Abstract:Through-the-thickness stitching of layered composites provides through-the- thickness reinforcement to enhance the interlaminar tensile and shear strengths while maintaining structural continuity. However, under planar mechanical loads, stitched composites develop strain concentrations in the resin rich areas around the stitch seam causing a local reduction in mechanical properties. In this study, nanographene toughened epoxy is used to reduce strain concentrations around stitch seams and increase the global t… Show more
“…Alaziz et al studied the influence of GNP toughening on the tensile response of stitched composites. 85 The tensile modulus and strain energy density were improved by 9.71% and 7.18%, respectively, by the presence of 1 wt% GNP in the modified epoxy. Strain concentrations around stitching sites were significantly reduced, indicating increased energy absorption in those zones under axial deformations.…”
Section: Methods To Reduce Permeabilitymentioning
confidence: 94%
“…Alaziz et al studied the influence of stitching patterns on the tensile response of composites and concluded that the resin rich areas around the stitches form zones of stress concentrations that altered the local properties of these composites. 84,85 With a CTE mismatch between the stitching thread and the resin pocket around it, micro-cracks initiate from these zones that run through the thickness of the specimen along the stitching thread. 35,36 Such crack networks influence the gas permeability of composites and, therefore, need to be reduced to increase the fuel containment performance of composite cryogenic tanks.Figure 6.Cracks initiating from resin columns around through-the-thickness stitches in cryogenically cycled stitched composites.…”
Section: Permeability and Transverse Microcrackingmentioning
Fiber-reinforced polymer matrix composites are increasingly considered for lightweight cryogenic pressure vessels due to their excellent combination of tailorability, specific mechanical properties, and relatively low coefficients of thermal expansion. However, significant challenges must be overcome to fully utilize PMCs for cryogenic fuel tanks in terms of transverse microcracking and subsequent permeation of cryogenic fuel. Gas permeation and microcrack densities of cryogenically cycled composites are highly influenced by their layup, ply thickness, load case, and manufacturing defects like voids and resin rich zones. There has been a significant amount of research on measuring gas permeation of composites fatigued under pure thermal or uniaxial thermo-mechanical stresses. However, results demonstrate that the gas permeability should be measured under biaxial thermo-mechanical stresses to properly gauge the leakage characteristics of damaged composites. This paper summarizes the results from over a hundred papers on the key parameters that influence the gas permeability of composites, appropriate testing methods to cycle composites for permeability measurement, methods to limit the evolution of transverse microcracks, and materials traditionally used for the fabrication of all-composite cryogenic fuel tanks. Thin plies and nanofiller-toughening of the matrix have been shown to provide significant improvements in transverse microcrack suppression within cryogenically cycled composites.
“…Alaziz et al studied the influence of GNP toughening on the tensile response of stitched composites. 85 The tensile modulus and strain energy density were improved by 9.71% and 7.18%, respectively, by the presence of 1 wt% GNP in the modified epoxy. Strain concentrations around stitching sites were significantly reduced, indicating increased energy absorption in those zones under axial deformations.…”
Section: Methods To Reduce Permeabilitymentioning
confidence: 94%
“…Alaziz et al studied the influence of stitching patterns on the tensile response of composites and concluded that the resin rich areas around the stitches form zones of stress concentrations that altered the local properties of these composites. 84,85 With a CTE mismatch between the stitching thread and the resin pocket around it, micro-cracks initiate from these zones that run through the thickness of the specimen along the stitching thread. 35,36 Such crack networks influence the gas permeability of composites and, therefore, need to be reduced to increase the fuel containment performance of composite cryogenic tanks.Figure 6.Cracks initiating from resin columns around through-the-thickness stitches in cryogenically cycled stitched composites.…”
Section: Permeability and Transverse Microcrackingmentioning
Fiber-reinforced polymer matrix composites are increasingly considered for lightweight cryogenic pressure vessels due to their excellent combination of tailorability, specific mechanical properties, and relatively low coefficients of thermal expansion. However, significant challenges must be overcome to fully utilize PMCs for cryogenic fuel tanks in terms of transverse microcracking and subsequent permeation of cryogenic fuel. Gas permeation and microcrack densities of cryogenically cycled composites are highly influenced by their layup, ply thickness, load case, and manufacturing defects like voids and resin rich zones. There has been a significant amount of research on measuring gas permeation of composites fatigued under pure thermal or uniaxial thermo-mechanical stresses. However, results demonstrate that the gas permeability should be measured under biaxial thermo-mechanical stresses to properly gauge the leakage characteristics of damaged composites. This paper summarizes the results from over a hundred papers on the key parameters that influence the gas permeability of composites, appropriate testing methods to cycle composites for permeability measurement, methods to limit the evolution of transverse microcracks, and materials traditionally used for the fabrication of all-composite cryogenic fuel tanks. Thin plies and nanofiller-toughening of the matrix have been shown to provide significant improvements in transverse microcrack suppression within cryogenically cycled composites.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
