Applied Composite Materials最新文献

Although development of high char-yielding polymers has reduced the manufacturing costs of carbon/carbon composites associated with multiple densification cycles, manufacturing highly customized complex-shaped carbon/carbon composites can still be expensive due to molds/tooling surfaces used by traditional preform production techniques. In this study, we explored whether extrusion deposition additive manufacturing (EDAM) could be used as a mold-less approach to manufacturing complex-shaped carbon/carbon composites. The thermogravimetric analysis and coupon distortion results of several short carbon fiber-reinforced thermoplastic polymers used for 3D printing were investigated, including polyphenylene sulfide, polyetherimide, poly sulfone, polyether ether ketone, and polyether sulfone. Although polyetherimide had the highest char yield (left(57 wt.%right)), carbon fiber-reinforced polyphenylene sulfide was the best preform for manufacturing complex shapes because of its dimensional stability, with carbonized strains of (-4.18times{10}^{-2}) and (1.82times{10}^{-1}) at 1 (^circ C/min) in the 1- and 3- direction, respectively, after heat treating to (900;^circ C). The distortion results of more complex shapes showed that EDAM can be a practical alternative over more traditional preform production techniques for manufacturing complex-shaped carbon/carbon composites.

The present study focuses on the effect of CNT nanofillers on the interlaminar static and fatigue crack propagation in carbon fiber reinforced composite laminates. Multi-walled carbon nanotubes (MWCNTs) were dispersed over the laminate interface through solvent spraying technique. The mode I fracture toughness and R curve behavior were determined first from DCB specimens. Then, the fatigue tests were performed at different stress ratios for laminates containing different contents of CNTs to determine the delamination growth rate da/dN from fatigue crack growth (FCG) curves. When FCG curves are expressed as a function of G, where G is the energy release rate, the growth curves are dependent on the R-ratio. It was found that the addition of CNTs enhances the delamination resistance in the initial part of FCG curves, i.e. low cyclic region. As the test progresses, the effect gradually diminishes making nanofillers ineffective. It is then shown that the FCG curves can be characterized when crack growth rates are expressed as a function of the crack‐driving force (overline{Delta kappa }) used in the Hartman‐Schijve equation. Therefore, the present paper presents a methodology to account for the stress ratio effect to evaluate the crack growth rate for any given R-ratio and to obtain a valid, upper-bound FCG rate curves in CNT reinforced laminates that exhibit high degree of scatter.

Woven lattice truss sandwich panel (WLTSP) has excellent debonding resistance, but is limited to the weak core shear performance. To relax the limit of mono-layer thickness and improve the shear rigidity, foam-filled double-layered WLTSPs (FDWLTSPs) were designed and manufactured by vacuum infusion process (VIP), hot-pressing technology (HPT) and filling-foam technique. Flatwise compression and edgewise compression experiments were performed to reveal the composite effects of multi-layered and filling-foam techniques on the mechanical performances of WLTSP. The results show that the strength, stiffness, and energy absorption of FDWLTSPs are significantly improved. The flatwise compression strength of FDWLTSPs is 5.03 MPa, increased by 403%. The edgewise compression strengths of FDWLTSPs with warp-warp, weft-warp, and weft-weft core arrangements, are 21.97 MPa, 24.1 MPa, and 25.63 MPa, increased by 310%, 283%, and 165%, respectively. The failure patterns of coupling of core compression and shear in flatwise compression and those of buckling and face fracture in edgewise compression were revealed.