Effect of transverse reinforcement on cracking of CFRP composite laminates under static and fatigue loads

2020 ◽  
Vol 54 (25) ◽  
pp. 3755-3766 ◽  
Author(s):  
Maciej Giżyński
Keyword(s):  
Composite Laminates ◽  
Crack Density ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Transverse Reinforcement ◽  
Damage Growth ◽  
Cfrp Laminates ◽  
Cfrp Composite ◽  
Static Tensile

Several CFRP laminates with various layups, possessing two distinctive forms of transverse reinforcement either UD 90° or fabric 0°/90°, were tested in both static and fatigue tests. All examined layups were considered to be used in the wingbox design of the multipurpose turboprop aircraft. In-situ microscopic observations were carried out during the tests. Static tensile tests allowed to find the strength of the laminas, stress, and strains at which cracks started to propagate, crack density during the test. The microscopic observations allowed to establish cracks’ growth paths. The first crack in laminates having fabric 0°/90° laminas usually was observed for higher stress and strain than in laminates with UD 90° laminas. Also, the later ones showed a tendency to significantly delaminate along the interface between UD 90° and UD 45° laminas. The fatigue test was carried out in order to find how to distinguish damage growth in both families of laminates that affects their fatigue life. As an outcome, S-N lines were determined. During the test the microscopic observations were made, which allowed to show crack and delamination growth during successive load cycles. The microscopic observations showed that cyclic loading leads to the fast growth of delaminations at the interface of fabric 0°/90°ply or UD 90° laminas.

scholarly journals Investigations on arc brazing for galvanized heavy steel plates in steel and shipbuilding

2021 ◽  
Author(s):  
Philipp Andreazza ◽  
Andreas Gericke ◽  
Knuth-Michael Henkel
Keyword(s):  
Low Cost ◽  
Thin Sheet ◽  
Steel Structures ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Steel Plates ◽  
Galvanized Steel ◽  
Filler Materials ◽  
Static Tensile ◽  
Brazed Joints

AbstractArc brazing with low-melting copper-based filler materials, which has long been established and standardized in the thin sheet sector, offers numerous advantages in the processing of predominantly electrolytically galvanized steel structures. In steel and shipbuilding, on the other hand, equipment parts made of thick steel sheets are hot-dip galvanized at low cost and with good corrosion-inhibiting properties. Quality welding of such constructions is not possible without special precautions such as removing the zinc layer and subsequent recoating. With regard to greater plate thicknesses, arc brazing was analyzed in these investigations as an alternative joining method with regard to its suitability for practical use. Within the scope of the investigations, CuSi3Mn, CuMn12Ni2, and four different aluminum bronzes were examined on different sheet surface conditions with regard to the geometrical and production parameters. This was carried out by build-up and connection brazing, executed as butt and cross joints. Quasi-static tensile tests and fatigue tests were used to assess the strength behavior. In addition, metallographic analyses are carried out as well as hardness tests. The suitability for multi-layer brazing and the tendency to distortion were also investigated, as well as the behavior of arc brazed joints under corrosive conditions.

Mechanical Properties of Flat Braided Composites With a Circular Hole

1999 ◽  
Author(s):  
Takeru Ohki ◽  
Shinya Ikegaki ◽  
Ken Kurasiki ◽  
Hiroyuki Hamada ◽  
Masaharu Iwamoto
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Circular Hole ◽  
Fracture Behavior ◽  
Fatigue Property ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Braided Composites ◽  
Static Tensile ◽  
The One

Abstract In this study, fracture behavior and strength in the flat braided bar with a circular hole were investigated by static and fatigue test. Two type of specimens were prepared. They are a braided flat bar with an integrally-formed braided hole and a braided flat bar with a machined hole. Moreover, we also examined a specimen that had a metal pin inserted at the circular hole. This specimen was subjected to a static tensile test. The results of the tensile tests indicate that the strength of the flat bar with a braided hole was larger than that of the one with the machined hole. Furthermore, from the results of the fatigue tests, the flat bar with the braided hole showed higher fatigue property than that of the one with the machined hole.

NUMERICAL PREDICTION OF STIFFNESS DEGRADATION OF THIN-PLY CFRP LAMINATES UNDER FATIGUE LOADING

2021 ◽  
Author(s):  
RYOMA AOKI ◽  
RYO HIGUCHI ◽  
TOMOHIRO YOKOZEKI
Keyword(s):  
Composite Laminates ◽  
Damage Mechanics ◽  
Crack Density ◽  
Continuum Damage Mechanics ◽  
Fatigue Loading ◽  
Stiffness Degradation ◽  
Cfrp Laminates ◽  
Mechanics Model ◽  
Element Simulation ◽  
Proposed Model

This study aims to conduct a fatigue simulation for predicting the stiffness degradation of thin-ply composite laminates with several ply thicknesses. For the simulation, a fatigue evolution model of intra-laminar damage in thin-ply composite laminates considering the effect of ply thickness was proposed. The intra-laminar damage evolution was modeled using the continuum damage mechanics model and the static and fatigue evolution law were formulated by relating the transverse crack density to the damage variable. The finite element simulation using the proposed model was conducted to predict the stiffness degradation of the laminates as a function of the number of loading cycles. The simulation results show that the experimental data can be reproduced by using the proposed fatigue model.

Mechanical Properties of Flat Braided Composites With a Circular Hole

2000 ◽  
Vol 122 (4) ◽  
pp. 420-424 ◽  
Author(s):  
Takeru Ohki ◽  
Shinya Ikegaki ◽  
Ken Kurasiki ◽  
Hiroyuki Hamada ◽  
Masaharu Iwamoto
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Circular Hole ◽  
Fracture Behavior ◽  
Fatigue Property ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Braided Composites ◽  
Static Tensile ◽  
The One

In this study, fracture behavior and strength in the flat braided bar with a circular hole were investigated by static and fatigue test. Two types of specimen were prepared. They are a braided flat bar with an integrally formed braided hole and a braided flat bar with a machined hole. Moreover, we also examined a specimen that had a metal pin inserted at the circular hole. This specimen was subjected to a static tensile test. The results of the tensile tests indicate that the strength of the flat bar with a braided hole was larger than that of the one with the machined hole. Furthermore, from the results of the fatigue tests, the flat bar with the braided hole showed higher fatigue property than that of the one with the machined hole. [S0094-4289(00)02604-9]

scholarly journals In Situ and Post-Mortem Characterizations of Ultrasonic Spot Welded AZ31B and Coated Dual Phase 590 Steel Joints

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 899 ◽  
Author(s):  
Jian Chen ◽  
Yong Chae Lim ◽  
Donovan Leonard ◽  
Hui Huang ◽  
Zhili Feng ◽  
...  
Keyword(s):  
High Speed ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Image Correlation ◽  
Joint Interface ◽  
Welding Time ◽  
Cross Sectional ◽  
Welding Condition ◽  
Lap Shear

Ultrasonic spot welding using different welding conditions was applied to join dissimilar metals of galvanized DP590 steel and AZ31B magnesium sheets. In situ high-speed imaging, digital image correlation, and infrared thermography were utilized to quantitatively study the interfacial relative motion, surface indentation, and heat generation across the joint faying interface and the sheet/sonotrode interfaces under the welding condition of moderate welding power and short welding time. For welds made with high power and long welding time, lap shear tensile tests as well as fatigue tests were carried out. Different fracture modes were observed after the lap shear tensile tests and fatigue tests performed under different peak loads. Post-weld cross-sectional analysis with scanning electron microscopy coupled with energy dispersive X-Ray spectroscopy revealed the variation of morphology and chemical composition at the joint interface for welds made with different welding conditions.

Fatigue Response of Hybrid Ti/APC-2 Nanocomposite Laminates with Single-Edged Cracks

2013 ◽  
Vol 592-593 ◽  
pp. 425-428
Author(s):  
Ming Hwa R. Jen ◽  
Che Kai Chang ◽  
Bo Cyuan Lin
Keyword(s):  
Mechanical Properties ◽  
Crack Length ◽  
Composite Laminates ◽  
Residual Life ◽  
Tensile Tests ◽  
Cyclic Tests ◽  
Paris Law ◽  
Modified Method ◽  
Longitudinal Stiffness ◽  
Static Tensile

The aims of this study are to fabricate Ti/APC-2 hybrid composite laminates with and without (W/WO) nanoparticles and investigate the mechanical properties of laminates with single-edged cracks due to both tensile and cyclic tests. The mechanical properties such as ultimate tensile strength and longitudinal stiffness of original composite laminates W/WO nanoparticles were first obtained from the static tensile tests. However, the load-displacement diagrams were plotted for the crack laminates. The constant stress amplitude tension-tension cyclic tests were conducted to receive the S-N curves and fatigue data. The ultimate strengths for both Ti/APC-2 composite laminates W/WO nanoparticles were very close at varied crack length. Ti/APC-2 cross-ply nanocomposite laminates had better fatigue resistance than that of laminates without nanoparticles. The longer the crack length is, the more their properties are reduced. Also, the values of fracture toughness of both hybrid cracked laminates W/WO nanoparticles were obtained by rule of mixtures and found acceptable. Finally, in predicting crack growth rate and residual life, instead of commonly used Paris Law for metals, the modified method was adopted for hybrid cracked laminates. The prediction is not satisfactorily acceptable, even if most results are in good agreement with empirical data.

Tensile and Fatigue Testings of Hybrid Al/APC-2 Nanocomposite Laminates at Elevated Temperature

2008 ◽  
Vol 47-50 ◽  
pp. 592-595 ◽  
Author(s):  
Ming Hwa R. Jen ◽  
Yi Chun Sung ◽  
Yin Da Lai
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperature ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Thermoplastic Matrix ◽  
Longitudinal Stiffness ◽  
Hybrid Laminates ◽  
Static Tensile ◽  
Aluminum Alloy 2024 ◽  
Strength And Stiffness

To deal with the stringent operational demands the aerospace structural materials of light weight Aluminum alloy 2024 sheets and plies of carbon fibers reinforced thermoplastic matrix PEEK were used to sustain at least 80% of their mechanical properties at elevated temperature. The addition of nanoparticles SiO2 can enhance the composite laminate strength and stiffness. Also, Al 2024 sheets were treated by an anodic method of electroplating to increase surface roughness to achieve perfectly bonding with matrix PEEK. Then, the modified diaphragm curing process was adopted to make the innovative hybrid Al/APC-2 hybrid nanocomposite laminates. Next, both static tensile and fatigue tests were conducted at elevated temperature to obtain the mechanical properties, lives and failure mechanisms to verify the improved features of hybrid specimens. From tensile tests the mechanical properties of Al/APC-2 [4Al/0/±45/90/2Al]s hybrid laminates at elevated temperature were obtained. Although there is a big drop at 150°C, the reduction in strength from RT to 125°C is generally not significant. The longitudinal stiffness is almost unchanged at elevated temperature. After cyclic tension-tension (T-T) tests, the positions of received S-N curves go downwards as temperature rising. No delaminations were found in both tests. If the applied stress normalized by the ultimate strength at corresponding temperature, the normalized S-N curves are closer with some curve positions reversed. Significant improvement of manufacturing and enhancement of mechanical properties in hybrid laminates were achieved finally.

A Two Dimensional Phenomenological Model for Damage of Arteries

2007 ◽  
Author(s):  
Alexander Rachev
Keyword(s):  
Mechanical Strength ◽  
Vascular Tissue ◽  
Longitudinal Direction ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Traumatic Rupture ◽  
Artery Graft ◽  
Arterial Tissue ◽  
Static Tensile ◽  
Failure Properties

Loss of mechanical strength of arteries can manifest itself in many ways including rupture of a vulnerable atherosclerotic plaques, burst of saccular aneurisms, rupture of artery/graft anastomosis, and traumatic rupture of aorta by impact loading due to automobile accidents. In all cases the fracture of the tissue leads to sudden cardiovascular events that often have a lethal end. To date there are insufficient experimental data on the mechanical strength of healthy and diseased vascular tissue. Most of the results refer to the failure properties from uniaxial quasi-static tensile tests on strips and rings. It was found that the tensile strength is different in the circumferential and longitudinal direction especially when it is determined from strain controlled dynamic tests [1]. Results form load-controlled fatigue tests have shown a gradual softening of the arterial tissue, development of a residual (plastic) deformation, and existence of S-N curve [2]. However, the information from uniaxial tests is not sufficient to predict the damage of tubular segments due to coupling between circumferential and longitudinal stress via constitutive equations and deformed geometry. Moreover, the mechanisms of arterial tissue failure remain unknown.

The role of electrical anisotropy and effective conducting thickness in understanding and interpreting static resistance measurements in CFRP composite laminates

2019 ◽  
Vol 54 (7) ◽  
pp. 867-882
Author(s):  
Robert J Hart ◽  
OI Zhupanska
Keyword(s):  
Composite Laminates ◽  
Electrical Response ◽  
Current Source ◽  
Electrical Characterization ◽  
Probe Method ◽  
Electrical Anisotropy ◽  
Cfrp Laminates ◽  
Electrical Resistivities ◽  
Cfrp Composite ◽  
Point Type

This study is focused on (i) the experimental characterization of the anisotropic electrical resistivity of carbon fiber reinforced polymer (CFRP) composites and (ii) the development and experimental validation of predictive finite element (FE) models of the electrical response in CFRP laminates based on the concept of the effective conducting thickness. Two experimental methods have been developed to characterize the anisotropic electrical resistivities in three principle directions for the CFRP composite laminates using a direct current source. One method utilizes a traditional 6-probe resistance scheme and the alternative point-type 4-probe method is based on a handheld probe device similar to the JIS K7194 standard for homogenous plastics. An extensive experimental study has been conducted to characterize the anisotropic electrical resistivities of 16-ply unidirectional and 16-ply symmetric cross-ply IM7/977-2 and 32-ply unidirectional IM7/977-3 composites using the developed methods. Exploiting the concept of the effective conducting thickness, which describes the effective depth of current penetration through the thickness of an electrically anisotropic material, a unique methodology is developed for constructing FE models of these highly anisotropic CFRP materials. The concept of effective conducting thickness was identified as a critical component in achieving accuracy of the FE results as well as recovery of experimental resistivity from the alternative point-type 4-probe method. The FE models have been validated using the experimental results on the CFRP specimens of varying layup and thickness, and the techniques developed in this work may lead to advancements in non-destructive techniques in the areas of electrical characterization and damage sensing.

Influence of Ultrasonic Shear Wave on Defect Angles of Stacking Using CFRP Composite Laminates

2006 ◽  
Vol 306-308 ◽  
pp. 787-792
Author(s):  
Je Woong Park ◽  
Sun Kyu Kim ◽  
Young Nam Kim ◽  
In Young Yang ◽  
David K. Hsu ◽  
...  
Keyword(s):  
Shear Wave ◽  
Composite Laminates ◽  
Azimuthal Angle ◽  
Normal Incidence ◽  
Cfrp Laminates ◽  
Fiber Placement ◽  
Decomposition Model ◽  
Vector Decomposition ◽  
Optical Test ◽  
Cfrp Composite

Because the layup of composite laminates influences there properties, the strength of composites depends on layup sequence of CFRP laminates. It is very important to detect ply error before the laminate is cured for both manual procedure and fiber placement procedure. An ultrasonic technique would be very beneficial, which could be used to test the part after and before curing laminates and requires less time than the optical test. Scanners were set out for different measurement modalities for acquiring ultrasonic signals as a function of in-plane azimuthal angle. The first motorized scanner was utilized for making transmission measurements using a pair of normal-incidence shear wave transducers. A scanner was built for the acousto-ultrasonic configuration using contact transducers. And a ply-by-ply vector decomposition model has been utilized for evaluating layup errors in composite laminates fabricated from unidirectional plies. We have compared the test results with model data. It is found that high probability shows between experimentations and the decomposition model in characterizing cured and uncured laminates with defect angles.

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