Thermal Prestress in Composite Compliant Shell Mechanisms

Stacey, Jonathan; O’Donnell, Matthew P.; Schenk, Mark

doi:10.1115/1.4042476

Cited by 11 publications

(6 citation statements)

References 24 publications

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“…The inclusion of such effects is straightforward, but beyond the scope of the current analysis. Inclusion of these effects can improve prediction of manufactured performance of similar structural architectures [25,26] and field-dependent curvature changes offer additional avenues to manipulate the energy landscape of the system. In other words, the fields can be used, either in isolation or synergistically, to enhance the tailorability of the lattice.…”

Section: (B) Non-dimensional Formmentioning

confidence: 99%

Bespoke extensional elasticity through helical lattice systems

et al. 2019

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Nonlinear structural behaviour offers a richness of response that cannot be replicated within a traditional linear design paradigm. However, designing robust and reliable nonlinearity remains a challenge, in part, due to the difficulty in describing the behaviour of nonlinear systems in an intuitive manner. Here, we present an approach that overcomes this difficulty by constructing an effectively one-dimensional system that can be tuned to produce bespoke nonlinear responses in a systematic and understandable manner. Specifically, given a continuous energy function E and a tolerance ϵ > 0, we construct a system whose energy is approximately E up to an additive constant, with L∞-error no more that ϵ. The system is composed of helical lattices that act as one-dimensional nonlinear springs in parallel. We demonstrate that the energy of the system can approximate any polynomial and, thus, by Weierstrass approximation theorem, any continuous function. We implement an algorithm to tune the geometry, stiffness and pre-strain of each lattice to obtain the desired system behaviour systematically. Examples are provided to show the richness of the design space and highlight how the system can exhibit increasingly complex behaviours including tailored deformation-dependent stiffness, snap-through buckling and multi-stability.

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Section: (B) Non-dimensional Formmentioning

confidence: 99%

Bespoke extensional elasticity through helical lattice systems

et al. 2019

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“…Owing to mismatch of the thermal expansion coefficient between fibre and matrix materials, thermal residual stress commonly occurs within a composite structure [ 3 ]. Although accumulation of residual stresses can occasionally be beneficial, especially for producing shape-changing bistable or multistable structures [ 4 , 5 , 6 , 7 , 8 ], they are usually detrimental, which may lead to laminate warping, buckling or micro-cracks, which significantly affects the mechanical performance of composite products [ 9 ]. PMCs suffer from breakages of fibre bundles and observations of cracks [ 10 ] due to the exerted large interfacial forces with surfaces coated with cellulose nanocrystals [ 11 ], whose rod-shaped morphology treasures high-aspect ratios, which is common in the case of the studied carbon fibre composites.…”

Section: Introductionmentioning

confidence: 99%

Elastic Fibre Prestressing Mechanics within a Polymeric Matrix Composite

Chen

Wang

et al. 2023

Polymers

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The elastic fibre prestressing (EFP) technique has been developed to balance the thermal residual stress generated during curing of a polymeric composite. The continuous fibre reinforcements are prestressed and then impregnated into a polymeric matrix, where the prestress load is only removed after the resin is fully cured in order to produce an elastically prestressed polymeric matrix composite (EPPMC). Although the EFP is active in improving the static mechanical performance of a composite, its mechanics on dynamic mechanical performance and viscoelasticity of a composite is still limited. Here, we established a theoretical model in order to decouple the EFP principle, aiming to better analyse the underlying mechanics. A bespoke fibre prestressing rig was then developed to apply tension on a unidirectional carbon-fibre-reinforced epoxy prepreg to produce EPPMC samples with various EFP levels. The effects of EFP were then investigated by carrying out both static and dynamic mechanical testing, as well as the viscoelastic creep performance. It was found that there is an optimal level of EFP in order to maximise the prestress benefits, whilst the EFP is detrimental to the fibre/matrix interface. The EFP mechanisms are then proposed based on these observations to reveal the in-plane stress evolutions within a polymeric composite.

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“…Also, the curing process of anisotropic laminates leaves residual thermal stresses behind and can be used to generate the required pre-stress. This has been successfully implemented as a method for reducing the stiffness of compliant shells, as described by Doornenbal (2018) and Stacey et al (2019). In nature, differential growth can result in pre-stress, causing structures to obtain their characteristic shapes (Audoly and Boudaoud, 2002;Goriely, 2017;Lessinnes et al, 2017).…”

Section: Introductionmentioning

confidence: 99%