The microscopic failure processes and their relation to the structure of amine-cured bisphenol-A-diglycidyl ether epoxies

Morgan, Roger J.; O’Neal, James E.

doi:10.1007/bf00561968

Cited by 107 publications

(51 citation statements)

References 68 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…19,20,21,22,23,24 Heterogeneous cross-linking on this scale is expected to provide low energy pathways through the resin, yielding a structural basis for the relatively low fracture toughness of epoxy materials. 25,26 Indeed it has recently been shown that the bulk toughness, solvent resistance, T g , compressive strain to failure and ductility of formation improve when narrow molecular weight distributions are maintained during the cure of epoxydicyanodiamide resins.…”

Section: Insights Into Epoxy Network Nanostructural Heterogeneity Usimentioning

confidence: 99%

Insights into Epoxy Network Nanostructural Heterogeneity Using AFM-IR

Morsch

Liu

Lyon

et al. 2015

ACS Appl. Mater. Interfaces

108

115

View full text Add to dashboard Cite

The first direct observation of a chemically heterogeneous nanostructure within an epoxy resin is reported. Epoxy resins comprise the matrix component of many high performance composites, coatings and adhesives, yet the molecular network structure that underpins the performance of these industrially essential materials is not well understood. Internal nodular morphologies have repeatedly been reported for epoxy resins analysed using SEM or AFM, yet the origin of these features remains a contentious subject, and epoxies are still commonly assumed to be chemically homogeneous. Uniquely, in this contribution we use the recently developed AFM-IR technique to eliminate previous differences in interpretation, and establish that nodule features correspond to heterogeneous network connectivity within an epoxy phenolic formulation.

show abstract

Section: Insights Into Epoxy Network Nanostructural Heterogeneity Usimentioning

confidence: 99%

Insights into Epoxy Network Nanostructural Heterogeneity Using AFM-IR

Morsch

Liu

Lyon

et al. 2015

ACS Appl. Mater. Interfaces

108

115

View full text Add to dashboard Cite

show abstract

“…The load, displacement, and time were simultaneously recorded with a personal computer-controlled data acquisition system during the tests. To reduce the effect of variation of crosslink density on the fracture toughness, 9 the fracture toughness tests in each condition have been repeated five times, and the average K IQ and K IIQ were determined. After failure, the fracture surfaces were examined under both optical microscope and scanning microscope.…”

Section: Materials and Experimental Proceduresmentioning

confidence: 99%

Effects of loading rate and thickness on mixed‐mode I/II fracture toughness of thermoset epoxy resin

Kanchanomai

Rattananon

2008

J of Applied Polymer Sci

View full text Add to dashboard Cite

The influences of loading rate and thickness on fracture behavior and mechanism of thermoset epoxy resin with polyamine hardener under mixed-mode (mode I/II) loading have been studied at low thickness and low loading rate (LTLL), as well as high thickness and high loading rate (HTHL). Under the variation of mixed-mode loading from mode I to mode II, fracture toughness of HTHL specimens were under plane-strain condition. For LTLL specimens, the fracture toughness at dominated mode I loading was under plane-stress condition, whereas those at dominated mode II loading were under plane-strain condition. The stretched zone due to the principal stress in the normal direction to the crack plane as well as shear lips due to the Poisson contraction in the thickness direction were the main characteristic of the fracture surface of LTLL specimen tested at pure mode I loading. On the other hand, the mirror-like fracture surface was observed for the HTHL specimen tested at pure mode I loading. Under pure mode II loading, the aligned stretched zone due to the maximum shear stress was the main characteristic of the fracture surface of LTLL specimen, whereas irregular appearance of the stretched zone was observed for the HTHL specimen.

show abstract

“…Materials of interest have possessed heterogeneities ranging from locally anisotropic grain structures in monoliths such as rocks, ceramics and glass spinels, to particulate and/or fiber-reinforced metals, ceramics and polymers [1, 2,3]. Sources of toughness in these materials can be grouped into two categories, depending upon the location of microstructural events.…”

Section: Statement Of Principal Thesis Objectivesmentioning

confidence: 99%

“…Specimens were taken directly from the storage desiccator and a drop of molybdenum disulphide oil was placed on each end. 3 They were then centered, with a positioning jig, on the similarly-lubricated platens. The data-acquisition system was then activated and the deformation begun.…”

Section: A144 Testing Proceduresmentioning

confidence: 99%

Experimental investigations of crack trapping in brittle heterogeneous solids

Mower

Argon

1995

Mechanics of Materials

View full text Add to dashboard Cite

Over the past two decades many mechanisms of toughening have been considered for brittle solids. Some of the most prominent ones applicable to either monolithic materials or fiberreinforced composites include deformation-induced local transformations, micro-cracking, crack trapping, crack bridging, and fiber pull-out. Few if any of these have been studied in the past in a manner which permitted evaluation of the effects of individual mechanisms in the absence of other interacting mechanisms. Here we present the development, analysis and results of an experimental study of toughening by the process of crack trapping by second-phase particles (spheres and fibers) of such toughness that make them impenetrable by probing cracks, forcing the cracks to bow around the obstacles with increasing applied load.The model fracture specimens employed here were wedge-loaded double cantilever beams cast of a brittle epoxy, containing macroscopic (3mm-diameter) inclusions of Nylon or polycarbonate having similar elastic properties to the matrix. The tests were performed at -60*C to achieve controlled, stable crack propagation. Images of the crack fronts advancing at velocities of about 10-4 M/s were recorded with good resolution, providing a continuous record of crack-front shapes during the evolution of the crack-trapping process from the initial pinning configuration through the transition to crack-flank bridging. Remarkable agreement between these images and crack-front shapes predicted by the numerical simulation of Bower & Ortiz is demonstrated. A parametric approach was adopted to study the influence of obstacle spacing, surface adhesion and thermally-induced residual stresses upon the observed crack-front behavior and enhanced stress intensity required to propagate the cracks past these obstacles. Analysis of the quantitative data has demonstrated that, in brittle matrices containing particle volume fractions of approximately 0.2, toughness enhancement by over a factor of two, relative to neat matrix values, may be achieved through the crack-trapping mechanism alone, provided that a high level of adhesion can be maintained between the matrix and the tough reinforcing particles.

show abstract

The microscopic failure processes and their relation to the structure of amine-cured bisphenol-A-diglycidyl ether epoxies

Cited by 107 publications

References 68 publications

Insights into Epoxy Network Nanostructural Heterogeneity Using AFM-IR

Insights into Epoxy Network Nanostructural Heterogeneity Using AFM-IR

Effects of loading rate and thickness on mixed‐mode I/II fracture toughness of thermoset epoxy resin

Experimental investigations of crack trapping in brittle heterogeneous solids

Contact Info

Product

Resources

About