Dynamic properties of hybrid composite structures based multiwalled carbon nanotubes
Introduction
Carbon nanotubes (CNT) reinforced laminate composites are being increasingly used in automotive, marine and aerospace applications due to their exceptional mechanical properties. Impact on composite structures has been an active research topic, with more than 400 papers using Taylor gun tests over the past 50 years [1]. Most investigations concentrated on determining the scenarios of damage and the dynamic yield stress [2], [3], [4]. Vieille et al. [5] present a comparative study on the impact behavior of woven-ply carbon fiber-reinforced thermoplastic and thermosetting composites. An inspection using microscope observation showed that the impact generates different form of damage: fiber breakage, inter-laminar and intra-ply damage. Mechanical properties and damage kinetics of laminate composites under higher-strain rate impact were presented in Refs. [6], [7]. Experimental results show that the strain rate has an important effect on the dynamic response of laminated panels. Griffiths and Martin [8] were interested in the dynamic behavior of a polymer matrix reinforced with unidirectional carbon fibers at high strain rates, in order to determine how the material properties depend on the volume fraction and orientation of the fibers. Fibers volume fractions ranging from 30 to 60% and various fibers orientation has been investigated experimentally for compression loading up to 200 MN m-3.
Anderson et al. [9] conducted Taylor impact tests to control the evolution of damage in specimens. Using Hopkinson bars, Bie et al. [10] studied the dynamic properties and fracture of carbon nanotubes/epoxy composites demonstrating a significant effect of CNTs on the composite properties. The composite specimens include randomly dispersed, 1 wt%, of functionalized and pristine CNT/epoxy composites. Experimental results show that the fracture modes depend on the CNT/epoxy interface and the CNTs reduce the extent of damage of epoxy. Previous studies investigated dynamic response of glass fiber reinforced polymer composites [11], dynamic tensile strengths of glass fibers reinforced epoxy polymers [12], and damage of a woven carbon fibers reinforced epoxy polymer composites with CNTs [13]. The CNTs were randomly dispersed in an epoxy resin. The samples were subjected to out-of-plane impact from which the energy dissipation capacity of the composites was evaluated. Incorporating CNTs into the textile increased the absorbed impact energy by 21%. The damage evolution differs for the laminates based on neat and CNTs enriched epoxy matrices. While the CNTs composites exhibited a multiple stage delamination and lesser amount of tow failure, the specimens with neat matrix delaminated abruptly. Authors show that these enhancements are owed to the improved fiber–matrix adhesion by implantation of CNTs. Recently, a novel systematic procedure to obtain the dynamic flow stress of a material at high strain rates using Taylor impact tests was proposed [14]. Taylor impact tests were conducted with 200 m/s, 253 m/s, and 305 m/s of speed projectile, and full-field ultra-high strain rates, high temperature, and large plastic deformation were determined. However, no or only very few references reported the impact behavior of hybrid laminated composites based CNTs using a Taylor gun.
This study presents an investigation on the dynamic behaviour of carbon fiber/epoxy polymers in order to understand the effect of CNTs on laminated composites. The aim is to engineer novel hybrid nanocomposites based on electrospun polybenzimidazole nanofibers (pNF) filled with MWCNTs which are applied as interlayer between composite plies. In addition, bismaleimide (BMI) resin system is added. It works as 3-dimensional bridges creating interconnect between nanotubes, fibers, and matrix polymer. We conducted an experimental study on the Taylor impact tests, where steel projectiles were fired with low velocity impacts; 5 and 7 m/s. Composite reinforced by reactive electrospun pNF filled with MWCNTs were considered and compared to pure pNF and neat carbon epoxy composite.
Section snippets
Materials
Polybenzimidazole (Mw. 29,000), 26% solution in dimethyl acetamide (DMAc) was obtained from PBI Performance Products Inc. (USA). PBI is a heterocyclic thermoplastic with excellent mechanical properties. Homide 250, a pre-polymer bismaleimide (BMI) resin system, 45% solution in n-methyl pirrolidone (NMP) was kindly supplied by HOS-Technik GmbH (Austria). BMI is a fusible duraplastic resin with a molecular weight of max. 30 000 g/mol. The product contains also oligomer and low molecular weight
Experimental testing and results
Carbon Fiber Reinforced Composites (CFRC) were prepared by sandwiching layer-by-layer carbon fabric and reactive electrospun nanofiber mats. Three different types of composites were compared. Control CFRC (MAT 1), and two other with PBI-BMI nanofiber mats with (MAT 3) and without MWCNTs (MAT 2). Composites reinforced with nanofiber mats were produced in concentration content of 35.7 wt%. For unfilled nanofibers and 37.5 wt% for MWCNT-containing nanofibers. Such different can be described by
Conclusion
Experimental studies of dynamic tests (low impact) were conducted on specimens of carbon/epoxy with and without of electrospun PBI-BMI nanofibermats and MWCNTs. This study was carried out to investigate the effect of CNTs addition on the mechanical properties of composites and the absorbed energy impact. Furthermore, the detection of the maximum force and the damaged size of the specimens after the impact tests were done. The following conclusions are drawn from this study:
- •
Inclusion of reactive
References (19)
- et al.
Mechanical behavior and damage kinetics of woven E-glass/vinylester laminate composites under high strain rate dynamic compressive loading: experimental and numerical investigation
Int. J. Impact Eng.
(2016) - et al.
Experimental and numerical investigation on the deformation and failure behavior in the Taylor test
Mater. Des.
(2011) - et al.
About the impact behavior of woven-ply carbon fiber-reinforced thermoplastic and thermosetting-composites: a comparative study
Compos. Struct.
(2013) - et al.
Progressive failure analysis and energy-absorbing experiment of composite tubes under axial dynamic impact
Compos. Part B Eng.
(2016) - et al.
Dynamic fracture of carbon nanotube/epoxy composites under high strain-rate loading
Compos. Part A
(2015) - et al.
Shock response of a glass-fiber reinforced polymer composite
Compos. Struct.
(2003) - et al.
The response of a glass fibers reinforced epoxy composite to an impact loading
Int. J. Solids Struct.
(2004) - et al.
Mechanical characterization and impact damage assessment of a woven carbon fiber reinforced carbon nanotube-epoxy composite
Compos. Sci. Technol.
(2013) - et al.
Characterization of flow stress at ultra-high strain rates by proper extrapolation with Taylor impact tests
Int. J. Impact Eng.
(2016)