scholarly journals Damage Tolerance of Composite Materials Subject to Dynamic Flexural Tests

2000 ◽  
Vol 9 (1) ◽  
pp. 096369350000900
Author(s):  
B. Lamy ◽  
E. Dixneuf
Keyword(s):  
Composite Materials ◽  
Damage Evolution ◽  
Damage Tolerance ◽  
Low Energy ◽  
Analytical Models ◽  
Woven Composites ◽  
Charpy Test ◽  
Damage Process ◽  
Flexural Tests ◽  
Damage Processes

Experiments were conducted in order to study damage process generated on particular composite materials by low energy impacts. Woven and knitted reinforcement- structures were tested using a Charpy test. Experimental laws and analytical models characterising the damage evolution in these composite materials subjected to successive impacts are proposed and compared. Damage processes are different in both composites. The rupture of the woven composites is controlled by crackings and delaminations, the latter does not occur in the knitted ones. These analyses emphasise the interest of using knitted reinforcements in composite materials.

scholarly journals Experimental Study of Plasma Plume Analysis of Long Pulse Laser Irradiates CFRP and GFRP Composite Materials

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 545
Author(s):  
Yao Ma ◽  
Chao Xin ◽  
Wei Zhang ◽  
Guangyong Jin
Keyword(s):  
Composite Materials ◽  
Laser Processing ◽  
Plasma Plume ◽  
Material Surface ◽  
Laser Fabrication ◽  
Breakdown Time ◽  
Reinforced Polymer ◽  
Gfrp Composite ◽  
Damage Process ◽  
Long Pulse

The application of laser fabrication of fiber-reinforced polymer (FRP) has an irreplaceable advantage. However, the effect of the plasma generated in laser fabrication on the damage process is rarely mentioned. In order to further study the law and mechanism of laser processing, the laser process was measured. CFRP and GFRP materials were damaged by a 1064 nm millisecond pulsed laser. Moreover, the propagation velocity and breakdown time of plasma plume were compared. The results show that GFRP is more vulnerable to breakdown than CFRP under the same conditions. In addition, the variation of plasma plume and material surface temperature with the number of pulses was also studied. The results show that the variation trend is correlated, that is, the singularities occur at the second pulse. Based on the analysis of experimental phenomena, this paper provides guidance for plasma phenomena in laser processing of composite materials.

scholarly journals Acoustic emission signatures prior to snow failure

2018 ◽  
Vol 64 (246) ◽  
pp. 543-554 ◽  
Author(s):  
ACHILLE CAPELLI ◽  
INGRID REIWEGER ◽  
JÜRG SCHWEIZER
Keyword(s):  
Loading Rate ◽  
Critical Phenomenon ◽  
Acoustic Emissions ◽  
Test Apparatus ◽  
Snow Layer ◽  
Loading Rates ◽  
Damage Process ◽  
Damage Processes ◽  
Increasing Load ◽  
Snow Samples

ABSTRACTSnow slab avalanches are caused by cracks forming and propagating in a weak snow layer below a cohesive slab. The gradual damage process leading to the formation of the initial failure within the weak layer (WL) is still not entirely understood. To this end, we designed a novel test apparatus that allows performing loading experiments with large snow samples (0.25 m2) including a WL at different loading rates and simultaneously monitoring the acoustic emissions (AE) response. By analyzing the AE generated by micro-cracking, we studied the evolution of the damage process preceding snow failure. At fast loading rates, the exponent of the AE energy distribution (b-value) gradually changed, and both the energy rate and the inverse waiting time increased exponentially with increasing load. These changes in AE signature indicate a transition from small to large events and an acceleration of the damage processes leading to brittle failure. For the experiments at slow loading rate, these changes in the AE signature were not or only partially present, even if the sample failed, indicating a different evolution of the damage process. The observed characteristics in AE response provide new insights on how to model snow failure as a critical phenomenon.

scholarly journals Research progress in damage evolution of woven composites

2020 ◽  
Vol 50 (7) ◽  
pp. 876-896
Author(s):  
Feng LIAO ◽  
Tao ZHENG ◽  
JinZhao HUANG ◽  
LiCheng GUO ◽  
JiuZhou ZHAO ◽  
...  
Keyword(s):  
Damage Evolution ◽  
Woven Composites ◽  
Research Progress

scholarly journals Damage detection in laminar thermoplastic composite materials by means of embedded optical fibers

2006 ◽  
Vol 60 (7-8) ◽  
pp. 176-179
Author(s):  
Aleksandar Kojovic ◽  
Irena Zivkovic ◽  
Ljiljana Brajovic ◽  
Dragan Mitrakovic ◽  
Radoslav Aleksic
Keyword(s):  
Composite Materials ◽  
Optical Fiber ◽  
Real Time ◽  
Optical Fibers ◽  
Impact Damage ◽  
Experimental Testing ◽  
Low Energy ◽  
Thermoplastic Composite ◽  
Woven Fabric ◽  
The Impact

This paper investigates the possibility of applying optical fibers as sensors for investigating low energy impact damage in laminar thermoplastic composite materials, in real time. Impact toughness testing by a Charpy impact pendulum with different loads was conducted in order to determine the method for comparative measurement of the resulting damage in the material. For that purpose intensity-based optical fibers were built in to specimens of composite materials with Kevlar 129 (the DuPont registered trade-mark for poly(p-phenylene terephthalamide)) woven fabric as reinforcement and thermoplastic PVB (poly(vinyl butyral)) as the matrix. In some specimens part of the layers of Kevlar was replaced with metal mesh (50% or 33% of the layers). Experimental testing was conducted in order to observe and analyze the response of the material under multiple low-energy impacts. Light from the light-emitting diode (LED) was launched to the embedded optical fiber and was propagated to the phototransistor-based photo detector. During each impact, the signal level, which is proportional to the light intensity in the optical fiber, drops and then slowly recovers. The obtained signals were analyzed to determine the appropriate method for real time damage monitoring. The major part of the damage occurs during impact. The damage reflects as a local, temporary release of strain in the optical fiber and an increase of the signal level. The obtained results show that intensity-based optical fibers could be used for measuring the damage in laminar thermoplastic composite materials. The acquired optical fiber signals depend on the type of material, but the same set of rules (relatively different, depending on the type of material) could be specified. Using real time measurement of the signal during impact and appropriate analysis enables quantitative evaluation of the impact damage in the material. Existing methods in most cases use just the intensity of the signal before and after the impact, as the measure of damage. This method could be used to monitor the damage in real time, giving warnings before fatal damage occurs.

The Use of Vibrothermography for Monitoring Damage Evolution in Composite Materials

1991 ◽  
pp. 424-432
Author(s):  
L. Schillemans ◽  
D. Van Hemelrijck ◽  
F. De Roey ◽  
I. Daerden ◽  
F. Boulpaep ◽  
...  
Keyword(s):  
Composite Materials ◽  
Damage Evolution

Damage detection of unidirectional carbon fiber–reinforced laminates with embedded magnetostrictive particulates: A preliminary study

2012 ◽  
Vol 24 (8) ◽  
pp. 991-1006 ◽  
Author(s):  
Oliver J Myers ◽  
George Currie ◽  
Jonathan Rudd ◽  
Dustin Spayde ◽  
Nydeia Wright Bolden
Keyword(s):  
Composite Materials ◽  
Carbon Fiber ◽  
Nondestructive Evaluation ◽  
Composite Laminates ◽  
Composite Structures ◽  
Single Layer ◽  
Polymeric Composite ◽  
Analytical Models ◽  
Fiber Reinforced ◽  
Carbon Fiber Reinforced

Defects in composite laminates are difficult to detect because of the conductive and paramagnetic properties of composite materials. Timely detection of defects in composite laminates can improve reliability. This research illustrates the preliminary analysis and detection of delaminations in carbon fiber laminate beams using a single layer of magnetostrictive particles and noncontacting concentric magnetic excitation and sensing coils. The baseline analytical models also begin to address the intrusive nature of the magnetostrictive particles as well as relate the applied excitation field with the stress and magnetic flux densities induced in the magnetostrictive layer. Numerical methods are used to begin to characterize the presence of magnetostrictive particles in the laminate and the behavior of the magnetostrictive particles in relationship to the magnetic field used during sensing. Unidirectional laminates with embedded delaminations are used for simulations and experimentations. A novel, yet simplified fabrication method is discussed to ensure consistent scanning and sensing capabilities. The nondestructive evaluation scanning experiments were conducted with various shapes and sizes of damages introduced into carbon fiber–reinforced polymeric composite structures. The results demonstrate high potential for magnetostrictive particles as a low-cost, noncontacting, and reliable sensor for nondestructive evaluation of composite materials.

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