Effects of band weaving on fiber strength in filament-wound composite structures

Filament winding of composite structures generally causes fiber bands to weave or undulate throughout the structure in a non-periodic fashion, except for hoop-only winding. This causes the filament-wound fiber bands, made from multiple groups of filaments, called tows, to fail below the fiber strength of straight fibers. This fiber failure strength reduction is investigated by performing a finite element stress analysis and developing a strength-of-material type closedform solution for curved fibers. The stress analysis results from both methods are compared to actual test results conducted on single and double type weave patterns. The predicted failure stress from the analysis closely matches the experimental results. Application of this work to filament-wound composite pressure vessels is discussed.