Static and Fatigue Failure Response of Woven Carbon Fiber Specimens with Double Edge Notches

Amini, Ahmad J

doi:10.15368/theses.2010.188

Cited by 3 publications

(3 citation statements)

References 4 publications

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“…Once the strain gages were mounted and ample time was allowed for the bonding agent to dry, Instructions on how to use the versa channel option were followed from Amini's master's thesis [28]. The test was run on four coupons, which were loaded to a maximum of 3000-lbf to avoid failure.…”

Section: Carbon Fiber Face Sheets (Acg Ltm45el/cf1803)mentioning

confidence: 99%

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The Effect of a Low-Velocity Impact on the Flexural Strength and Dynamic Response of Composite Sandwiches with Damage Arrestment Devices

Rider¹

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The Effect of a Low-Velocity Impact on the Flexural Strength and Dynamic Response of Composite Sandwiches with Damage Arrestment Devices By: Kodi A. Rider Impact strength is one of the most important structural properties for a designer to consider, but is often the most difficult to quantify or measure. A constant concern in the field of composites is the effect of foreign object impact damage because it is often undetectable by visual inspection. An impact can create interlaminar damage that often results in severe reductions in strength and instability of the structure. The main objective of this study is to determine the effectiveness of a damage arrestment device (DAD) on the mechanical behavior of composite sandwiches, following a low-velocity impact. A 7.56-lbf crosshead dropped from a height of 37.5-inches was considered for the low-velocity impact testing. In this study, the experimental and numerical analysis of composite sandwiches were investigated, which included static 4point bend and vibration testing. Composite sandwiches were constructed utilizing four-plies of Advanced Composites Group LTM45EL/CF1803 bi-directional woven carbon fiber face sheets with a General Plastics Last-A-Foam FR-6710 rigid polyurethane core. Specimens were cured in an autoclave, using the manufacturer's specified curing cycle. In addition to the experimental and numerical analysis of composite sandwiches, developing and building a data acquisition (DAQ) system for the Dynatup 8250 drop weight impact tester was accomplished. Utilizing National Instruments signal conditioning hardware, in conjunction with LabView and MATLAB, complete testing software was developed and built to provide full data acquisition for an impact test. The testing hardware and software provide complete force vs. time history and crosshead acceleration of the impact event, as well as provide instantaneous impact velocity of the projectile. The testing hardware, software, and procedures were developed and built in the Aerospace Structures/Composites laboratory at Cal Poly for approximately 15% of the cost from the manufacturer. In the first study, static 4-point bend testing was investigated to determine the residual flexural strength of composite sandwich beams following a low-velocity impact. Four different specimen cases were investigated in the 4-point bend test, with and without being impacted: first a control beam with no

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Section: Carbon Fiber Face Sheets (Acg Ltm45el/cf1803)mentioning

confidence: 99%

“…28. Time-domain decay response of the 1st bending mode for the control plate with no DAD key or initial delamination.…”

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confidence: 99%

The Effect of a Low-Velocity Impact on the Flexural Strength and Dynamic Response of Composite Sandwiches with Damage Arrestment Devices

Rider¹

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“…30 The curing methods that were tested included the "green" control case, the 220°F thermo-treatment, the 3%, 6%, and 9% salt 220°F thermo-treatment, the lime 220°F thermo-treatment, the oil 220°F thermo-treatment, and the 3% salt 220°F thermo-treatment loaded in the direction perpendicular to the fibers. To determine an average strain for each testing group, ten coupons are tested.…”

Section: Poisson's Ratiomentioning

confidence: 99%

Mechanical Optimization and Buckling Analysis of Bio-Composites

Chan¹

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Mechanical Optimization and Buckling Analysis of Bio-compositesBy: Cameron D. Chan Today's environmental concerns have led a renewed search in industry to find new sustainable materials to replace non-renewable resources. President Barack Obama also quoted in the recent 2012 Presidential Debate "that there is a need to build the energy sources of the future and invest in solar, wind, and bio-fuels." Bio-composites are believed to be the future and the new substitute for non-renewable resources. Bio-composites are similar to composites in that they are made up of two constituent materials; however the main difference is that biocomposites are made from natural fibers and a biopolymer matrix. This research investigates the buckling behavior of bamboo and will analyze and determine the slender ratio that will induce buckling when bamboo is used as a column. Along with the investigation of the bamboo under buckling, this study will also show the potential of bio-composites to replace nonrenewable resources in industry through experimental and numerical analysis. However, in order to study the buckling behavior of the bamboo, the mechanical characteristics of the bamboo and optimal curing treatment first had to be established. This is because, in order for bamboo to acquire proper strength characteristics, the bamboo must first be treated.Due to the scarcity of bamboo material in the lab, the obtainment of the mechanical properties of the bamboo as well as the optimal curing treatment was done in collaboration with Jay Lopez. In order for bamboo to acquire proper strength characteristics, the bamboo must be treated. In the first study, a total of four different types of natural treatments were analyzed to optimize the mechanical characteristics of bamboo. To assess each curing method, tensile and compression tests were performed to obtain the mechanical properties. Due to each bamboo culm having different thicknesses and cross sections, the specific strength property is used to normalize the data and allow for easy comparison and assessing of each curing method equally. The specific strength parameter is defined as the ultimate stress divided by the density of the material. These curing treatments consisted of four thermo-treatments, three different percentages of salt treatments, one lime treatment, and one oil treatment. The thermotreatments consisted of heating the bamboo internodes in an autoclave with no pressure at 150 o F, 180°F, 200°F, and 220°F. The experimental results of the thermo-treatments determined that bamboo obtains higher mechanical properties as well as reduced weight when heated at higher temperatures. This is explained by the increasing bound water extracted from the bamboo material at higher temperatures. In addition to finding the optimal heat treatment, the internodes of bamboo were soaked in natural additives that included a 3%, 6%, and 9% Instant Ocean sea salt solution, a Bonide hydrated lime solution, and a Kirkland canola oil solution for approximately five days and then heat tr...

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The Effect of Sensor Mass, Sensor Location, and Delamination Location of Different Composite Structures Under Dynamic Loading

Liu¹

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This study investigated the effect of sensor mass, sensor location, and delamination location of different composite structures under dynamic loading. The study pertains to research of the use of accelerometers and dynamic response as a cost-effective and reliable method of structural health monitoring in composite structures. The composite structures in this research included carbon fiber plates, carbon fiberfoam sandwich panels, and carbon-fiber honeycomb sandwich panels. The composite structures were manufactured with the use of a Tetrahedron MTP-8 heat press. All work was conducted in the Cal Poly Aerospace Structures/Composites Laboratory. Initial delaminations were placed at several locations along the specimen, including the bending mode node line locations. The free vibration of the composite structure was forced through a harmonic horizontal vibration test using an Unholtz-Dickie shake system. A sinusoidal sweep input was considered for the test. The dynamic response of the composite test specimens were measured using piezoelectric accelerometers. Measurements were taken along horizontal and vertical locations on the surfaces of the composite structures. Square inch grids were marked on the surfaces to create a meshed grid system. Accelerometer measurements were taken at the center of the grids. The VIP Sensors 1011A piezoelectric accelerometer was used to measure vibration response. The measurements were then compared to response measurements taken from a PCB Piezotronics 353B04 single access accelerometer to determine the effects of sensor mass. Deviations in bending mode natural frequency and differences in mode shape amplitude became the criteria for evaluating the effect of sensor mass, sensor location, and delamination location. Changes in damping of the time response were also studied. The experimental results were compared to numerical models created using a finite element method. The experimental results and numerical values were shown to be in good agreement. The sensor mass greatly affected the accuracy and precision of vibration response measurements in the composites structures. The smaller weight and area of the VIP accelerometer helped to minimize the decrease in accuracy and precision due to sensor mass. The effect of sensor location was found to be coupled with the effect of sensor mass and v the bending mode shape. The sensor location did not affect the vibration response measurements when the sensor mass was minimized. Off-center horizontal sensor placement showed the possibility of measuring vibration torsion modes. The effect of delamination changed the bending mode shape of the composite structure, which corresponded to a change in natural frequency. The greatest effect of the delamination was seen at the bending mode node lines, where the bending mode shape was most significantly affected. The effect of delamination was also dependent on the location of the delamination and the composite structure type. The results of this study provided considerations for future research of an act...

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Static and Fatigue Failure Response of Woven Carbon Fiber Specimens with Double Edge Notches

Cited by 3 publications

References 4 publications

The Effect of a Low-Velocity Impact on the Flexural Strength and Dynamic Response of Composite Sandwiches with Damage Arrestment Devices

The Effect of a Low-Velocity Impact on the Flexural Strength and Dynamic Response of Composite Sandwiches with Damage Arrestment Devices

Mechanical Optimization and Buckling Analysis of Bio-Composites

The Effect of Sensor Mass, Sensor Location, and Delamination Location of Different Composite Structures Under Dynamic Loading

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