Abstract

This article compares derivation methods for constructing optimal membrane triangles with corner drilling freedoms. The term “optimal” is used in the sense of exact inplane pure-bending response of rectangular mesh units of arbitrary aspect ratio. Following a comparative summary of element formulation approaches, the construction of an optimal 3-node triangle using the ANDES template is shown to be unique if energy orthogonality constraints are enforced a priori. Two other formulation are examined and compared with the optimal model. Retrofitting the conventional LST (Linear Strain Triangle) element by midpoint-migrating by congruential transformations is shown to be unable to produce an optimal element while rank deficiency is inevitable. Use of the quadratic strain field of the 1988 Allman triangle, or linear filtered versions thereof, is also unable to reproduce the optimal element. Moreover, these elements exhibit aspect ratio lock. These predictions are verified on benchmark examples.

Abstract

Under the coordination of AITEX and in collaboration with the partners of the r-LightBioCom project, intensive research, selection, and validation of sustainable reinforcement fibers (natural, recyclable or recycled, and with low environmental impact) have been carried out for use in composites that will be validated in automotive demonstrators (spoiler and trunk floor), infrastructure (tunnel lining), and aeronautics (wing leading edge). In this area, the following achievements stand out:

1. Validation procedure regarding processability and mechanical characteristics of various sustainable reinforcement fibers (recycled carbon and glass fibers, natural fibers, basalt fiber, and recycled aramid fiber).
2. Development of sustainable textile intermediates (fabrics, mats, pre-pregs, honeycombs, and rovings) through the adaptation of textile technologies for processing the selected reinforcement fibers and compatible with bio-based resins.
3. Hybridization of sustainable reinforcement fibers with virgin filaments to improve mechanical properties while maintaining low environmental impact. The results obtained indicate that the selection of alternative and more sustainable fibers than those usually used in the production of composites are suitable for the development of the aforementioned demonstrators in terms of processability and resistance.​

The results obtained indicate that the selection of alternative and more sustanaible fibers than those usually used in the production of composites are suitable for the develpment of the aforementioned demonstrators in terms of processability and resistance.