Evaluation of Macroscopic and Local Strains in a Three‐Dimensional Woven C/SiC Composite

Abstract

Engineering tests and full-field strain measurements are used to assess the accuracy of predictions made by the Binary Model, a computational tool for textile composites. The test case is a carbon fiber/SiC matrix composite, in which the reinforcement is a three-dimensional angle-interlock weave. The test composites are thin, having been designed for heat exchanger applications. The thinness leads to strong variations in local strains and strong effects of tow waviness upon macroscopic elasticity. The model performs well in predicting both local variations in strain and macroscopic elasticity. The effect of averaging local strains over variable gauge lengths is explored. Strains averaged over an appropriate gauge length have recently been proposed as the preferred measures of strain for use in local failure criteria.

An elastic–plastic constitutive model for ceramic composite laminates

“…The porous, cracked matrix is homogenized and represented by an iso- Taken together, these results imply that, although the matrix in fully-dense form would be very stiff, its effective modulus is significantly less than that of the fibers (E m =E f % 0:16). Similar results have been reported for a 3-D woven C/SiC composite [32], in which the SiC matrix was processed using similar methods (precursor impregnation and pyrolysis (PIP) and slurry infiltration). In this material, the effective matrix modulus was roughly 15 GPa: an order of magnitude less than the modulus of dense SiC.…”

Quasi-Static Folding and Deployment of Ultrathin Composite Tape-Spring Hinges

“…Following [19], the maximum fiber strain was obtained by computing the average fiber strain in a moving window with a width equal to half a tow width and then selecting the maximum average value. Similarly, the maximum resin strain was obtained by computing 1) the maximum half-tow average normal strain in the direction perpendicular to the fibers in the same moving window and 2) the maximum average principal strain in the resin filling the space between the two plies, and then choosing the maximum of the two.…”

Stochastic Virtual Tests for High-Temperature Ceramic Matrix Composites

“…Such measurements include those via optical microscopy (108)(109)(110)(111)(112)(113), scanning electron microscopy (114-119), speckle interferometry (120)(121)(122), acoustic waves (123)(124)(125), and electrical resistance (126,127). Most of these measurements were at room temperature; only a few studies tackled in situ measurements at high temperatures (e.g., References 114 and 128).…”

“…The situation is further complicated by the presence of fiber coatings, essential for damage-tolerant behavior, whose thermoelastic properties are again uncertain. In one study, SiC matrices formed by a combination of CVI and polymer precursor reaction around coated carbon fibers were deduced by analysis of composite elasticity to be more than an order of magnitude more compliant than monolithic SiC (122).…”