This paper presents the development of an integrated technology concept for the production of semi-structural fiber composite aerospace components with a bio-based hybrid laminate structure. In this context, the high lightweight potential of a variable-axial hybrid fiber-reinforced laminates compared to a multiaxial laminate design is of particular importance. As a demonstrator, a double-shell cabin door based on the cabin door of the ultra-light helicopter CoAx 2D of EDM Aerotec GmbH was redesigned in hybrid bio-based mixed composite construction using selected finite-element method (FEM) simulation and optimization tools, manufactured and characterized. The obtained results illustrate that compared to the reference carbon fiber-reinforced polymer (CFRP) component, the developed bio-based hybrid composite with local tailored fiber placement (TFP) reinforcement has a 30% biomass content, exhibits comparable mechanical properties and significantly contributes to increase energy and resource efficiency significantly.

Fibre-reinforced polymers based on natural fibers, such as flax fibers, exhibit pronounced nonlinear orthotropic material behavior. This presents a significant challenge in finite element analysis (FEA) simulations, as the nonlinear constitutive models available in commercial FEA tools are difficult to apply and fail to capture all the material’s specific characteristics. Relying on initial or reduced secant moduli in linear quasi-static analyses of deformations or stress states can result in inaccurate outcomes and overly optimistic strength predictions, particularly in compression-dominated cases. However, with appropriate modifications, classical laminate theory (CLT) can be adapted for nonlinear analysis. This involves iteratively updating the components of the stiffness matrix for the unidirectional (UD) ply during the calculation process based on the current strain state and stress interactions. This study presents and discusses a computational algorithm for the FEA software ABAQUS/CAE 2019, which incorporates material-related orthotropic nonlinearities and stress-dependent interactions within the CLT framework. The algorithm represents a single-scale material model at the meso level (UD ply) and is based on the concept of orthotropic elasto-damage within the framework of continuum damage mechanics (CDM) theory. Numerical implementation is achieved through a user-defined field (USDFLD) subroutine, accompanied by a pre-processing Python script for managing experimental data, computing data fields, and calculating parameters. As shown below, this type of implementation appears justified compared to a user material subroutine (UMAT) subroutine in terms of computational efficiency and practicality.