Effect of bending-twisting coupling on the compression and shear buckling strength of infinitely long plates

2017

Composite Structures

Self Cite

Section: Thin-ply Techniquesupporting

confidence: 61%

Buckling strength improvements for Fibre Metal Laminates using thin-ply tailoring

Mania

2017

Composite Structures

Self Cite

“…Some new insights into the relative buckling strength with respect to lamination parameter design spaces are provided, by way of an introduction to an accompanying article [10], which explores in detail the effect of Bending-Twisting coupling on compression and shear buckling strength, and is applicable to the data presented here, as well as to data for Extension-Shearing and Bending-Twisting coupled laminates.…”

Section: Bending-twisting Coupling Is Generally Known To Results In Wementioning

confidence: 99%

On Bending-Twisting coupled laminates

2017

Composite Structures

The definitive list of stacking sequences is presented for Bending-Twisting coupled (ASB0DF) laminates, with up to 21 plies. This class of laminate arises from the ubiquitous balanced and symmetric design rule, but symmetry is shown to be a sufficient rather than a necessary constraint. Each stacking sequence configuration is derived in symbolic form together with dimensionless parameters from which the extensional and bending stiffness terms are readily calculated for any fibre/matrix system and angle-ply orientation. Expressions for ply orientation dependent lamination parameters are also given, together with graphical representations, which demonstrate the extent of the design space. Pseudo Quasi-Homogeneous (ASB0DF) laminates are introduced as an important laminate sub-set, since such laminates have concomitant orthotropic properties, i.e. matching orthotropic or isotropic stiffnesses in extension and bending, from which the isolated effects of Bending-Twisting coupling can be studied.

“…These Note that ply contiguity  2 is an enforced constraint by virtue of the NCF architecture, i.e., the number of adjacent plies with the same orientation can never exceed 2. Column material strength constraints can be related to the extensional lamination parameters, whilst buckling strength can be related to the bending lamination parameters, which is discussed in more detail elsewhere [15]. One set of tapered designs, originating from the single (nNCF =) 5 layer design, and corresponding to one of (nNCF =) 7 layer designs, is illustrated in Figs 5 and 6.…”

Section: Resultsmentioning

confidence: 99%

“…However, the limited number of designs for UD material, which are further reduced in the NCF designs of Tables 2 and 3, necessitates the use of Extension-Shearing and Bending-Twisting coupled designs, as previously considered by Baker[21]. The effect on buckling strength of Bending-Twisting coupling is discussed elsewhere[11,12,15], but detrimental effects can be eliminated to a large extent my minimizing D c   . Such designs are readily determined from the lamination parameter design spaces.…”

mentioning

confidence: 99%

Tapered laminate designs for new non-crimp fabric architectures

Composites Part A: Applied Science and Manufacturing

Almeida

2017

Self Cite

Non-Crimp Fabric (NCF) materials are now available in a range of areal weights and layer architectures, including 0/45, 0/-45, 45/-45 and 0/90, which correspond to the standard ply orientations employed in traditional UD material lay-ups.The benefit of NCF material is generally associated with increased deposition rate, but this advantage may be offset by reduced design freedoms when a specific form of mechanical coupling behaviour is required, layer terminations must be introduced and/or thermal warping distortion eliminated.This article investigates the extent to which new NCF architectures can be tailored to achieve warp free tapered laminates with mechanical Extension-Shearing Bending-Twisting couplings, by single axis (longitudinal) deposition of all ply angles; thus avoiding ply discontinuities that may be introduce in large component manufacture.Lamination parameter design spaces are used to demonstrate the extent of the feasible solutions both before and after applying a laminate tapering scheme. 2 IntroductionDesign issues associated with tapered composite laminates have been comprehensively reviewed in a number of articles [1,2]. These reviews reveal an extensive literature, focussing primarily on delamination initiation and propagation in the region of ply terminations, but also reveal that little attention has been given to the extent to which plies may be dropped without introducing thermal warping distortion and associated changes in mechanical coupling characteristics. Indeed, current tapering schemes tend to consider only short ramps or pad-ups, and few [3] consider thermal warping and the associated locked in stresses. By contrast, tapering schemes for continuous wing or fuselage panel construction, in which only single ply terminations may be necessary between adjacent ribs or ring stiffeners, to satisfy strength and/or buckling constraints, are currently restricted to balanced and symmetric laminate designs. Hence, with few exceptions [4], such designs generally require a minimum of 4 ply terminations to avoid introducing thermal warping distortions; their inherent mechanical Bending-Twisting coupling characteristics can also lead to significant reductions in the compression buckling strength [5]. New joint requirements for aero-elastic tailoring and more efficient manufacturing of composite wing or winglet construction requires a more considered tapering scheme, which has resulted in the recent development of bi-angle non-crimp fabrics (NCF) architectures, consisting of two plies of UD material, one at 0° and the other at either a shallow angle,   20°, or the standard 45° angle, stitched together. The repeating biangle [/0]rT NCF concept [6] has the potential to reduce wet lay-up times by half, in comparison to traditional UD tape. In what follows, a layer (of NCF material) contains 2 plies (of UD material). Ply terminations can also be applied to any layer without 3 changing the Extension-Shearing and Bending-Twisting dominant mechanical coupling, necessary for aero-elastic tailoring of wi...