Bilinear approach to tensile properties of flax composites in finite element analyses

Strohrmann, Katharina; Hajek, Manfred

doi:10.1007/s10853-018-2912-1

Cited by 15 publications

(15 citation statements)

References 30 publications

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“…At a standard head displacement rate of 2 mm.min -1 , the mean values of longitudinal apparent modulus (EL m1 ), strength ( ) and strain at failure ( ) are approximately 35 GPa, 387 MPa, and 1.52%. These values are in good agreement with the datasheet of the material provider and with data of literature collected on the same type of UD flax-epoxy composites [42,43]. Fig.…”

Section: Monotonic Tensile Behavioursupporting

confidence: 90%

About the fatigue endurance of unidirectional flax-epoxy composite laminates

Jeannin

Gabrion

Ramasso

et al. 2019

Composites Part B: Engineering

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Even if the knowledge on the fatigue behaviour of plant fibre composites has increased steadily in the last few years, some issues still remain open at the present time. Such is the case, for instance, of the high-cycle fatigue strength. Actually, most of the fatigue studies available in the open literature to date are limited to a maximum of 1-2 million cycles. All available stress-life plots exhibit linear trends with constant slope and does not reveal any fatigue limit for these given cycle numbers. So, this paper proposes to investigate the High-Cycle Fatigue behaviour of a flax-epoxy laminated composite. The effect of loading frequency is firstly evaluated on the Low-Cycle Fatigue behaviour using a multi-instrumented analysis including infrared thermography and acoustic emission. Results show that high frequency could be a suitable method to shorten the fatigue tests and study the High Cycle Fatigue behaviour of this type of composite material. Based on this result, high-frequency (30 Hz) is used to investigate the behaviour of the flax-epoxy composite on a range of 10 6-10 8 cycles. Results show that fatigue damage continues to evolve and the maximum stress continues to decrease as a function of increasing number of cycles, following a power-law trend. This result suggests that, if a fatigue limit does exist for unidirectional flax-epoxy composite laminates, it is so low that it cannot observed in tests up to 10 8 cycles. It is also recommended to take it into consideration when designing plant fibre composite structures.

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Section: Monotonic Tensile Behavioursupporting

confidence: 90%

About the fatigue endurance of unidirectional flax-epoxy composite laminates

Jeannin

Gabrion

Ramasso

et al. 2019

Composites Part B: Engineering

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“…In the next step, the airfoil skin was designed to bear the torsional loads, which were calculated in equation (6). Additionally, the stiffness was designed under the constraint θ max < 10°, and calculated in equation 7.…”

Section: Design and Methodologymentioning

confidence: 99%

“…A critical design requirement using flax was determined from tensile tests [6][7][8], which showed that flax fibers deform non-linearly under tensile load, especially cross-ply laminates. As the safe load should be bearable without plastic deformation, which is the beginning non-linear behavior was implemented by the identified "yield" points and the Hashin criterion, described in more detail in [6]. Whereas the ultimate load is allowed to cause plastic deformation, the maximum strain criterion was therefore applied for this demand.…”

Section: Design and Methodologymentioning

confidence: 99%

“…The analytical and numerical results of the design were validated and iteratively supported by experimental tests. Firstly, the plain flax and plain carbon material was characterized with tensile tests of 0°, 90°, and ±45°laminates using the DIC method ARAMIS [6]. Next, the sandwich lay-up of [±45 F,4 /0 B ] S was validated in a flexural test, as well as the whole carbon-flax-balsa spar.…”

Section: Fig 2 Tail Plane Section Cut and Materials Stack-ups At Varimentioning

confidence: 99%

“…Missing characteristics, such as shear and poisson's ratio in transversal direction were estimated from conventional laminates. A detailed description of the flax tensile tests is published in [6], including a bilinear modeling approach. A summary of the flax composite's elastic properties is listed in Table 1, strength and strain properties are listed in Table 2.…”

Section: A Static Tests On Elasticity and Failurementioning

confidence: 99%

See 2 more Smart Citations

An Eco-Efficient Helicopter Tailplane Hybridized from Flax, Balsa and Carbon

Strohrmann

Hajek

2019

AIAA Scitech 2019 Forum

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A tailplane for an ultralight helicopter was redesigned with the goal of using bio-based materials in a high proportion. Structural requirements were set to the national ultralight certification standards and were also adapted from the performance of the initial design tailplane, which was made of carbon prepreg materials and a foam core. In order to pursue this goal, pre-impregnated flax fiber composites, in combination with a balsa wood core and a small proportion of carbon fiber reinforcements, were used to design a new tailplane. A finite element model was developed, fed by material data from tensile tests and evolving iteratively from coupon and sub-component bending tests. Finally, a 450 mm section of the resulting design was built and a bio-based mass content of approximately 55 % was achieved. The new, hybrid version was analyzed experimentally in terms of weight, stiffness, strength/ failure, damping, and embodied energy, where benchmark data was obtained from either the reference tailplane or the certification specifications. Benefits of the new design were identified in a 2-8 times higher damping ratio, 65% less embodied energy (76.90 MJ kg −1), and reduced carbon footprint (5 kg kg −1), while weight, stiffness, and strength were performing in a sufficient and comparative manner as the reference.

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