In the previous blog, we discussed how structural composite design is an extremely complicated task, involving CAD, CAE, and CAM. In this blog, the focus is on structural design tools at different stages of the design process.

Conceptual design
Detailed structural design
Design for Manufacture
Design of tooling

Composites structure designs are challenging due to the wide range of design variables e.g. materials, laminates, interactions. The use of a design tool speeds up the process and allows investigation for an optimal solution through several possible concepts. A design goes through multiple stages, shown in the image below

Design tools

Different tools should be used at different stages of the design process

Laminate design tools
Analytical design tools for structural elements
Finite Element (FE) software for more complex structures
Production design tools

Laminate design

Ply calculation

Determining the Engineering constants e.g. laminate strengths, thermal, hygrothermal expansion coefficients of each ply are some of the first key steps of the design process. Design tools come with a database containing mechanical data gathered for specific laminates. Alternatively, some design software allows the designer to efficiently compute ply properties for possible configurations using micromechanics theories.

Laminate design

Laminated composites are made up of several plies bonded together. Plies may have a different fiber material, thickness, and/or orientation. The laminate design tool is used for finding feasible and efficient laminates for given design constraints such as weight,

cost and geometric constraints.

Laminate evaluation

A laminate evaluation enables the analysis of composite laminates subjected to in-plane loads, out-of-plane loads, and thermal loading. Mainly used for tailoring a stacking sequence and inspecting the laminate behavior layer by layer.

A non-exhaustive list of laminate design tools is provided in the table below

Analytical design tools for structural elements

Analytical design tools assist the conceptual and preliminary design of layered composite structures, where an exact elastic solution can be found. Analytical tools require the input of the composite structure geometry and the loadings as well as the constitutive laminate properties, imported directly from the laminate tool. Analytical design tools offer the possibility to analyze several layered composite structural elements such as:

Homogeneous and laminated plates
Sandwich plates
Stiffened panels
Beams
Curved plates
Cylindrical shells
Bonded joints
Bolted joints

A non-exhaustive list of products and their capability is provided in the table below

Finite Element (FE) software for more complex structures

Finite Element Analysis (FEA) techniques with optimization codes to radically improve the design of complex parts. FEA tools allow for either the importation of lay-up definitions from laminate design tools or the rapid creation of ply lay-ups. These tools provide different failure criteria for specific applications,

Tsai-Hill
Hoffman
Tsai-Wu (with Cowin extension)
Hashin (fiber and matrix)

A good FEA tool can feed results back to the design tool to enable updates to be made that can be rapidly re-imported into the analysis tool with the minimum of re-applying loads and meshes. The below table shows FEA packages that have composite materials capabilities

Summary

The composite design is an iterative process. Understanding design stages and the design tools available, provide a good framework for engineers. One of the key requirements once setting up the workflow is interoperability between design tools, as that makes the design be iterated at a much faster pace with multiple team inputs. In the next blog, we will go into more details about the production design tools.

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This is a summary of an article published originally with the same title. The original article can be found here!

Addcomposites

Addcomposites is the provider of the Automated Fiber Placement (AFP) system. The AFP system can be rented on a monthly basis to work with thermosets, thermoplastic, dry fiber placement, or in combination with 3d printers.