Investigation of the fatigue behavior of thermoplastic composites by load increase tests

2020 ◽  
pp. 002199832095452
Author(s):  
Andreas Baumann ◽  
Sebastian Backe ◽  
Joachim Hausmann
Keyword(s):  
Fatigue Behavior ◽  
Numerical Data ◽  
Fatigue Loading ◽  
Polyamide 6 ◽  
Heat Emission ◽  
Thermoplastic Composites ◽  
Failure Behavior ◽  
Glass Fiber Reinforced ◽  
The Matrix ◽  
Load Increase

Fatigue is one major load case in many structures for transport applications. New materials often lack the necessary data base for a fast application in cyclic loaded components due to time consuming testing series. The aim of this study is the evaluation of the load increase test as method to determine a possible fatigue limit of glass fiber reinforced polyamide 6. Under the working hypothesis that cracks are the main contributors for heat emission, the results show that the investigated material exhibits a different behavior in comparison to thermosets. Instead of crack formation experimental and numerical data indicate that the matrix relaxes under fatigue loading. This relaxation could potentially lead to crack prevention but might also result in the observed sudden failure behavior of the material. These findings suggest a totally different behavior of thermoplastic composites under fatigue loading.

scholarly journals Thermoplastic Reaction Injection Pultrusion for Continuous Glass Fiber-Reinforced Polyamide-6 Composites

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 463 ◽  
Author(s):  
Ke Chen ◽  
Mingyin Jia ◽  
Hua Sun ◽  
Ping Xue
Keyword(s):  
Mechanical Properties ◽  
Glass Fiber ◽  
High Speed ◽  
Flexural Modulus ◽  
Polyamide 6 ◽  
Thermoplastic Composites ◽  
Fiber Reinforced ◽  
Pultrusion Process ◽  
Glass Fiber Reinforced ◽  
Pultruded Composites

In this paper, glass fiber-reinforced polyamide-6 (PA-6) composites with up to 70 wt% fiber contents were successfully manufactured using a pultrusion process, utilizing the anionic polymerization of caprolactam (a monomer of PA-6). A novel thermoplastic reaction injection pultrusion test line was developed with a specifically designed injection chamber to achieve complete impregnation of fiber bundles and high speed pultrusion. Process parameters like temperature of injection chamber, temperature of pultrusion die, and pultrusion speed were studied and optimized. The effects of die temperature on the crystallinity, melting point, and mechanical properties of the pultruded composites were also evaluated. The pultruded composites exhibited the highest flexural strength and flexural modulus, reaching 1061 MPa and 38,384 MPa, respectively. Then, effects of fiber contents on the density, heat distortion temperature, and mechanical properties of the composites were analyzed. The scanning electron microscope analysis showed the great interfacial adhesion between fibers and matrix at 180 °C, which greatly improved the mechanical properties of the composites. The thermoplastic reaction injection pultrusion in this paper provided an alternative for the preparation of thermoplastic composites with high fiber content.

Damage Assessment of Similar Martensitic Welds Under Creep, Fatigue and Creep-Fatigue Loading

2020 ◽  
Author(s):  
Thorben Bender ◽  
Andreas Klenk ◽  
Stefan Weihe
Keyword(s):  
Base Metal ◽  
Fatigue Behavior ◽  
Base Material ◽  
Fatigue Loading ◽  
Design Guidelines ◽  
Failure Behavior ◽  
Martensitic Steels ◽  
Viscoplastic Material ◽  
Local Strains ◽  
Creep Fatigue

Abstract For the assessment of welds under high-temperature conditions in the creep or creep-fatigue regimes, the knowledge on the damage location and its temporal evolution are of high importance. The failure behavior of similar welds of ferritic-martensitic steels in the creep regime is well known. For creep-fatigue loading, the behavior of welds is still subject to research but it seems that the heat affected zone (HAZ) limits the lifetime of welded components as well. This local failure behavior is not reflected in design guidelines using weld reduction factors or in typical assessment approaches. The evaluation of local strains and stresses in the HAZ is unavoidable. For the improvement of design and inspection guidelines, a more detailed consideration of weld behavior is of interest. In this paper, an overview of current developments in the assessment of welds under creep, fatigue, and creep-fatigue loading conditions is given. An assessment approach for creep damage and failure, including the prediction of rupture time and location, is presented. The assessment is based on numerical analyses considering the different behavior of base material and HAZ represented by three different subzones. The approach is validated with the simulation of a uniaxial cross weld, creep crack, and component tests. Whereas the creep behavior of the HAZ compared to base metal is quite well known, there is only little knowledge of their fatigue behavior. Using a set of fatigue tests on HAZ, base metal specimens and cross weld specimens, the influence of fatigue and creep-fatigue loading on the lifetime and failure location of a weld will be discussed. For the numerical simulations, a viscoplastic material law of Chaboche type is used and an evaluation of the local strains in the HAZ allows an attempt to explain the observed failure locations.

scholarly journals Fatigue Behavior of 3D Braided Composites Containing an Open-Hole

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2147
Author(s):  
Shuangqiang Liang ◽  
Qihong Zhou ◽  
Haiyang Mei ◽  
Ge Chen ◽  
Frank Ko
Keyword(s):  
Cross Section ◽  
Fatigue Behavior ◽  
Fatigue Loading ◽  
Fatigue Properties ◽  
Failure Behavior ◽  
Braided Composites ◽  
Damage Area ◽  
3D Braided Composites ◽  
Mechanical Performances ◽  
Braiding Angle

The static and dynamic mechanical performances of notched and un-notched 3D braided composites were studied. The effect of longitudinal laid-in yarn was investigated in comparison with low braiding angle composites. The specimens were fatigue tested for up to millions of cycles, and the residual strength of the samples that survived millions of cycles was tested. The cross-section of the 3D braided specimens was observed after fatigue loading. It was found that the static and fatigue properties of low angle 3D braided behaved better than longitudinally reinforced 3D braided composites. For failure behavior, pure braids contain damage better and show less damage area than the braids with longitudinal yarns under fatigue loading. More cracks occurred in the 3D braided specimen with axial yarn cross-section along the longitudinal and transverse direction.

scholarly journals Micromechanical Modeling Tensile and Fatigue Behavior of Fiber-Reinforced Ceramic-Matrix Composites Considering Matrix Fragmentation and Closure

2021 ◽  
Vol 5 (7) ◽  
pp. 187
Author(s):  
Longbiao Li
Keyword(s):  
Fatigue Behavior ◽  
Constitutive Models ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Fatigue Loading ◽  
Micromechanical Modeling ◽  
Interface Debonding ◽  
Matrix Composites ◽  
Fiber Reinforced ◽  
The Matrix

In this paper, micromechanical constitutive models are developed to predict the tensile and fatigue behavior of fiber-reinforced ceramic-matrix composites (CMCs) considering matrix fragmentation and closure. Damage models of matrix fragmentation, interface debonding, and fiber’s failure are considered in the micromechanical analysis of tensile response, and the matrix fragmentation closure, interface debonding and repeated sliding are considered in the hysteresis response. Relationships between the matrix fragmentation and closure, tensile and fatigue response, and interface debonding and fiber’s failure are established. Experimental matrix fragmentation density, tensile curves, and fatigue hysteresis loops of mini, unidirectional, cross-ply, and 2D plain-woven SiC/SiC composites are predicted using the developed constitutive models. Matrix fragmentation density changes with increasing or decreasing applied stress, which affects the nonlinear strain of SiC/SiC composite under tensile loading, and the interface debonding and sliding range of SiC/SiC composite under fatigue loading.

The Effect of Surface Treatment on the Mechanical Properties of Glass Fiber Reinforced Polyamide 6 Composite

2011 ◽  
Vol 66-68 ◽  
pp. 866-869
Author(s):  
Jun Bao ◽  
Jian Li
Keyword(s):  
Fatigue Strength ◽  
Glass Fiber ◽  
Fiber Surface ◽  
Tensile Tests ◽  
Polyamide 6 ◽  
Fatigue Tests ◽  
Fiber Reinforced ◽  
Fiber Concentration ◽  
Glass Fiber Reinforced ◽  
The Matrix

The effect of fiber surface modification on the fatigue strength of a glass fiber reinforced polyamide-6 has been investigated. Tension axial fatigue tests were conducted with specimens extracted from injection moulded plates. Results show the variation of the fatigue strength as a function of the fiber concentration. The experimental data, the tensile tests have shown the effective improvement of interfacial adhesion between the fiber surface and the matrix.

scholarly journals Investigation of Fatigue Behavior of Three Dimensional Interlock Composites by Time-Lapse Micro-Computed Tomography

2021 ◽  
Vol 6 (1) ◽  
pp. 14
Author(s):  
Christophe Cruanes ◽  
Keerthi Krishna Parvathaneni ◽  
Dmytro Vasiukov ◽  
Chung Hae Park
Keyword(s):  
Computed Tomography ◽  
Fatigue Behavior ◽  
Three Dimensional ◽  
Injection Pressure ◽  
Fatigue Loading ◽  
Time Lapse ◽  
Fatigue Performance ◽  
Micro Computed Tomography ◽  
The Matrix ◽  
Micro Tomography

The mechanism of the crack propagation in three dimensional (3D) glass-fiber warp interlock epoxy composites under fatigue loading was investigated via time-lapse micro-computed tomography (µCT) observations. Two different composite samples were manufactured by means of a resin transfer molding (RTM) process under two different constant injection pressure conditions to generate intrayarn and interyarn voids separately. Fatigue loads were applied by blocks of 105 cycles and followed by µCT measurements. Regions of interest for micro tomography scans were selected based on hot spots detected by infrared thermography. After the analysis of the obtained data, it was observed that detectable cracks were generally initiated by debonding in the zone between two adjacent warp yarns and grew along their interface. Then, these cracks propagated along one of the warp yarns aligned in the loading direction while remaining in the middle of the specimen cross-section. The coalescence of the cracks and further propagation to the weakest zones were observed around and after the middle lifetime. Finally, we demonstrated the influence of the void defects at different material scales. I was found that interyarn voids have relatively little influence on the fatigue performance whereas they can, sometimes, attract and deviate cracks in the matrix zone between adjacent yarns. It was also shown that the intrayarn voids are crucial to degenerate the fatigue performance of the yarns at the micro-scale.

scholarly journals Fatigue Behavior of PBO FRCM Composite Applied to Concrete Substrate

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2368
Author(s):  
Angelo Savio Calabrese ◽  
Tommaso D’Antino ◽  
Pierluigi Colombi ◽  
Christian Carloni ◽  
Carlo Poggi
Keyword(s):  
Fatigue Life ◽  
Fatigue Behavior ◽  
Fatigue Loading ◽  
Interface Shear ◽  
Moment Capacity ◽  
Bond Behavior ◽  
The Matrix ◽  
Externally Bonded ◽  
Set Up ◽  
The Moment

Several reinforced-concrete (RC) structural elements are subjected to cyclic load, such those employed in highway and railroad bridges and viaducts. The durability of these elements may be reduced as a consequence of fatigue, which mainly affects the steel reinforcement. The use of externally bonded (EB) fiber-reinforced cementitious matrix (FRCM) composites allows the moment capacity to be shared by the internal reinforcement and the EB composite, thus increasing the fatigue life of the strengthened RC member. The effectiveness of EB FRCM composites is related to the composite bond properties. However, limited research is currently available on the effect of fatigue on the bond behavior of FRCM-substrate joints. This study provides first the state of the art on the fatigue behavior of different FRCM composites bonded to a concrete substrate. Then, the fatigue bond behavior of a polyparaphenylene benzo-bisoxazole (PBO) FRCM is experimentally investigated using a modified beam test set-up. The use of this set-up provided information on the effect of fiber-matrix interface shear and normal stresses on the specimen fatigue bond behavior. The results showed that fatigue loading may induce premature debonding at the matrix-fiber interface and that stresses normal to the interface reduce the specimen fatigue life.

scholarly journals A Finite Element based Micromechanical Model to Simulate Fatigue Damage Development in Open-Hole Laminated Composites

2020 ◽  
Author(s):  
mohammad ghalandari ◽  
Hossein Toozandehjani ◽  
Ibrahim Mahariq
Keyword(s):  
Finite Element ◽  
Fatigue Damage ◽  
Fatigue Behavior ◽  
Micromechanical Model ◽  
Laminated Composite ◽  
Fatigue Loading ◽  
Element Model ◽  
Damage Development ◽  
Damage Degree ◽  
The Matrix

A micromechanical model is implemented to indicate the progressive fatigue problem of a laminated composite with a central circular hole under fatigue loading based on a finite element model. The mechanical properties of the composite lamina are represented based on the characteristics of the fiber and the matrix through a micromechanics model. An appropriate algorithm is then adopted to simulate fatigue damage development in the composite lamina. According to this algorithm, the stress field of the composite subjected to fatigue load is initially obtained using the finite element method. Finally, the predicted results of the stresses in the constituents i.e. fiber and matrix are determined according to the micromechanical bridging model. Finally applying proper damage driving relations leads to damage degree in each element. The proposed model is proven to be successful in the observation of the fatigue behavior with stiffness degradation in each element of the composite in each cycle. Results are reported and validated using those micromechanical models and experimental data available in the literature.

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