Out-of-plane ply wrinkling defects during consolidation over an external radius

Abstract

a b s t r a c tIf carbon fibre layers are prevented from slipping over one another as they consolidate onto a non-trivial geometry, they can be particularly susceptible to wrinkling/buckling instabilities. A one dimensional model for out-of-plane ply wrinkling during consolidation over an external radius is presented. Critical conditions for the appearance of wrinkles provide manufacturing strategies to eliminate such defects. Predicted wrinkle wavelengths and critical wrinkling conditions show good agreement with wrinkle defects observed in a spar demonstrator.

Process Induced Defects in Liquid Molding Processes of Composites

“…Fiber misalignment defects not only disrupt the even distribution of fiber and resin, but also detrimentally impact the properties of composites (Dodwell et al, 2014). Therefore, understanding their formation mechanisms is essential for reducing their occurrences in LCM.…”

“…Formation of these defects at a curvature region is simply a function of the geometry chosen in the design process. Although waviness can theoretically be formed through this mechanism, most practical geometries induce local wrinkling in LCM (Dodwell et al, 2014;Khan et al, 2015). For instance, wrinkling is commonly reported and most critical in the thick, load carrying sections of wind turbine blades, such as the spar caps (Altmann et al, 2015;Bloom et al, 2013).…”

Manufacturing Process Simulation – On Its Way to Industrial Application

“…The high level of complexity does not allow analytical studies. Only the application of sophisticated MPS that is capable of capturing the named phenomena enables the prediction of the manufacturing outcome (Dodwell et al, 2014).…”

“…If the tool-part-interaction is included in the simulation, these influences can be predicted and accounted for during tooling optimization. Furthermore, the fiber wrinkling risk due to consolidation over convex radii may be evaluated, when interlaminar friction is considered as well (Dodwell et al, 2014).…”

Chevron folding patterns and heteroclinic orbits

“…In fact the shear parallel to the layers is in general much weaker than the shear stiffness orthogonal layers. For cases in which there are large disparities, models must not only consider the anisotropic nature of shear at the interfaces, but also the individual contributions of layers as they bend (see for example [22,13,14]) . In other words, the difference in shear parallel and orthogonal naturally leads to non-symmetry in the shear stresses introducing moments per unit area or coupled-stresses.…”