Experimental Characterization of Matrix Cracking Behavior in Thermally Cycled CFRP Laminates

2002 ◽  
Vol 11 (3) ◽  
pp. 287-305 ◽  
Author(s):  
Shinji Ogihara ◽  
Akira Kobayashi ◽  
Takamoto Ishiguro ◽  
Nobuo Otani
Keyword(s):  
Thermal Cycling ◽  
Crack Density ◽  
Tensile Loading ◽  
Matrix Crack ◽  
Matrix Cracking ◽  
Thermal Cycles ◽  
Critical Energy Release Rate ◽  
Cracking Behavior ◽  
Cfrp Laminates ◽  
The Matrix

The effect of thermal cycling on the mechanical properties of composite materials is an important issue in engineering, especially in their applications to the space environment. The present study concerned with the experimental study of both the thermal cycling induced matrix cracking and the effect of thermal cycling on the matrix cracking behavior under tensile loading in CFRP laminates. Two kinds of carbon/epoxy systems, T800H/3631 and T300/2500, are used for the laminate configurations of (0/90)s and (90/0)s. The specimens are thermally cycled between −196 and 100°C. Thermal cycling tests are performed up to 1000 cycles. The polished edge surfaces of specimens are examined by the replica technique, and then the matrix crack density is measured as a function of the number of thermal cycles. It is found that the first matrix cracking in (0/90)s and (90/0)s laminates occurs at almost the same numbers of thermal cycles. It is also found that the matrix crack density increases more rapidly in (0/90)s laminates than in (90/0)s laminates in both material systems. To investigate the effect of thermal cycling on matrix cracking behavior under tensile loading, a series of tensile tests on thermally cycled specimens are performed. The effect of thermal cycling on matrix cracking under tension is evaluated in terms of the change in the critical energy release rate and the critical stress for matrix cracking.

Effects of thermal cycling on phenylethynyl-terminated PMDA-type asymmetric polyimide composites

2018 ◽  
Vol 31 (7) ◽  
pp. 861-871
Author(s):  
Yixiang Zhang ◽  
Masahiko Miyauchi ◽  
Steven Nutt
Keyword(s):  
Thermal Cycling ◽  
Mechanical Degradation ◽  
Thermal Cycles ◽  
Oxidative Aging ◽  
Short Beam ◽  
Beam Shear ◽  
Thermally Driven ◽  
The Matrix ◽  
Service Environments ◽  
Thermal Oxidative Aging

The effects of thermal cycling on a polymerized monomeric reactant (PMR) type polyimide (TriA X) reinforced with carbon fibers were investigated. Composite specimens were subjected to 2000 thermal cycles between −54°C and 232°C. At 400-cycle intervals, laminates were inspected for microcracks, and glass transition temperature ( T g) and short-beam shear (SBS) strength were measured. The composites did not exhibit microcracks after thermal cycling, although after 2000 thermal cycles, mechanical properties of the matrix declined slightly. The matrix degradation decreased the resistance to microcracking upon further loading. No effects of thermal oxidative aging were observed from thermal cycling, and thermally driven fatigue and creep were identified as the primary and secondary factors inducing mechanical degradation of the matrix. T g of the composites exhibited no change after 2000 cycles, while the SBS strength decreased slightly (3–9%). The results highlight the potential for use of TriA X composites as long-term structural components in high-temperature service environments.

In situ x-ray CT under tensile loading using synchrotron radiation

1995 ◽  
Vol 10 (2) ◽  
pp. 381-386 ◽  
Author(s):  
T. Hirano ◽  
K. Usami ◽  
Y. Tanaka ◽  
C. Masuda
Keyword(s):  
Synchrotron Radiation ◽  
Tensile Loading ◽  
Ct Images ◽  
Matrix Cracking ◽  
Alloy Matrix ◽  
X Ray ◽  
Sic Fibers ◽  
Matrix Cracks ◽  
The Matrix

Internal damage in metal matrix composite (MMC) under static tensile loading was observed by in situ x-ray computed tomography based on synchrotron radiation (SR-CT). A tensile testing sample stage was developed to investigate the fracture process during the tensile test. Aluminum alloy matrix composites reinforced by long or short SiC fibers were used. The projection images obtained under tensile loading showed good performance of the sample stage, and matrix deformation and breaks of the long SiC fibers could be observed. In the CT images taken at the maximum stress just before failure, debondings of the short SiC fibers to the matrix, many pullouts of the fibers, and matrix cracking could be clearly observed. The in situ SR-CT allowed the observation of generation and growth of such defects under different tensile stress levels. The results from the nondestructive observation revealed that the MMC was broken by propagation of the matrix cracks which might be caused by stress concentration at the ends of the short fibers. A three-dimensional CT image reconstructed from many CT images provided easy understanding of the fiber arrangement, crack shape, and form of the void caused by fiber pullout. In situ SR-CT is a useful method for understanding failure mechanisms in advanced materials.

Analysis of Formation of the Critical State in Tensile Failure of Unidirectional Composites

2015 ◽  
Author(s):  
Linqi Zhuang ◽  
Ramesh Talreja
Keyword(s):  
Tensile Loading ◽  
Matrix Cracking ◽  
Fracture Plane ◽  
Fe Model ◽  
Load Bearing Capacity ◽  
Fiber Failure ◽  
Load Bearing ◽  
Critical Fracture ◽  
The Matrix ◽  
Fiber Breaks

Unidirectional (UD) composites are building blocks in most load bearing structural components for lightweight applications in aerospace, automotive and wind energy industries. The loss of the structural load bearing capacity is governed by the instability of the fiber breakage process in the UD composites. When subjected to increasing or repeated tensile loading along fiber direction, the first failure event within these composites occurs as discrete fibers break at weak points followed by fiber/matrix debonding due to high stress concentration caused by fiber breaks. Upon further loading, or on repeated loading, more fiber breaks occur along with other accumulated damage events such as debond growth and matrix cracking. Final failure of a UD composite occurs when a critical fracture plane is formed by interconnecting individual broken fibers and associated debonding through matrix cracking. This failure process has emerged from numerous experimental studies, which also suggest that the critical fracture plane contains only a small number of broken fibers for commonly used composites such as glass/epoxy and carbon/epoxy. However, the mechanisms underlying the critical fracture plane formation are not clear. As the first step to clarify the creation of a critical fracture plane, the conditions for connectivity of a broken fiber end with neighboring broken fibers is studied in this work. In order to investigate the local stress field surrounding the broken fiber, a finite element (FE) model is constructed in which six neighboring fibers are placed as a ring of concentric axisymmetric cylinder embedded in the matrix. The discrete fiber region is surrounded by a concentric outer cylinder ring of homogenized composite. The entire FE model is subjected to axial tensile loading. To account for the consequence of the stress enhancement at the broken fiber end, a debond crack at the fiber/matrix interface extending a short distance from the fiber end is included in the analysis. Realizing that the debond crack by itself would not connect with other fiber failures, focus of the stress and failure analysis is placed on deviation of the debond crack laterally into the matrix. For this purpose, matrix cracking in two possible modes — ductile and brittle — is considered, Energy based criteria are used to study the competition between the cracking modes and the crack path into the matrix from the end of debond to the neighboring fibers is determined. Next the failure of the neighboring fibers caused by the intense stress field accompanying the matrix cracks is studied. The conditions for generating a plane connecting the initially broken fiber end to subsequent fiber failures are finally determined. Further ongoing studies are aimed at clarifying the limiting conditions for avoiding the fiber failure criticality, and thereby improving the load bearing capacity of UD composites. The statistical considerations regarding fiber failure will also be incorporated in these studies.

Influence of Interfacial Characteristics on the Mechanical Properties of Continuous Fiber Reinforced Nial Composites

1992 ◽  
Vol 273 ◽  
Author(s):  
Randy R. Bowman
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Thermal Cycling ◽  
Oxidation Resistance ◽  
Cyclic Oxidation ◽  
Room Temperature ◽  
Matrix Cracking ◽  
High Temperature Strength ◽  
Interfacial Bond ◽  
The Matrix

ABSTRACTAs part of a study to assess NiAl-based composites as potential high-temperature structural materials, the mechanical properties of polycrystalline NiAl reinforced with 30 vol.% continuous single crystal Al2O3 fibers were investigated. Composites were fabricated with either a strong or weak bond between the NiAl matrix and Al2O3 fibers. The effect of interfacial bond strength on bending and tensile properties, thermal cycling response, and cyclic oxidation resistance was examined. Weakly-bonded fibers increased room-temperature toughness of the composite over that of the matrix material but provided no strengthening at high temperatures. With effective load transfer, either by the presence of a strong interfacial bond or by remotely applied clamping loads, Al2O3 fibers increased the high-temperature strength of NiAl but reduced the strain to failure of the composite compared to the monolithic material. Thermal cycling of the weakly-bonded material had no adverse effect on the mechanical properties of the composite. Conversely, because of the thermal expansion mismatch between the matrix and fibers, the presence of a strong interfacial bond generated residual stresses in the composite that lead to matrix cracking. Although undesirable under thermal cycling conditions, a strong interfacial bond was a requirement for achieving good cyclic oxidation resistance in the composite. In addition to the interfacial characterization, compression creep and room temperature fatigue tests were conducted on weakly-bonded NiAl/Al2O3 composites to further evaluate the potential of this system. These results demonstrated that the use of A12O3 fibers was successful in improving both creep and fatigue resistance.

scholarly journals Simulation Study of the Damage Mechanisms Appearing in a Cross Ply Composite Material Loaded in Uniaxial Tension

2021 ◽  
Vol 349 ◽  
pp. 01001
Author(s):  
Eleftherios Tsivolas ◽  
Leonidas N. Gergidis ◽  
Alkiviadis S. Paipetis
Keyword(s):  
Composite Material ◽  
Uniaxial Tension ◽  
Multiple Scales ◽  
Crack Density ◽  
Transversely Isotropic ◽  
Matrix Cracking ◽  
Viscous Effects ◽  
Damage Mechanisms ◽  
The Matrix ◽  
Final Crack

The objective of this paper is to predict the different damage mechanisms in multiple scales that can occur in a cross ply composite material loaded in uniaxial tension. The simulated composite material consists of four epoxy-glass fibre layers [0/90]s and the material of each layer is transversely isotropic with viscous effects that occurred from micromechanical homogenization using Mori-Tanaka formulation, extended for visco-elastic materials. For the prediction of the cracking and interlaminar delamination, cohesive contacts were used and the final crack density results were compared with the corresponding experimental ones. Finally a microscale analysis was performed in a Representative Volume Element (RVE) to observe the matrix cracking behaviour in smaller scale.

Matrix Crack Detection of CFRP Laminates in Cryogenic Temperature Using Electrical Resistance Change Method

2006 ◽  
Vol 321-323 ◽  
pp. 873-876 ◽  
Author(s):  
Akira Todoroki ◽  
Kazuomi Omagari ◽  
Masahito Ueda
Keyword(s):  
Electrical Resistance ◽  
Cryogenic Temperature ◽  
Matrix Crack ◽  
Fuel Tank ◽  
Matrix Cracking ◽  
Resistance Change ◽  
Cfrp Laminates ◽  
Resistance Increase ◽  
Matrix Cracks ◽  
Electrical Resistance Change

For a cryogenic fuel tank of a next generation rocket, a Carbon Fiber Reinforced Plastic (CFRP) laminated composite tank is one of the key technologies. For the fuel tank made from the laminated composites, matrix cracks are significant problems that cause leak of the fuel. In the present paper, electrical resistance change method is adopted to monitor the matrix cracking of the CFRP laminate. Previous studies show that tension load in fiber direction causes electrical resistance increase due to the piezoresistivity of the carbon fibers, and fiber breakages also cause the electrical resistance increase of the CFRP laminates. In order to distinguish the electrical resistance changes due to matrix cracking from those due to the piezoresistivity and the fiber breakages, residual electrical resistance change under the complete unloading condition is employed in the present study. Experimental investigations were performed using cross-ply laminates in cryogenic temperature. As a result, it can be revealed that the residual electrical resistance change is a useful indicator for matrix crack monitoring of the cross-ply CFRP laminates.

scholarly journals Investigation on the Behavior of Tensile Damage Evolution in T700/6808 Composite Based on Acoustic Emission Technology

2016 ◽  
Vol 2016 ◽  
pp. 1-9
Author(s):  
Weihan Wang ◽  
Weifang Zhang ◽  
Shengwang Liu ◽  
Xiaoshuai Jin
Keyword(s):  
Acoustic Emission ◽  
Damage Evolution ◽  
Tensile Loading ◽  
Matrix Cracking ◽  
Composite Analysis ◽  
Fiber Breakage ◽  
Interface Damage ◽  
Initial Stage ◽  
The Matrix ◽  
Acoustic Emission Technology

T700/6808 composite has been widely used in aerospace field and the damage in composite will seriously influence the safety of aircraft. However, the behavior of damage evolution in T700/6808 composite when it suffered from tensile loading is seldom researched. In this paper, the acoustic emission (AE) technology is employed to research the process of damage evolution in T700/6808 composite under tensile loading. Results show that the damage in T700/6808 composite is small in the initial stage of tensile loading, and main damage is the matrix cracking. The composite has serious damage in the middle stage of tensile loading, which mainly includes the matrix cracking and the interface damage as well as the fiber breakage. The number of fiber breakages decreases rapidly in the later stage of tensile loading. When it comes into the stage of load holding, the composite has relatively smaller damage than that in the stage of tensile loading, and the fiber breakage rarely occurs in the composite. Analysis of damage modes shows that the criticality of the matrix cracking and the interface damage is higher than the fiber breakage, which illustrates that the reliability of T700/6808 composite could be improved by the optimization of matrix and interface.

Initiation and Propagation of Impact-Induced Damage in CFRP Laminates

2007 ◽  
Vol 345-346 ◽  
pp. 437-440
Author(s):  
Seung Min Jang ◽  
Tadaharu Adachi ◽  
Akihiko Yamaji
Keyword(s):  
Impact Damage ◽  
Matrix Crack ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Element Analysis ◽  
Cfrp Laminates ◽  
Initiation And Propagation ◽  
Back Face ◽  
The Matrix ◽  
The Impact

This paper investigated the initiation and propagation characteristics of impact-induced damage in carbon-fiber-reinforced-plastic (CFRP) laminates with different stacking sequences and thicknesses under low-velocity impact. Impact force histories were measured with a drop-weight impact tester. A strain gauge was attached on the back face of CFRP laminates to measure exactly when a matrix crack on its back face was initiated. It was found from fractographic observation that impact-induced damage in CFRP laminates was initiated at the matrix crack on the back face of CFRP laminates due to bending deformation during impact. Finite element analysis was conducted using the impact forces derived from the experimental results of the impact test. Its results clarified that the tensile stress normal to the fiber on the back face of the specimen was the criterion to initiate impact damage in CFRP laminates.

scholarly journals Analysis of Local Delamination in A Cracked Composite Laminate Loaded in Tension

1993 ◽  
Vol 2 (6) ◽  
pp. 096369359300200
Author(s):  
J. Zhang ◽  
C. Soutis
Keyword(s):  
Composite Laminate ◽  
Crack Density ◽  
Strain Energy Release ◽  
Matrix Crack ◽  
Total Strain Energy ◽  
Element Analysis ◽  
The Matrix ◽  
Dimensional Finite Element ◽  
Elastic Fracture ◽  
Good Agreement

In the present paper the total strain energy release rate G associated with delaminations that initiate from a matrix crack in a [±θm/90n]s composite laminate is calculated using the potential energy approach in elastic fracture mechanics. The predictions are compared with a two-dimensional finite element analysis. It is found that for delamination lengths greater than two-ply thicknesses the theoretical and numerical results are in good agreement. The new model shows that G is affected by the matrix crack density and residual hygrothermal stresses.

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