Abstract
The concept of aligning reinforcing fibers in arbitrary directions offers a new perception of exploiting the anisotropic characteristic of the carbon fiber-reinforced polymer (CFRP) composites. Complementary to the design concept of multiaxial composites, a laminate reinforced with curvilinear fibers is called variable-axial (also known as variable stiffness and variable angle tow). The Tailored Fiber Placement (TFP) technology is well capable of manufacturing textile preforming with a variable-axial fiber design by using adapted embroidery machines. This work introduces a novel concept for simulation and optimization of curvilinear fiber-reinforced composites, where the novelty relies on the local optimization of both fiber angle and intrinsic thickness build-up concomitantly. This framework is called Direct Fiber Path Optimization (DFPO). Besides the description of DFPO, its capabilities are exemplified by optimizing a CFRP open-hole tensile specimen. Key results show a clear improvement compared to the current often used approach of applying principal stress trajectories for a variable-axial reinforcement pattern.
Highlights
The demand for energy efficient systems leveraged the use of carbon fiber-reinforced polymer (CFRP) lightweight composites in structural components
In order to evaluate the capabilities of Direct Fiber Path Optimization (DFPO), to the openhole specimen, the sample consists of two layers, attained by stacking a carbon fiber Tailored Fiber Placement (TFP) layer on top of the base material (± 45∘ carbon fiber woven fabric with areal weight of 256 g.m−2)
The DFPO solution is qualitatively similar to the open-hole solution but with stronger fiber concentration due to the stronger narrowing of the defect (Figure 11(b))
Summary
The demand for energy efficient systems leveraged the use of CFRP lightweight composites in structural components. Spickenheuer et al [1, 29] and Albers et al [30] made initial attempts to separate the optimization process of a curvilinear fiber-reinforced composite manufactured via TFP from the actual numerical models in order to limit the number of required design variables, making them independent of the applied FE mesh resolution. Once a sufficiently accurate modeling of VA fiber layouts is established, optimization techniques can be applied to the fiber pattern This allows fully utilizing the high degrees of freedom in the design process and the maximization of the anisotropic material characteristics of CFRPs. Given the identified gaps in the current state-of-the-art in properly modeling VA composites, this work presents a novel design procedure for illustrating the capability for generating a VA pattern for an open-hole tensile specimen, where an optimal fiber pattern cannot be derived. The novel optimization approach, called Direct Fiber Path Optimization (DFPO) for VA composites, will be introduced and numerically evaluated on the example of an open-hole tensile specimen
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