Fabrication and Mechanical Properties of Multidimensionally (X-D) Braided Composite Materials

Abstract

This paper describes research concerning the resin impregnation and characterization of multidimensionally braided fiber-reinforced composite materials. These materials are an alternative to traditional laminated structures, having the potential for being more damage tolerant. Three graphite fiber systems were used in this investigation, and three processes were investigated for resin impregnation of the multidimensionally braided material using vacuum or pressure. Two were resin transfer techniques and the third was a resin film lamination technique. While all three methods are presented, the latter technique was chosen for impregnating the test specimens due to the consistently low void content and superior surface quality achieved by this method. Three variables having an important bearing on the performance of braided materials were investigated. These included the effect of braid pattern, tow size, and edge condition on the tensile, compressive, flexural, and interlaminar shear properties. The properties were obtained in the braid direction only. The cutting of the specimen edges substantially reduced both tensile and flexural strengths and moduli. Of the three braid patterns investigated (1 × 1, 1 × 1 × 1/2F and 3 × 1), the 3 × 1 braid showed superior tensile performance and the 1 × 1 × 1/2F pattern exhibited superior flexural properties. Variation in fiber tow size caused variations in tensile, flexural, and short-beam shear properties. The 12K tow size specimens exhibited the best performance. All braided composite materials in the uncut edge condition showed significant improvements in their short-beam shear strengths, being equal to or greater than unidirectional laminated composites. This latter characteristic may be one of several indicators that multidimensionally braided composites are inherently damage tolerant.

Quasi-static and fatigue tensile behavior of a 3D rotary braided carbon/epoxy composite

“…Particularly, experimental studies of Macander et al 9 and Gause and Alper 10 provide a lot of data for such comparison. Some results from reference [9] can be also found in reference [11]. Table 4 provides a summary of data for the present material, four materials fabricated and tested in reference [9], and two materials fabricated and tested in reference [10].…”

“…Some results from reference [9] can be also found in reference [11]. Table 4 provides a summary of data for the present material, four materials fabricated and tested in reference [9], and two materials fabricated and tested in reference [10]. High temperature cure epoxies were used in reference [9] (Cytec 5208) and reference [10] (Hercules 3501-6).…”

“…It is seen that the fiber volume fraction varies in a quite broad range, from 55.6 to 68%. Only the apparent braid angle values, determined on the specimen surface, were provided in references [9,10]; they are shown in Table 4; internal braid angles for those materials are unknown. For the present material, apparent braid angle is 10 .…”

“…There are many experimental studies of different static mechanical properties of braided composites, including 3D braided ones, see references [9][10][11][12][13] and more recent publications. 4,6,7 At the same time, only few papers deal with fatigue testing of braided composites.…”

Mechanical Properties of Multidirectional Fiber Composites

“…One of the advantages of these composites is that there is no matrix-dominated property [34,35]. Ko and other investigators [36][37][38][39][40][41][42][43][44][45][46] have made important progress in the fabrication and analyses of three-dimensional braided structures.…”