scholarly journals Effects of moisture absorption on damage progression and strength of unidirectional and cross-ply fiberglass–epoxy composites

2018 ◽  
Vol 3 (1) ◽  
pp. 427-438
Author(s):  
Jake D. Nunemaker ◽  
Michael M. Voth ◽  
David A. Miller ◽  
Daniel D. Samborsky ◽  
Paul Murdy ◽  
...  

Abstract. Fiber-reinforced-polymer composites (FRPs) possess superior mechanical properties and formability, making them a desirable material for construction of large optimized mechanical structures, such as aircraft, wind turbines, and marine hydrokinetic (MHK) devices. However, exposure to harsh marine environments can result in moisture absorption into the microstructure of the FRPs comprising these structures and often degrading mechanical properties. Specifically, laminate static and fatigue strengths are often significantly reduced, which must be considered in design of FRP structures in marine environments. A study of fiberglass epoxy unidirectional and cross-ply laminates was conducted to investigate hygrothermal effects on the mechanical behavior of a common material system used in wind applications. Several laminates were aged in 50 ∘C distilled water until maximum saturation was reached. Unconditioned control and the saturated samples were tested in quasi-static tension with the accompaniment of acoustic emission (AE) monitoring. Cross-ply laminates experienced a 54 % reduction in strength due to moisture absorption, while unidirectional laminate strengths were reduced by 40 %. Stress–strain curves and AE activity of the samples were analyzed to identify changes in damage progression due to aging.

2018 ◽  
Author(s):  
Jake D. Nunemaker ◽  
Michael M. Voth ◽  
David A. Miller ◽  
Daniel D. Samborsky ◽  
Paul Murdy ◽  
...  

Abstract. Fiber-Reinforced-Polymer composites (FRP's) possess superior mechanical properties and formability, making them a desirable material for construction of large optimized mechanical structures, such as aircraft, wind turbines, and marine hydro kinetic (MHK) devices. However, exposure to harsh marine environments can result in moisture absorption into the microstructure of the FRP's comprising these structures and often degrading mechanical properties. Specifically, laminate static and fatigue strengths are often significantly reduced, which must be considered in design of FRP structures in marine environments. A study of fiber-glass epoxy unidirectional and cross-ply laminates was conducted to investigate hygrothermal effects on the mechanical behavior of a common material system used in wind applications. Several laminates were aged in 50 °C distilled water until maximum saturation was reached. Unconditioned control and the saturated samples were tested in quasi-static tension with the accompaniment of Acoustic Emission (AE) monitoring. Cross-ply laminates experienced 54 % reduction in strengths from due to moisture absorption, while unidirectional laminates strengths were reduced by 40 %. Stress-strain curves and AE activity of the samples were analyzed to identify changes in damage progression due to aging.


2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Kawaljit Singh Randhawa ◽  
Ashwin Patel

Purpose The mechanical and tribological properties of polymers and polymer composites vary with different environmental conditions. This paper aims to review the influence of humidity/water conditions on various polymers and polymer composites' mechanical properties and tribological behaviors. Design/methodology/approach The influence of humidity and water absorption on mechanical and tribological properties of various polymers, fillers and composites has been discussed in this paper. Tensile strength, modulus, yield strength, impact strength, COF and wear rates of polymer composites are compared for different environmental conditions. The interaction between the water molecules and hydrophobic polymers is also represented. Findings Pure polymer matrices show somewhat mixed behavior in humid environments. Absorbed moisture generally plasticizes the epoxies and polyamides and lowers the tensile strength, yield strength and modulus. Wear rates of PVC generally decrease in humid environments, while for polyamides, it increases. Fillers like graphite and boron-based compounds exhibit low COF, while MoS2 particulate fillers exhibit higher COF at high humidity and water conditions. The mechanical properties of fiber-reinforced polymer composites tend to decrease as the rate of humidity increases while the wear rates of fiber-reinforced polymer composites show somewhat mixed behavior. Particulate fillers like metals and advanced ceramics reinforced polymer composites exhibit low COF and wear rates as the rate of humidity increases. Originality/value The mechanical and tribological properties of polymers and polymer composites vary with the humidity value present in the environment. In dry conditions, wear loss is determined by the hardness of the contacting surfaces, which may not effectively work for high humid environments. The tribological performance of composite constituents, i.e. matrix and fillers in humid environments, defines the overall performance of polymer composite in said environments.


2018 ◽  
Vol 32 (11) ◽  
pp. 1525-1546 ◽  
Author(s):  
Yue Mu ◽  
Anbiao Chen ◽  
Guoqun Zhao ◽  
Yujia Cui ◽  
Jiejie Feng ◽  
...  

The fiber-reinforced polymer composites are important alternative for conventional structural materials because of their excellent comprehensive performance and weight reduction. The mechanical properties of such composite materials are mainly determined by the fiber orientation induced through practical manufacturing process. In the study, a through process modeling (TPM) method coupling the microstructure evolution and the mechanical properties of fiber-reinforced composites in practical processing is presented. The numerical methodology based on the finite volume method is performed to investigate three-dimensional forming process in the injection molding of fiber-reinforced composites. The evolution of fiber orientation distribution is successfully predicted by using a reduced strain closure model. The corresponding finite volume model for TPM is detailedly derived and the pressure implicit with splitting of operators (PISO) algorithm is employed to improve computational stability. The flow-induced multilayer structure is successfully predicted according to essential flow characteristics and the fiber orientation distribution. The mechanical properties of such anisotropy composites is further calculated based on the stiffness analysis and the Tandon–Weng model. The improvement of mechanical properties in each direction of the injection molded product are evaluated by using the established mathematical model and numerical algorithm. The influences of the geometric structure of injection mold cavity, the fiber volume fractions, and the fiber aspect ratios on the mechanical properties of composite products are further discussed. The mathematical model and numerical method proposed in the study can be successfully adopted to investigate the structural response of composites in practical manufacturing process that will be helpful for optimum processing design.


2018 ◽  
Vol 52 (23) ◽  
pp. 3173-3181 ◽  
Author(s):  
Kuldeep Agarwal ◽  
Suresh K Kuchipudi ◽  
Benoit Girard ◽  
Matthew Houser

Fiber reinforced polymer composites have been around for many decades but recently their use has started to increase in multiple industries such as automotive, aerospace, and construction. The conventional composite manufacturing processes such as wet lay-up, resin transfer molding, automatic lay ups etc. suffer from a lot of practical and material issues which have limited their use. The mechanical properties of the parts produced by such processes also suffer from variation that causes problems downstream. Composites based additive manufacturing processes such as Fused Deposition Modeling and Composite Filament Fabrication are trying to remove some of the barriers to the use of composites. Additive manufacturing processes offer more design and material freedom than conventional composite manufacturing processes. This paper compares conventional composite processes for the manufacturing of Epoxy-Fiberglass fiber reinforced polymers with composite filament fabrication based Nylon-Fiberglass fiber reinforced polymers. Mechanical properties such as tensile strength, elastic modulus, and fatigue life are compared for the different processes. The effect of process parameters on these mechanical properties for the composite filament fabrication based process is also examined in this work. It is found that the composite filament fabrication based process is very versatile and the parts manufactured by this process can be used in various applications.


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