Development of Novel Compact Compression Specimen for Matrix Compression Damage Initiation and Propagation Behavior in Fiber Reinforced Composites

2018 ◽  
Author(s):  
Tim A. McKinley ◽  
Kevin T. Carpenter ◽  
John P. Parmigiani
Keyword(s):  
High Performance ◽  
Tensile Failure ◽  
Fiber Reinforced Polymers ◽  
Fiber Reinforced ◽  
Damage Initiation ◽  
Propagation Behavior ◽  
Matrix Compression ◽  
The Matrix ◽  
Compression Damage

Robust design and analysis of carbon fiber reinforced polymers (CFRP) mandates a thorough understanding of the onset and propagation of damaging mechanisms. Damage can manifest from fiber tension, fiber compression, matrix tension, and matrix compression. Of these damage forms, matrix compression has seen the least attention. Previous work has developed experimental specimens that enabled characterization of the onset and propagation of matrix compression damage. However, if high performance composite materials are used complications can arise when the matrix compression strength (σMC) exceeds the matrix tension strength (σMT). When the σMC/σMT ratio is greater than 2, compact compression (CC) specimens can exhibit matrix tension damage before the onset of matrix compression damage. The onset of matrix tension damage prevents proper characterization of matrix compression damage mechanisms. This paper presents the development of a novel stepped compact compression specimen. The reduced thickness of the stepped region allows significant matrix-compression damage to occur prior to tensile failure. Specimens comprised of 90° plies were fabricated using either a machined taper or a layering process. Both methods were successful however variability in machining generated substantial inconsistency and layering was found to be superior.

Experimental Specimen for Classification of Matrix Compression Damage in Carbon Fiber Reinforced Polymers

2018 ◽  
Author(s):  
Taylor J. Rawlings ◽  
Kevin T. Carpenter ◽  
John P. Parmigiani
Keyword(s):  
Carbon Fiber ◽  
Crack Propagation ◽  
Visible Region ◽  
Material Model ◽  
Image Correlation ◽  
Fiber Reinforced Polymers ◽  
Fiber Reinforced ◽  
Matrix Compression ◽  
Carbon Fiber Reinforced ◽  
Compression Damage

Composite materials are becoming increasingly common in the aerospace industry. In order for simulation and modeling to accurately predict failure of composites, a material model based on observed damage mechanisms is required. Composites are commonly classified into four damage categories based on the composite constituents and their loading condition: fiber tension, fiber compression, matrix tension, and matrix compression. Previous work identified a compact compression (CC) specimen as a suitable option for isolating matrix compression damage. However upon continued testing, stable crack propagation in the specimen was limited to a relatively low material failure ratio (σCompressive/σTension). This paper presents specimen geometry that can isolate matrix compression damage in materials with a failure ratio greater than two, the limit of the compact compression specimens. Initial specimen selection used the compact compression specimens from previous research and added additional specimens based on commonly used compressions specimens for different materials. The added specimens included center notched compression (CNC), edge notch compression (ENC), and four-point bending (4PB). All specimens were evaluated experimentally with the success criteria of controlled propagation of a matrix compression crack. In addition to propagating a controlled matrix compression crack, specimens were required to have a visible region around the stress concentrator to allow for digital image correlation (DIC) image capture during the experiments. The specimens were manufactured from a carbon fiber reinforced polymer (CFRP) with a failure ratio greater than six. CC and 4PB specimens were unable to produce a compression crack before any other failure methods were present. CNC specimens produced an unstable compression crack that progressed from the notch to the edge of the specimen too rapidly to acquire meaningful crack propagation data. ENC specimens showed some ability to stably propagate a crack, however some tests resulted in an unstable crack propagation similar to the CNC specimens. In order to increase the test repeatability, a tapered thickness was added to the specimen around the notch tip. The resulting tapered ENC (TENC) produced repeatable controlled matrix compression crack propagation. Ultimately, the specimen fails when the crack has propagated through the entire width of the specimen. TENC specimens show promise for isolating matrix compression damage in materials with high failure ratios. Continued testing of CFRP with TENC specimens could be used to refine the material model for finite element analysis.

TEM characterization of reaction zone in a SiC fiber-reinforced titanium alloy

1988 ◽  
Vol 46 ◽  
pp. 738-739
Author(s):  
G. Das ◽  
R. E. Omlor
Keyword(s):  
Titanium Alloys ◽  
Reaction Zone ◽  
Carbon Layer ◽  
Fiber Reinforced ◽  
Reaction Products ◽  
Sic Fibers ◽  
Sic Fiber ◽  
The Matrix ◽  
Immense Potential

Fiber reinforced titanium alloys hold immense potential for applications in the aerospace industry. However, chemical reaction between the fibers and the titanium alloys at fabrication temperatures leads to the formation of brittle reaction products which limits their development. In the present study, coated SiC fibers have been used to evaluate the effects of surface coating on the reaction zone in the SiC/IMI829 system.IMI829 (Ti-5.5A1-3.5Sn-3.0Zr-0.3Mo-1Nb-0.3Si), a near alpha alloy, in the form of PREP powder (-35 mesh), was used a茸 the matrix. CVD grown AVCO SCS-6 SiC fibers were used as discontinuous reinforcements. These fibers of 142μm diameter contained an overlayer with high Si/C ratio on top of an amorphous carbon layer, the thickness of the coating being ∽ 1μm. SCS-6 fibers, broken into ∽ 2mm lengths, were mixed with IMI829 powder (representing < 0.1vol%) and the mixture was consolidated by HIP'ing at 871°C/0. 28GPa/4h.

Behaviour of Uniaxial Reinforced Concrete Columns Strengthened with Ultra-High Performance Concrete and Fiber Reinforced Polymers

2021 ◽  
Vol 28 (2) ◽  
pp. 54-72
Author(s):  
Abd-al-Salam Al-Hazragi ◽  
Assim Lateef
Keyword(s):  
Reinforced Concrete ◽  
High Performance ◽  
High Performance Concrete ◽  
Concrete Columns ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced Polymers ◽  
Tension Zone ◽  
Fiber Reinforced ◽  
Group A ◽  
Group B

This article investigates the behaviour of strengthened concrete columns using jacketing ultra-high-performance fiber reinforced concrete (UHPFRC) and carbon fiber-reinforced polymer (CFRP) under uniaxial loaded. The jacket was connected to the column core using shear connectors and (CFRP) fixed as a strip on the tension zone between the column cores and the jacketing. Seven column samples of square cross-section (120 x120) mm at the midsection with overall length of 1250 mm were cast using normal strength concrete (NSC) and having similar longitudinal and transverse reinforcement. The samples were made and tested under axial load at eccentricity equal to 120 mm up to failure. Test parameters were the thickness of jackets (25 and 35) mm and the width of CFRP (0,8, and 12) cm. Column specimens were tested, one of them was reference without any strengthening, and the other specimens divided into two groups (A, and B), and each group included three specimens based on the parameters. Group (A) has UHPFRC jacket thickness 25 mm and CFRP width (0,8, and 12) cm respectively, and group (B) has UHPFRC jacket thickness 35 mm and CFRP width (0,8, and 12) cm respectively. The outcomes of the article show that increasing the thickness of jacket, and width of CFRP lead to increase in the load carrying capacity about (110.5%,168.4%, and 184.2%) for group A, and (157.9%,226.3%, and 263.2%) for group B compared with the reference column due to delay in the appearance of cracks and their distribution. The mid-height lateral displacement of columns was decreased about (66.6%,42.3%, and 35.9%) for group A, and (46.15%,38.46%, and 32.3%) for group B, also the axial deformation of specimens decreased about (71.7%,60.86%, and 55.86%) for group A, and (65.5%,60.5%, and 53.4) for group B compared with the reference column. The ductility of columns that were strengthened with UHPFRC jacket only was increased about (13.67%,19.66%) for thickness(25,35) mm respectively, because of that UHPFRC jacket was contented on steel fibers, and the percentage decrease of ductility was about (5.1%,and 12%) for group (A), (1%,and 9.4%) for group (B) when bonded CFRP in the tension zone with width (8 ,and 12) cm respectively. The results show improvement in the initial and secant stiffness when, increased the thickness of jacket, and width of CFRP because of increase in the size of columns and improvement in the modulus of elasticity. The toughness increase was about (273.97%,301.55%, and 304.5%) for group A, and (453.69%,511.93%, and 524.28%) for group B compared with the reference column because of increase in the size of specimens and delay the appearance of cracks.

scholarly journals Effects of Defects on Bond Behavior of Fiber Reinforced Cementitious Matrix Materials

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 164 ◽  
Author(s):  
Antonio Bilotta ◽  
Gian Piero Lignola
Keyword(s):  
High Strength ◽  
Epoxy Adhesive ◽  
Fiber Reinforced ◽  
Bond Behavior ◽  
The Matrix ◽  
Low Sensitivity ◽  
Strengthening Technique ◽  
Geometrical Defects ◽  
Bond Tests

High-strength fibers embedded in inorganic matrix i.e., Fiber Reinforced Cementitious Mortar materials (FRCM) are commonly used as strengthening technique for existing masonry structures, due to the low sensitivity to debonding phenomena between substrate and matrix. Nevertheless, the use of lime or cement-based matrix instead of epoxy adhesive implies that attention has to be paid to the bond behavior between the fibers and the matrix, since sliding phenomena and cohesive failures in the mortar matrix can occur. The paper aims to investigate the effect of the mechanical properties of fiber and matrix on the FRCM efficiency, and potential geometrical defects, typical of real applications. The aim is to analyze the mechanical behavior of the FRCM system by simulating hypothetical bond tests, as they are usually performed in laboratories. The bond test has a significant role, as it is used for the qualification of the material, providing sometimes very scattered results. Hence, it is particularly important and greatly discussed in the scientific community and among manufactures and practitioners. The purpose is to understand where this variability could derive from and possibly how to contain it, to improve the characterization of FRCM systems. A mechanical model has been proposed to simulate the usual bond test to focus and stress the way in which each fiber slips out of the matrix as the load increases; and this has been recognized as the main reason for scattered results in bond tests. The model was then applied to the typical cases of PBO-FRCM and Glass-FRCM, hence considering different ratios for the fiber and matrix properties.

scholarly journals Characterization of fiber matrix interface of continuous‐discontinuous fiber reinforced polymers on the microscale

PAMM ◽  
2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Benedikt Rohrmüller ◽  
Michael Schober ◽  
Kerstin Dittmann ◽  
Peter Gumbsch ◽  
Jörg Hohe
Keyword(s):  
Fiber Reinforced Polymers ◽  
Matrix Interface ◽  
Fiber Reinforced ◽  
Reinforced Polymers ◽  
Discontinuous Fiber ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

Guidelines and Limitations of the Compact Compression Specimen

2019 ◽  
Author(s):  
David J. Plechaty ◽  
Kevin T. Carpenter ◽  
John P. Parmigiani
Keyword(s):  
Carbon Fiber ◽  
Test Specimen ◽  
Loading Rate ◽  
Material Models ◽  
Damage Initiation ◽  
Matrix Compression ◽  
Initiation And Propagation ◽  
Back Edge ◽  
Notch Length ◽  
Compression Damage

Abstract Damage initiation and propagation material models for carbon fiber composites can be categorized according to the loading applied to constituent components. An example of such categorization is fiber tension, fiber compression, matrix tension, and matrix compression material models. Of these, matrix compression has been by far the least studied based on amount of published literature. Recent work at Oregon State University (OSU) has begun to address this lack of study. OSU researchers have published several papers culminating in the specification of an effective test specimen for isolating matrix compression damage initiation and propagation in carbon fiber laminates. While providing compelling results indicating the effectiveness and usefulness of this test specimen, little or no information has been provided regarding its manufacture, usable notch lengths, and optimum loading rate during testing. Experience at OSU has shown that this information is critical and not trivial to obtain. The purpose of this paper is to provide specific guidelines and “lessons learned” needed for other researchers to efficiently and effectively use this specimen in a comprehensive study. Test specimens are manufactured in the OSU Composites Materials Manufacturing Laboratory using typical commercial pre-peg carbon fiber following the specified layup and curing procedures. Once the material was cured the carbon fiber plate was then water-jet cut into the desired geometry and notch length. Usable notch length and optimum loading rate was determined by testing a series of specimens. All testing was conducted at an OSU lab using a universal testing machine with Digital Image Correlation (DIC) data collected. Specimens were preloaded and matrix compression initiation and propagation data collected until tensile failure occurred on the back edge of the specimen. Testing showed that shorter notch lengths result in inconsistent data and longer in effective initiation but limited propagation due to reduced ligament length. Testing suggested that a speed less than 5 mm/min gave the best results as faster displacement rates caused less crack propagation to occur, while increasing the likelihood of the specimen to fail in tension along its back edge. Through the use of these guidelines, researchers are able to manufacture and use an effective test specimen for the investigation of matrix compression damage initiation and propagation.

Experimental Characterization of the Fiber Angles of Multiple Curved Laminate Segments Using Prepreg-Based Carbon Fiber Reinforced Polymers as a Structure for a Non-Engaging Bellows Coupling

2019 ◽  
Vol 809 ◽  
pp. 555-562
Author(s):  
Christian Oblinger ◽  
André Baeten ◽  
Klaus Drechsler
Keyword(s):  
Carbon Fiber ◽  
Rotation Axis ◽  
Fiber Reinforced Polymers ◽  
Main Task ◽  
Experimental Characterization ◽  
Fiber Reinforced ◽  
Carbon Fiber Reinforced Polymers ◽  
Reinforced Polymers ◽  
Carbon Fiber Reinforced

This paper deals with the experimental characterization of the fiber angles of multiple curved laminate segments using prepreg-based carbon fiber reinforced polymers as a structure for a non-engaging bellows coupling. The main task of this generic shaft coupling is the torsionally stiff torque transmission and the compensation of axial displacement as well as the angular misalignment of metallic shafts. The multiple curved structure can be manually draped by several cut segments using epoxy-based fabric prepreg. Moreover, the intended initial fiber orientation of the laminate is ±45° with respect to the rotation axis of the structure. For the experimental determination of the local fiber angles various CFRP cut segments were defined as CFRP specimens with varying number of layers and constant width. All investigations were based on cured CFRP specimens. The measurements were performed with a robot-assisted optical surface sensor and an optical digital microscope. The influence of the manual draping process according to the z-method could be quantitatively determined by the fiber angle measurements.

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