Generation and use of standardised load spectra and load–time histories

Two types of glass fiber reinforced plastic (GFRP) composites were fabricated viz., GFRP with neat epoxy matrix (GFRP-neat) and GFRP with hybrid modified epoxy matrix (GFRP-hybrid) containing 9 wt. % of rubber microparticles and 10 wt. % of silica nanoparticles. Fatigue tests were conducted on both the composites under the WISPERX load sequence. The fatigue life of the GFRP-hybrid composite was about 4-5 times higher than that of the GFRP-neat composite. The underlying mechanisms for improved fatigue performance are discussed. A reasonably good correlation was observed between the experimental fatigue life and the fatigue life predicted under the spectrum loads.Keywords: glass fiber composite, silica nanoparticle, rubber particle, spectrum fatigue. * Corresponding author: Tel. +91-80-2508 6310; Fax: +91-80-2508 6301 E-mail address: manjucm@nal.res.in (CM Manjunatha) 2 INTRODUCTIONDue mainly to their high specific strength and stiffness, continuous fiber reinforced plastic (FRP) composites are widely used in various structural applications such as airframes, wind turbines, ship hulls, etc. Such composite structural components experience variable amplitude or spectrum fatigue loads in service. Hence, the fatiguedurability of the composite materials under spectrum loads is an important requirement in these applications.Engineering polymer matrix composite materials generally consist of continuous glass or carbon fibers embedded in a thermosetting epoxy polymer. The epoxy polymer, being an amorphous and highly cross-linked material, is relatively brittle and exhibits a relatively poor resistance to crack initiation and growth, thus affecting the overall mechanical properties, including the fatigue and fracture behavior of FRP composites.One of the ways to improve the mechanical properties of FRPs is to add a second phase of fillers into the epoxy matrix.Incorporation of various types of micro-and nano-sized spherical, fibrous and layered fillers into the epoxy has been shown to improve the mechanical properties of composites [1][2][3]. Considerable improvements in the strength and stiffness [4], and dramatic improvements in the fracture toughness [3][4][5] EXPERIMENTAL Materials and ProcessingThe materials used and the processing employed to manufacture GFRP composites are briefly explained in this section. However, a detailed description of the materials and processing can be found in [24]. The epoxy resin used was LY556 from Huntsman, which is a diglycidyl ether of bisphenol A (DGEBA) resin. The silica (SiO 2 )nanoparticles were obtained as a colloidal silica sol with a concentration of 40 wt.% in LY556 from Nanoresins. The reactive liquid rubber was a carboxyl-terminated butadiene-acrylonitrile (CTBN) rubber, obtained from Nanoresins as a 40 wt.% CTBN-LY556 epoxy adduct. The curing agent was an accelerated methylhexahydrophthalic acid anhydride, HE600 from Nanoresins. The E-glass fiber cloth was a non-crimp-fabric (NCF) with an areal weight of 450 g/m 2 .The required quantity of the neat epoxy resin, th...

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“…The spectrum load sequence used was a wind turbine load sequence, WISPERX [29,30], as shown in Fig. 2.…”

Section: Spectrum Fatiguementioning

confidence: 99%

Enhanced fatigue behavior of a glass fiber reinforced hybrid particles modified epoxy nanocomposite under WISPERX spectrum load sequence

Manjunatha

Bojja

Jagannathan

et al. 2013

International Journal of Fatigue

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“…Heuler & al. [12,13,14,15] published a comprehensive review where each cited example is collected with its own purpose, the intended structural application, a brief qualification, and some more technical details like the block size.…”

Section: Standard Load Spectramentioning

confidence: 99%

“…According to [13,14], we make use of the following equation: (6) where the pattern of the spectrum is based on an exponential law and ν is the sole spectrum parameter, called the shape exponent. This equation may be plotted in a dimensionless field, see figure 4, considering the amplitude load ratio r i = S i / S max on the Y-axis and the occurrences ratio log H i / log H 0 on the X-axis.…”

Section: Standard Load Spectramentioning

confidence: 99%

Load spectra and fatigue damage: applications to the automotive industry

Facchinetti

2018

MATEC Web Conf.

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Abstract. High cycle fatigue behaviour of materials is historically assessed with constant amplitude and variable amplitude loads, respectively. Thus, a long-lasting debate is extremely active in the academic community, trying to link experimental results coming from these different approaches. Overcoming all this, since the 1970s several industrial fields have been choosing to consider representative customer load spectra (in terms of amplitude, not frequency) as the best way to test both materials and structures. In particular, the automotive industry makes use of specific car loading spectra, regularly fed by the customer knowledge and practised on proving grounds. This paper presents a highlight on such spectra, neglecting any sequence effect of the load time history, thus accepting the Palmgren-Miner's rule as an assumption. Whereas a recent communication on this very topic focused on the basic occurrence spectra, which is absolutely independent from the material properties of the car parts, here we deal with the final damage assessment. Obviously, it is worth knowing which part of the spectrum is mainly responsible for the most relevant fatigue damage.

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“…The main parameters of the machine are given in Table 1. The stator core of the IPMSM used in the in-wheel motor system may deform because of the impacting loads from the excitations of different road surfaces [23][24][25]. The relationship between the magnitude of the deformation and the impacting loads will be discussed in the further investigations.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Vibrations in Interior Permanent Magnet Synchronous Motors Considering Air-Gap Deformation

Chai

Song

et al. 2017

Energies

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This paper studies the non-uniform air-gap caused by stator and rotor deformations, together with its effects on the spatial and temporal spectrum of the radial magnetic force density in an interior permanent magnet synchronous motor (IPMSM). According to the mathematical model of the deformed air-gap length, the superposition method is adopted to derive the air-gap permeance. Then, the formulas of the magnetic flux field and radial force density of the IPMSM considering air-gap deformation are obtained. Considering the stator oval deformation and the rotor centrifugal distortion in the electromagnetic finite element models (FEMs), the finite element analysis (FEA) and experiments of the investigated IPMSM are carried out to verify the results obtained by the theoretical analysis at different operations. Finally, the mathematical correlation between air-gap deformation and electromagnetic vibration is obtained. The result is helpful in solving problems of mutual influence between electromagnetic and mechanical characteristics during the optimization design of IPMSM.

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Generation and use of standardised load spectra and load–time histories

Cited by 186 publications

References 16 publications

Enhanced fatigue behavior of a glass fiber reinforced hybrid particles modified epoxy nanocomposite under WISPERX spectrum load sequence

Enhanced fatigue behavior of a glass fiber reinforced hybrid particles modified epoxy nanocomposite under WISPERX spectrum load sequence

Load spectra and fatigue damage: applications to the automotive industry

Analysis of Vibrations in Interior Permanent Magnet Synchronous Motors Considering Air-Gap Deformation

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