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Designing and Optimizing Composite Structures for Automated Fiber Placement Processes

Updated: Mar 7


In this article, we will explore the design and optimization of composite structures in automated fiber placement (AFP) processes. We will discuss the advantages and limitations of constant stiffness and variable stiffness design approaches, as well as design guidelines for optimizing composite structures for AFP production process. We will also cover various layup strategies, including reference curve strategies and coverage strategies, and the concept of coverage density in AFP production process.

In addition, we will delve into the importance of process parameters in ensuring good layup quality and the influence of speed, pressure, temperature, and tension on layup quality. We will also discuss the various defects that can occur during AFP and the importance of online defect detection techniques in ensuring good layup quality. Finally, we will review various methods for assessing the quality of AFP layups after the layup process is complete.

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Designing Composite Structures with Constant and Variable Stiffness: Advantages and Limitations

Composite materials have a range of advantages, such as improved mechanical properties, corrosion resistance, fatigue life, and fracture toughness. However, careful design and optimization are required to fully utilize these benefits. There are two categories of composite structure design: constant stiffness and variable stiffness.

Constant stiffness design uses the same stacking sequence throughout the structure, while variable stiffness design involves changing the fiber angles across the structure to optimize performance. In industry, composite manufacturing is currently limited to using conventional constant stiffness laminates with fiber angles restricted to 0, ±45, and 90 degrees. There are also guidelines for laminate design to ensure robustness, including using symmetric and balanced laminates, limiting the maximum number of consecutive plies, limiting the maximum and minimum ply angle jump, and using ±45-degree surface plies.

Fiber steering capabilities can be used to increase design flexibility and create more efficient composite structures through variable stiffness laminates. However, there are constraints on these designs, including the minimum turning radius of fibers and continuity constraints.

Design Guidelines for Optimizing Composite Structures in Automated Fiber Placement Processes

This table summarizes common design practices for composite structures, including guidelines for balanced and symmetric laminates, ply angle jumps, surface plies, fabric layers, and ply drops to ensure structural integrity and optimize performance.

​Design Practice: Employ balanced and symmetric laminates Effect: Minimizes [B] matrix, avoids bending, coupling, warping, and twisting effects

Design Practice: Maximum number of consecutive plies Effect: Prevents delamination and residual stresses

Design Practice: Maximum and minimum ply angle jumps Effect: Decrease inter-laminar stress and obtain dispersed laminates

Design Practice: ±45-degree surface plies Effect: Increases damage tolerance, buckling load of thin laminates, and protects