Effect of polymer foam anisotropy on energy absorption during combined shear-compression loading

Mosleh, Yasmine; Bosche, Kelly Vanden; Depreitere, Bart; Sloten, Jos Vander; Verpoest, Ignaas; Ivens, Jan

doi:10.1177/0021955x17720156

Cited by 31 publications

(22 citation statements)

References 20 publications

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“…The combined shear‐compression set‐up comprises of two independent displacement actuators which apply simultaneous shear and compressive displacements in two orthogonal axes resulting in combined shear and compressive loading of the foam specimens. This set‐up was extensively described in our previous paper . The biaxial shear‐compression tests are performed at deformation angle of 45° meaning that both shear and compressive displacement rates were set at 2 mm min −1 .…”

Section: Methodsmentioning

confidence: 99%

Optimization of Composite Foam Concept for Protective Helmets to Mitigate Rotational Acceleration of the Head in Oblique Impacts: A Parametric Study

Mosleh¹,

Pastrav

Vuure³

et al. 2017

Adv Eng Mater

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Rotational acceleration of the head is known to be the cause of traumatic brain injuries. It was hypothesized that by introducing anisotropy in a foam liner in head protection applications, for example, protective helmets, rotational acceleration transmitted to the head can be further mitigated. Therefore, composite foam with a cylinder/matrix configuration with anisotropy at "macro level" is proposed as a smart structural solution to replace single layer foam headliners of the same weight and thickness. In this paper, a parametric study on the cylinder/matrix configuration is performed and the results are compared with these of single layer expanded polystyrene foam. The structure is subsequently optimized for the best performance in mitigation of rotational acceleration and velocity. Oblique impact results show that the parameters such as the number of cylinders in a given structure, and the compliance of the matrix foam significantly affect the extent of rotational acceleration and velocity mitigation. Optimized composite foam configurations are subsequently proposed and they demonstrate a mitigation of rotational acceleration and velocity up to 44 and 19%, respectively. Moreover, relevant global head injury criteria such as HIC (Head Injury Criterion), RIC (Rotational Injury Criterion), HIP max (Head Impact Power), GAMBIT (Generalised Acceleration Model for Brain Injury Threshold), and BrIC (Brain Injury Criterion) demonstrated reduction up to 27, 67, 31, 26, and 19%, respectively.

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Section: Methodsmentioning

confidence: 99%

Optimization of Composite Foam Concept for Protective Helmets to Mitigate Rotational Acceleration of the Head in Oblique Impacts: A Parametric Study

Mosleh¹,

Pastrav

Vuure³

et al. 2017

Adv Eng Mater

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“…A limitation of the present FE model is the modelling of the shear behaviour of the foam core. Mosleh et al [8] concluded that characterisation of cellular materials under multi-axial loading is necessary for the use of realistic and complex failure criteria in structural design, taking into account multiple loading directions. Lei et al [29] found that the shear modulus of the foam was also al.…”

Section: Results Of Hexapod Impact Tests On Kevlar-rohacell Sandwich mentioning

confidence: 99%

“…Instead, the structures are more frequently loaded at some oblique angle or complex trajectory such as collision with floating or submerged objects and low-speed berthing impacts [6] or lateral collisions in bridge [7]. The investigation of behaviour of sandwich composite to dynamic multi-axial loading is of great importance as in-service loading conditions are often multi-axial due to the complex geometries of structures and intricate loading conditions [8].…”

Section: Introductionmentioning

confidence: 99%

A new method for the study of parabolic impact of foam-core sandwich panels

Ramakrishnan

Guérard

Mahéo

et al. 2019

Composites Part B: Engineering

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Lightweight sandwich panels with composite facesheets and foam core have high impact energy absorption capability and are widely employed in multifunctional applications such as aircraft and marine structures. The dynamic behaviour of sandwich panels is typically studied for impact loading at normal angle of incidence but the structures are more frequently loaded at some oblique angle or with a complex tri-dimensional trajectory in real engineering situations. The damage area and damage modes for these trajectories are significantly different and it is not sufficient to study only normal impacts. There are well established experimental protocols for normal or oblique impact tests using devices like the drop tower, but impacts with complex trajectory are difficult to characterise experimentally. In this paper, a Gough-Stewart platform with six degrees of freedom has been modified to develop an original tri-dimensional impact device called Hexapod. The trajectory is defined to an impactor attached to the seventh jack of the Hexapod to study the response of sandwich plates to impact loading with complex trajectories. The applicability of the newly developed device is demonstrated by studying parabolic impact with different trajectories on sandwich plates with Kevlar facesheets and Rohacell foam core. The time history of vertical and horizontal components of force is measured using tri-axial load cell and strain history is obtained from Digital Image Correlation of a high speed camera images. The results of the parabolic impact show the importance of shear behaviour of the foam in the progression of damage in the sandwich panels. Additionally, the response of the sandwich panels to parabolic impact was simulated numerically using explicit finite element code LS-DYNA. The results of the FE model are compared with experimental data in terms of the force history and strain contours.

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“…water blown free rise polyurethane foams) can have highly anisotropic void shapes. The ellipsoidal shape of the voids formed during foaming has been found to greatly influence the material's stiffness during various loading types like tensile [34,35], compression [36,37], and impact loading [38]. With respect to mode I fracture, the influence of void anisotropy has been investigated for ductile materials [39] and cases where the crack tip is located in the void, for infinite materials [40].…”

Section: Effects Of Manufacturing Inaccuracies On the Stress Intensitmentioning

confidence: 99%

Experimental and numerical analysis of size effects on stress intensity in anisotropic porous materials

Touliatou

Wheel

2019

Engineering Failure Analysis

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A prominent size effect has previously been reported for the fracture behaviour of brittle porous materials, with smaller specimens behaving quite differently to their larger counterparts. In such materials, the size of the K-dominant zone has been numerically found to be greatly affected by the presence of voids in the near-tip area, thus putting the assumption of a single fracture parameter under question. In order to address this, in this study mode I tests are conducted on porous double cantilever beam specimens, while the stress distribution in the near-tip area is being observed by means of photoelasticity. Results validate the predicted size effect and suggest that the voids can indeed alter the size and shape of the stress pattern in the specimens. A parametric study is then conducted to investigate the influence of void shape variations that can be caused by manufacturing inaccuracies on the stress concentration at the crack tip. It is found that although the stress intensity at the crack tip can be greatly affected by such factors, the size of the K-dominant zone remains unaffected.

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Effect of polymer foam anisotropy on energy absorption during combined shear-compression loading

Cited by 31 publications

References 20 publications

Optimization of Composite Foam Concept for Protective Helmets to Mitigate Rotational Acceleration of the Head in Oblique Impacts: A Parametric Study

Optimization of Composite Foam Concept for Protective Helmets to Mitigate Rotational Acceleration of the Head in Oblique Impacts: A Parametric Study

A new method for the study of parabolic impact of foam-core sandwich panels

Experimental and numerical analysis of size effects on stress intensity in anisotropic porous materials

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