Continuous Tow Steering Around an Elliptical Cutout in a Composite Panel

Abstract

Cutouts are widely used to accommodate windows, openings for access purposes, or fasteners in the primary structural parts of airplanes. The presence of cutouts in composite panels results in stress or strain concentrations, leading to potentially reduced load-carrying capacity. Steering tows around cutouts using emerging techniques in three-dimensional (3-D) printing and advanced fiber placement can potentially alleviate such problems. Continuous tow steering around cutouts also eliminates fiber cutting, thereby precluding ply-level 3-D stress concentration, which could otherwise lead to delamination-induced damage. This work examines stress and strain concentrations, using continuous tow steering, around a representative wingbox access hole. Buckling response under compression loading together with stress and strain concentrations under both tensile and compression loads are examined. A steered configuration shows a 26% improvement in buckling performance in comparison with the equivalent straight-fiber configuration. Under tensile loading, the maximum stress and strain concentration factors around the cutout are 29 and 32% larger, respectively, for straight-fiber orientations than those with steered tows around the cutout. For the compression loading condition, the direct strain of the panel with straight-fiber orientations was found to be three times that of steered-fiber trajectories in the vicinity of the cutout.

Mechanical Cloaking of Cutouts in Laminated Plates

“…The potential for increasing the performance of holed laminated plates by fiber steering has been investigated by a number of studies [7,8,10]. However, the concept of altogether cloaking, masking or concealing the mechanical effects of cutouts on laminated plates by the fiber steering concept has received little attention.…”

“…Thus, fiber-steered structural research studies have included the presence of cutouts in design studies. Recently, Zucco et al investigated the potential of steering around a central elliptical cutout to achieve an increase in buckling performance when compared to an equivalent straight fiber plate [10]. Zucco et al [10] reported a 26% increase in buckling load for a 17% plate mass increase.…”

“…Recently, Zucco et al investigated the potential of steering around a central elliptical cutout to achieve an increase in buckling performance when compared to an equivalent straight fiber plate [10]. Zucco et al [10] reported a 26% increase in buckling load for a 17% plate mass increase. Moreover, the method for steering material tows around a central elliptical cutout always results in a resin-rich area in close vicinity to the cutout in the direction of steering.…”

3D Printing of Flow‐Inspired Anisotropic Patterns with Liquid Crystalline Polymers

“…[ 5 ] In contrast, despite the larger processing energy and stronger base materials used, human‐made materials such as composites cannot be shaped with similar levels of anisotropy and directionality freedom. [ 6 ] While the latter can be achieved with 3D printing such as fused filament fabrication (FFF), or via automated composite tape laying, [ 7 ] compatible anisotropic materials are typically fiber‐filled. [ 8 ] Paradoxically, these fibers restrict directional freedom due to their intrinsic stiffness and relatively large size.…”

Research of stress concentration at closely placed holes in wing bearing area in anisotropic plates

“…Using this method, stresses near holes of different shapes in composite plates were studied [1,2,4,15,20,22]. In composite elements of aviation equipment, a system of holes is often created.…”