scholarly journals Role of contamination on the bondline integrity of composite structures

2013 ◽  
Author(s):  
Xu Shang
Keyword(s):  
Composite Structures

Stiffness-toughness balance in PP/EPDM/SiO2 ternary blend-nanocomposites: The role of microstructural evolution

2020 ◽  
Vol 55 (2) ◽  
pp. 265-275
Author(s):  
S Hajibabazadeh ◽  
MK Razavi Aghjeh ◽  
M Mehrabi Mazidi
Keyword(s):  
Microstructural Evolution ◽  
Composite Structures ◽  
Ternary Systems ◽  
Ternary Blend ◽  
Dispersed Particles ◽  
Stress Concentration Region ◽  
Dispersion State ◽  
Izod Impact ◽  
Blend Nanocomposites

The effect of microstructural evolution with hydrophilic-nanosilica (SiO2) concentration, ranging from 0 to 5 wt%, on mechanical properties and deformation micromechanisms of PP/EPDM/SiO2 (80/20/x) ternary blend-nanocomposites was investigated. Morphological observations revealed that, SiO2 nanoparticles tend to localize either around the dispersed EPDM particles or at the PP/EPDM interface, promoting the formation of three dimentional network-like EPDM/SiO2 composite structures dispersed in the PP matrix, especially at higher SiO2 loadings. This type of dispersion state was further confirmed by the rheological analysis. Synergistic toughening effect of soft EPDM particles and rigid SiO2 particles under Izod impact test was observed in these ternary systems, so that the materials with a better balance of stiffness/toughness were achieved. The results demonstrated that the extent of impact toughness increase is higher, where a large amount of the SiO2 nanoparticles surrounded the EPDM dispersed particles distributed in the PP matrix. This significant increase was attributed to the change in the size of stress concentration region and evolution of stress distribution throughout the material. The failure mechanisms were studied, and the underlying toughening micromechanisms were proposed.

Damage Tolerance of Composite Structures: The Role of Interlaminar Fracture Mechanics

1991 ◽  
Vol 113 (3) ◽  
pp. 247-252 ◽  
Author(s):  
J. W. Gillespie
Keyword(s):  
Fracture Mechanics ◽  
Composite Laminates ◽  
Composite Structures ◽  
Failure Modes ◽  
Damage Tolerance ◽  
Laminated Composite ◽  
Test Methods ◽  
Interlaminar Fracture ◽  
Delamination Growth

Layered fiber-reinforced composite structures are susceptible to crack initiation and growth in the resin-rich layer between plies. Delamination represents one of the most prevalent life-limiting failure modes in laminated composite structures. Interlaminar fracture mechanics represents one approach to assess the damage tolerance of composite structures. This paper is organized into two major sections. The first sections introduces interlaminar fracture mechanics and test methods that have been developed to characterize the Mode I, II and III interlaminar fracture toughness of composite laminates. In the second section, the role of interlaminar fracture mechanics in assessing damage tolerance of composite structures is defined through the following case studies: residual compression after impact strength, instability related delamination growth in compressively loaded laminates and delamination growth in composite laminates with discontinuous internal plies.

The role of material nonlinearities in composite structures

1997 ◽  
Vol 38 (1-4) ◽  
pp. 71-81 ◽  
Author(s):  
W.K. Chili ◽  
S. Galea ◽  
R. Jones
Keyword(s):  
Composite Structures

scholarly journals African Easterly Wave Dynamics in a Mesoscale Numerical Model: The Upscale Role of Convection

2012 ◽  
Vol 69 (4) ◽  
pp. 1267-1283 ◽  
Author(s):  
Gareth J. Berry ◽  
Chris D. Thorncroft
Keyword(s):  
Composite Structures ◽  
Diabatic Heating ◽  
Weather Prediction ◽  
Phase Speed ◽  
Lower Troposphere ◽  
Life Cycles ◽  
Large Contribution ◽  
African Easterly Wave ◽  
Easterly Wave

Abstract To examine the dynamical role of convection in African easterly wave (AEW) life cycles the Weather Research and Forecasting (WRF) model is used to simulate the evolution of a single AEW from September 2004. The model simulations are validated against corresponding numerical weather prediction analyses and the mean fields closely resemble composite structures from previous studies. A potential vorticity (PV) thinking approach is used to highlight the interactions between dynamics and convection. Organized deep convection embedded within the AEW has a large contribution to the synoptic-scale mean PV and energetics of the AEW. The PV tendency is maximized in the lower troposphere, consistent with the vertical gradient in diabatic heating rates in the areas of convection. By examining terms in the Lorenz energy cycle, it is shown that diabatic heating associated with convection is as important as adiabatic energy conversion in producing eddy available potential energy of the synoptic AEW, implying that AEWs are best described as hybrid adiabatic and diabatic structures. The net effect of convection is succinctly described using a simulation whereby the parameterizations associated with convection are switched off at the midpoint of the model run. This perturbation experiment shows that, although the AEW continues to propagate westward with a similar phase speed, the net PV value continually weakens with time. This result proves that convection is vital for the maintenance of the AEW as it propagates across West Africa and suggests that without active convection the synoptic AEW cannot persist for an extended length of time.

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