Enhanced fracture toughness of nanostructured carbon‐fiber reinforced poly(urethane‐isocyanurate) composites at low concentrations

Abstract

Carbon fiber reinforced poly(urethane‐isocyanurate)‐nanosilica composites CF‐(PUI‐NS) were manufactured by means of the vacuum‐assisted resin transfer moulding technique (VARTM) at very low NS concentrations (0–4 wt%). The high strain to failure of the PUI matrix (>7%) affected tensile tests by CF reorientation. Both the tensile strength and strain to failure were highly dependent on its kinematics. CF(PUI‐NS) caused an increase of the static toughness with a maximum improvement of tensile strain to failure and modulus of +28.8% and +39% at 1 wt% and 2 wt% of NS, respectively. The interlaminar shear strength (GIC) of the composites showed both a deterioration of −12.9% and an improvement of +9.9% for NS concentrations of 1 wt% and 4 wt%, respectively. Regardless of the GIC value, all of the composites prepared with NS presented secondary maxima of the force versus displacement plots, indicating a substantial arrest of the crack propagation velocity after delamination started. Fractographic analysis revealed several features, such as fiber pull‐out, bridging as well as river patterns whereas the composites prepared with NS behaved in a more ductile fashion due to the presence of river patterns and a reduced fiber pull‐out. POLYM. ENG. SCI., 58:1241–1250, 2018. © 2017 Society of Plastics Engineers

The role of post‐cure cycle on the thermomechanical properties of soy‐based polyurethane thermosets

“…As already reported in previous studies, 47,48 such a change of the fracture surface was expected due to the change of the microstructure of the thermoset polyurethane. These results are in agreement with what would be expected for a polyurethane thermoset of these characteristics, whereas the fracture behavior was clearly dependent on crosslinker content 49 …”

“…These results are in agreement with what would be expected for a polyurethane thermoset of these characteristics, whereas the fracture behavior was clearly dependent on crosslinker content. 49 As previously described the quasi-static mechanical tests (Section 3) and in particular in Table 2, a sharp decrease in flexural strength, flexural modulus, and flexural strain has been detected for all TSPU-GLI20 samples for post-cure cycles above 160 C. Micrographs of the fracture surface of those samples revealed the formation and propagation of cracks from seemingly spherical shaped defects, such as the ones depicted in Figure 7. Hence, it might be argued that the formation of those defects might be the cause of such detrimental effects on the mechanical properties.…”

Mejora en el comportamiento a la fatiga de compuestos nanoestructurados bidireccionales de fibra de vidrio y poliuretano bajo cargas uniaxiales y altas deformaciones

“…El análisis de la microestructura de las probetas se realizó mediante micrografías SEM de muestras obtenidas en zonas representativas, siguiendo los lineamientos de trabajos anteriores del autor [14,15]. La preparación de ésta consistió en su inclusión en acrílico y su posterior lijado y pulido teniendo en cuenta que para poder observar adecuadamente el refuerzo, cada probeta se rotó en 45°.…”

Significant enhancement of mechanical properties for glass fiber fabric‐reinforced polyamide 6 composites by improving interfacial bonding

“…[36][37][38] However, achieving proper fiber impregnation in fiber fabric-reinforced thermoplastic composites can be challenging due to the high viscosity of thermoplastic materials in traditional hot-press molding processes. To solve this problem, vacuum-assisted resin transfer molding (VARTM) [39][40][41][42][43][44][45][46] has been considered an efficient fabrication method. It involves impregnating the fiber fabric with low-viscosity polymer monomers and subsequently polymerizing them in-situ.…”