Overview
In the previous blogs, we have introduced the following topics:
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.
Design for integrity in the presence of built-in and accidentally induced stress raisers
Design for structural stability
Design for integrity in a service environment including the effects of humidity and elevated temperature exposure
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
First design decision based on literature/proven design with lightweight design principles as follows
Minimize the amount of material to convey forces
Search for fully stressed designs
Design Stress fields, not components
Avoid bending stresses: girder beams to be decomposed in the truss system
Tension forces can be conveyed over long distances and compression forces over short distances
Short-circuiting forces reduce the use of resources
New design exploration only when existing designs do not meet the requirements
Skin design
Internal member design
Joining interface design
Design for manufacturing review
Any changes/consideration- return to step 1 (structural design)