Enhance Epoxy’s Performance with Reinforcing Materials
Reinforcing fabrics and tapes increase tensile strength, and resist hairline cracks and abrasion, greatly improving the longevity of an epoxy laminate. WEST SYSTEM offers glass tapes, biaxial tapes, glass fabrics, and biaxial fabrics as reinforcing materials for building composite laminates and selectively reinforcing structures.
Fiber orientation is important in determining a laminate’s strength and stiffness. Select the type of weave and orient the fibers to best address the direction of the loads within the structure. It’s easier to figure out what the load direction will be for some structures than it is for others. For example, we’d expect a simple cantilevered beam to be exposed to tension on the top and compression on the bottom, with the loads passing in one direction. Therefore, a uni-directional fabric would be appropriate. Structures that may be exposed to less predictable loads may be better off with a woven reinforcing material that will address loads in multiple directions.
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Epoxy and High-Performance Reinforcing Fibers
It makes sense to use epoxy (rather than polyester) when working with high-performance reinforcing fibers. WEST SYSTEM Epoxy will cure fully at room temperature and doesn’t require a lot of special equipment. This has made epoxy a favorite choice of both professional and casual builders of all kinds of high-performance composites. For more about the role of reinforcing fabrics and epoxy in composite laminates, read James R. Watson’s Fiberglass Reinforced Composites in Epoxyworks magazine.
Determining Epoxy Laminate Thickness
To determine the number of fabric layers required to achieve a specific laminate thickness, divided the thickness desired by the single-layer thickness of the tape or fabric you intend to use.
| Product | Fabric Weight | Single Layer Thickness* |
| 740 Glass Fabric | 4 oz | .008″ |
| 742 Glass Fabric | 6 oz | .010″ |
| 729, 731, 732, 733 Glass Tape | 9 oz | .017″ |
| 745 Glass Fabric | 10 oz | .016″ |
| 727, 737 Biaxial Fabric | 17 oz | .035″ |
| 738 Biaxial Fabric with Mat | 23.9 oz | .042″ |
*Average of multiple layers applied by hand lay-up
Estimating Epoxy Coverage for Fabric Application
Below is an estimation of how much epoxy is needed to wet out 1 sq. ft. of fiberglass cloth and apply two fill coats.
| Fabric Product Number | Fabric Weight Per Yard* | Mixed Epoxy Needed |
| 740 Glass Fabric | 4 oz | 1.4 fl. oz. |
| 742 Glass Fabric | 6 oz | 1.61 fl. oz. |
| 729, 731, 732, 733 Glass Tapes | 9 oz | 1.94 fl. oz. |
| 745 Glass Fabric | 10 oz | 2.05 fl. oz. |
| 727, 737 Biaxial Fabric | 17 oz | 2.81 fl. oz. |
| 738 Biaxial Fabric with Mat | 23.8 oz | 3.55 fl. oz. |
*Includes 15% waste factor.