Investigation of the compaction behavior of carbon fiber NCF for continuous preforming processes

Abstract

This paper describes the experimental investigation of the compaction behavior of dry single‐ply and multi‐ply fabric stacks (preforms). Utilizing four biaxial (two 0°/90° and two ±45°) and one triaxial (0°±45°) carbon fiber NCF, differing in weight (300 g/m2, 600 g/m2) and type of stitching (tricot, pillar, hybrid), the influence of compaction speed, pre‐compaction cycles, number of layers, and stacking sequence on compaction force was examined. In contrast to other studies, the area of interest is limited to 40–50% fiber volume content (FVC), which is based on current continuous preforming conditions. The results showed that higher testing speeds result in increased compaction forces. Pre‐compaction cycles (up to 8) significantly reduce (up to 69%) the required compaction forces of preforms for continuous preforming. Furthermore, at an equal total superficial density (1800 g/m2), 6‐ply preforms (300 g/m2 each ply) require 75–88% higher compaction forces than 3‐ply preforms (600 g/m2 each ply). This relation remains constant with decreasing or increasing total superficial density (ply number). Also the stacking sequence of 6‐ply preforms (300 g/m2 each ply) remarkably influences the compaction force, whereby the stitching seam pattern and their alignment (superposition) to each other were the main influencing factors. POLYM. COMPOS., 38:2609–2625, 2017. © 2015 Society of Plastics Engineers

Simulation and Validation of Injection-Compression Filling Stage of Liquid Moulding with Fast Curing Resins

“…The results are comparable to the compaction stresses for carbon fibre NCF presented by Grieser et al [12] and are shown on the data in Fig. 10 as well.…”

“…Measured preform compaction data and derived model with comparable compaction stress presented by Grieser et al[12] …”

Compressibility measurement of composite reinforcements for flow simulation of vacuum infusion

“…The closest sensor (at 20 mm) starts at slightly lower v F because it had less dwell time under load before wetting by infusion, and thus less time for viscoelastic fiber rearrangement . The closest sensor also had the fastest expansion, thus a slightly stiffer (steeper) curve , compensating for the lower v F and ending up at a similar uncompressed v F to the other sensor locations. The differences in initial v F and stiffness between adjacent sensor locations decreases farther from the inlet.…”

“…Many subsequent studies have characterized differences in stiffness, the slope of the compressibility function, analogous to the Young's Modulus in a stress–strain diagram. An extensive review of the literature on compressibility measurement is found in the work by Gutowski and Dillon , which focuses on the dependence of the compressibility on the textile architecture. Composite reinforcements, both dry and lubricated with matrix or other test fluid, exhibit classic time‐dependency characteristics: (1) stress relaxation under load, (2) strain rate dependence, and (3) hysteresis .…”

“…An extensive review of the literature on compressibility measurement is found in the work by Gutowski and Dillon , which focuses on the dependence of the compressibility on the textile architecture. Composite reinforcements, both dry and lubricated with matrix or other test fluid, exhibit classic time‐dependency characteristics: (1) stress relaxation under load, (2) strain rate dependence, and (3) hysteresis . The most discussed cause of this time‐dependency is the nesting, i.e.…”