Composites are used in a wide range of products, from low-tech shower stalls to high-tech satellites. Although the design requirements vary greatly among these different products, the basics of the materials and the manufacturing techniques remain the same. The fifth edition of "Composite Basics" by Andrew Marshall covers these basic principles.

Although "Composite Basics" is written primarily for the aircraft homebuilder, even experienced engineers will find it a useful reference. Five of the first six chapter focus on the various materials that make up a composite. Marshall shows how similar grades of materials vary between suppliers, so that sometimes simple substitutions can have catastrophic consequences. He also gives some selection guides, showing for example how to choose between polyesters, vinyl esters and epoxies.

Homebuilders and other hobbyists will find the chapters on manufacturing techniques to be invaluable. Even large companies looking to build inexpensive prototypes would do well to consider these methods. Marshall covers the details of building foam master plugs, including instructions on how to build a hot wire cutter. Tight tolerances can be achieved on composite tools, even without expensive machining and inspection equipment.

The practical advice will make any manufacturing operation run smoother. A few examples include:

• Cover a wet layup with plastic film when using a squeegee to prevent damage to the fabric.
• Caulk can be used instead of vacuum bag sealant tape.
• Use a stethoscope to detect vacuum bag leaks. (That's a great idea - I've spent countless hours, even at large companies like Boeing, trying to track down elusive leaks).

You must be careful with some of the advice, though. For example, Marshall suggests resin content can be measured by burning off in a kitchen oven. No mention is made, however, of the hazardous fumes this will create. As another example, Marshall suggests a compressor tank can be safely used as a vacuum plenum because the vacuum pressure is much lower than the internal pressure the tank is designed for. The failure load under external pressure is much lower, though, so the tank may still fail.

The chapters on design and analysis are definitely for aircraft homebuilders only. Not being familiar with homebuilt aircraft design, I had trouble following some of the discussion. The approach is simplified to such a great extent that engineers are not likely to find much of use in these chapters. Homebuilders should also be warned to follow Marshall's advice and only use these chapters for preliminary design, being sure to have all designs and calculations rigorously checked by someone more familiar with stress analysis. Another option is to thoroughly test the structure, and the final chapter of the book provides some good techniques (assuming, of course, your assessment of the loads is accurate).

The appendices alone are almost worth the price of the book, especially the tables showing glass and Kevlar weave styles. I cannot think of another reference that presents such a concise reference of these materials.

Details: "Composite Basics - 5" by Andrew C. Marshall, published by Marshall Consulting, 1998, ISBN 0-9664540-0-6.
1. The Structural Fibers; 2. Fabrics; 3. Core Materials; 4. Honeycomb Core; 5. Carving and Forming Core Materials; 6. The Resin Matrix; 7. Molding Methods and Tooling; 8. Wet Resin and Honeycomb Cores; 9. Designing Composite Structures; 10. Calculating Stresses and Loads; 11. Adhesives and Bonding; 12. Load Testing Your Structure; A1. Sources of Materials and Information; A2. Glass Weave Styles Cross Reference; A3. List of Kevlar Weave Styles; A4. No More Rivets; A5. Properties of a Few Carbon Fibers and Fabrics; A6. Available Sandwich Panels from M.C. Gill's Inventory