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Quick step-by-step guide for Composites design

Updated: Jan 5


In the previous blogs, we have introduced the following topics:

  1. The challenges of switching to composites design

  2. State of the art in composites design for manufacturability

Continuing from the previous blog, this blog highlights the fundamentals of composites design and provides a step-by-step guide for achieving such a design. The key difference of the approach presented here is that it considers manufacturing and material as an integral part of the design process. The table of content is provided below with the links to quickly jump to respective sections:

Fundamentals of design thinking in composites

The two basic decisions in designing a composite part are the selection of materials and the form of construction to be employed. This blog outlines the design requirements, constraints, principles, and decisions.

The materials choice is a compromise between technical, manufacturing, commercial and strategic factors. The form of construction is chosen to obtain substantial weight savings at acceptable manufacturing cost, paying particular attention to four technical factors that dominate the design.

  1. Design for integrity in the presence of built-in and accidentally induced stress raisers

  2. Design for structural stability

  3. Design for integrity in a service environment including the effects of humidity and elevated temperature exposure

  4. Design and test margins to give adequate allowance for anticipated variability of structural performance.

Steps in the process flow of designing the composites part

1. Set out a program objective

  • To design, develop, manufacture, and demonstrate by testing parts made from composites

  • To embody design principles and methods of manufacture that are likely to be adopted for small to medium-volume production to:

  • Save at least X % of structure weight compared with the corresponding structure in the existing metallic shape

  • Embed sensor for Structural health monitoring

  • Combine multiple smaller components into a single large component

  • Integrate with the digital supply chain by automating and digitizing the workflow

  • To maintain standards of safety at least equal to the present metal part and embody design principles to satisfy future damage tolerance requirements

  • To embody materials and manufacturing methods suitable for evolution into cost-competitive structures.

2. General design requirements and their implications

  • The main structure will be able either replace or would adapt to the new design of the assembly

  • Boundary geometry identical to the metal part;

  • Key features for operations

  • Mounting points

  • Moving elements/hinges and sensors

  • Load cases

3. The operational environment and design criteria

  • Environmental degradation

  • Variability and safety margins

  • Notch sensitivity and damage tolerance

4. Key attributes to keep in mind for lightweight structure design

  1. First design decision based on literature/proven design with lightweight design principles as follows

  2. Minimize the amount of material to convey forces

  3. Search for fully stressed designs

  4. Design Stress fields, not components

  5. Avoid bending stresses: girder beams to be decomposed in the truss system

  6. Tension forces can be conveyed over long distances and compression forces over short distances

  7. Short-circuiting forces reduce the use of resources

  8. New design exploration only when existing designs do not meet the requirements

  9. Skin design

  10. Internal member design

  11. Joining interface design

  12. Design for manufacturing review

  13. Any changes/consideration- return to step 1 (structural design)

5. Choice of materials, manufacturing with structural analysis