Thermo-mechanical behaviour of woven cloth laminates

TA Engineering (General). Civil engineering (General)

Shamsudin, Mohd Hafizi ; York, Christopher Bronn

University:University of Glasgow

Department:School of Engineering

关键词: Mechanically coupled laminates, hygro-thermally curvature-stable, standard angle-ply orientations, balanced plain weave, 5-Harness Satin weave;   

Others  :  http://theses.gla.ac.uk/6479/7/2015ShamsudinPhd.pdf

来源: University of Glasgow

【 摘 要 】

Balanced and symmetric laminates are pervasive in design practice for the simple reason that thermal warping distortions are associated with non-symmetric laminate designs. Design practice, particularly in the Aerospace sector, has become entrenched and risk averse, hence the reluctance to move away from this simple design rule. However to unlock the full potential of composite laminates, the coupling interactions between in-plane and out-of-plane, must now be considered. Thermally stable laminates can now be achieved through sophisticated tailoring design strategies, leading to mechanically coupled materials properties with immunity to thermal warping distortion. This unique quality is known as the hygro-thermally curvature-stable (HTCS). The Extension-Twisting (and Shearing-Bending) coupled laminate is one particular class of coupled laminate with HTCS properties, which is an enabling technology for tilt-rotor aircraft. This class of laminate may be derived using standard ply angle orientations i.e. 45, 45, 0 and 90°, which in comparison to free form angle ply orientations, developed through an optimisation technique, will facilitate the requirement for ply terminations, whilst preserving the Extension-Twisting coupling behaviour within the entire laminate tapered design. Free form angle laminates make thickness tapering virtually impossible, particularly if maintaining consistent coupling behaviour within the entire laminate is a design constraint. Extension-Twisting coupled laminates derived from standard angle orientations with HTCS properties are shown to exist only for 8-, 12-, 16- and 20-ply number groupings, and an assessment of the configurations for each twist magnitude and buckling load strength is presented for each case. The limited number of groupings these coupled laminate solutions is shown to be the result of employing unidirectional material.The above restrictions for UD material may be relaxed for laminates with balanced Plain weave material, which are shown to be inherently thermally curvature stable. Balanced Plain weave material results in a broader design space for mechanically coupled laminates; irrespective of the ply angle orientations and ply number grouping. This benefit provides more flexibility for laminate tailoring and thickness tapering; where the mechanical coupling behaviour and immunity to thermal warping distortions is maintained throughout, it also opens up the possibility of changing the coupling behaviour through a novel ply termination strategy. Where standard ply angle orientations are a design constraint, seven unique classes of mechanically coupled laminates exist with interactions between Extension, Shearing, Bending, and Twisting.Alternative woven cloth architecture are also considered. For instance, 5-Harness Satin (5HS) weave material, possesses straighter load-carrying fibres and low crimp angle, gives rise to improve mechanical performance in comparison to Plain weave material, in which maximum fibre kinking potentially exists. However, due to the unsymmetric nature of the 5HS weave architecture, a single layer of this material is shown to be thermally unstable, therefore a method is presented to predict the thermal warping curvature and eliminate their effect by applying suitable lamination strategies.