Identifying the Problem The lack of preferential anisotropic reinforcement in “mainstream” composites has provided motivation to develop materials with multidirectional strength components. Many multidirectional systems exhibit delamination as a primary mode of failure. Three-dimensional (3D) weaving solves both problems--but so far the composite manufacturer and weaver don’t fully communicate each other’s needs.

Traditional 2D Weaving

Processing of 3D Woven Preforms

Typical 3D Woven Geometry

Preform Variables fiber type (IM7, AS4) yarn size (3k, 6k, 12k) yarn distribution (%0°, %90°, %z) weave construction, particularly the placement of the weavers (in-phase or out-of-phase) yarn spacing (yarns per inch) fabric weight (oz/yd 2 ) fiber volume fraction (V f ) weave angle

Typical Constituents of 3D Woven Preforms Most commonly used are graphite tows, with availability the limiting factor in many cases.

Preform Input Parameters Using fiber volume (V f ), thickness (t), ply percentages (wt%) as inputs: Here  is fiber density for each n fiber type and w is the preform areal density. Yarn spacings needed for each i th system (warp, fill, weaver) can then be found using the tow linear density N:

Weave Angle Projection

Determining Preform Thickness Requirements Tows required to meet thickness can be estimated assuming a common aspect ratio (AR): a bd

3D Woven Preform Case Study Two sample preforms were specified, each with a 45°weave angle requested: The preforms were procured from a weaver, then evaluated based on the design methodology.

Example Calculations Example Calculations for Sample 2, using IM7-12k graphite tows for all inputs:

Applying the Methodology Sample 1 Sample 2

Measuring the Weave Angle

Examining Volume Fraction from Input Parameters Evaluating Sample 2: It was calculated that 74.3 oz/yd 2 was needed to meet the 56% volume fraction specified

Conclusions The methodology has been developed for cross- disciplinary understanding of the key variables in 3D weaving Standardization and increased use of 3D woven preforms should increase the communication between weaver and customer The key for both sides: Understanding each other’s capabilities and limitations