Mechanical performance of carbon-epoxy laminates. Part I: quasi-static and impact bending properties

Abstract

In Part I of this study, quasi-static and impact bending properties of four aeronautical grade carbon-epoxy laminates have been determined and compared. Materials tested were unidirectional cross-ply (tape) and bidirectional woven textile (fabric) carbon fiber lay-up architectures, impregnated with standard and rubber-toughened resins, respectively, giving rise to 1.5 mm-thick laminates. Quasi-static mechanical properties assessed in transversal mode loading were modulus of elasticity, flexural strength and tenacity at the maximum load, whereas the net absorbed energy was determined under translaminar impact conditions. Two-dimensional woven carbon fiber reinforcements embedded in a rubber-toughened matrix presented the best mechanical performance under static loading. Under dynamic loading conditions, woven fiber fabric pre-forms were favorably sensitive to increasing impact energies regardless the nature of the employed epoxy resin. However, it was concluded that great care should be taken with this material within the low energy impact regimen

Variable cavity volume tooling for high-performance resin infusion moulding

“…Surprisingly, the optimized n value is at its minimum level (six fabric layers); however, even though n and v c are both statistically significant (P > 0.05), their contribution to E b is small (2.35 per cent and 4.02 per cent respectively), and it can again be proposed that variation of process parameters has a more significant effect on the level and quality of the resin matrix, which is more important in determining E b (in this process) than the volume fraction of carbon within the structure. The average value obtained (40.7 ± 0.7 GPa) for the non-optimized process is commensurate with the upper levels expected from a vacuum-assisted resin infusion moulding (VARIM) process (35-40 GPa) [27], but underperforms relative to autoclave processing (42.1-49.3 GPa) [28] and RTM (44 GPa) [28]. The upper value obtained through the non-optimized process (47 ± 1 GPa) (Fig.…”

Recent progress in interfacial toughening and damage self‐healing of polymer composites based on electrospun and solution‐blown nanofibers: An overview

“…Typically, a locus with the severe stress state may lead to early microdamages (e.g., damage nucleation) in PMCs . The inhomogeneity of the stress–strain field and the randomness of the strength–toughness of composite constituents result in the typical failure process of laminated PMCs, such as a progressive failure of microcrack nucleation, matrix cracking, fiber breakage, fiber and matrix debonding, and delamination . The typical damage modes in a cross‐ply PMC laminate are illustrated in Figure ; these include matrix cracking, fiber–matrix debonding, fiber breakage, and delamination.…”

Mechanical performance of carbon-epoxy laminates. Part II: quasi-static and fatigue tensile properties

“…The materials and specimens tested were previously described in Part I. In Part II, all the 65.0 x 27.5 x 1.5 mm 3 tablet-shape tespieces were centrally notched in order to induce a preferential tensile fracture path 5 .…”

“…Figure 2 shows the relative performance of the investigated laminates, where the values of S t , TS, TML t and TDML t50 were normalized, i.e., divided by the corresponding lowest values obtained during the mechanical tests, which are highlighted in Table 1. In Figure 2, when applicable, tensile properties are directly compared to bend results obtained in Part I by Tarpani et al 5 , so that converging and/or diverging data of these two different loading modes can be promptly noticed.…”

“…Part I of this study focused on the quasi-static and dynamic bending properties of several carbon-epoxy composite laminates extensively used in the Brazilian aeronautical industry 5 . The general conclusion was that bidirectional woven carbon fiber fabric array embedded in rubber-toughened epoxy resin is the best option to operate under those conditions.…”