Introduction Mechanical Properties Analysis Folded Textured Sheets ...
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Introduction In engineering, shell structures are structures where the mate- rial thickness is very small compared to the structure’s overall dimensions. Their use is widespread, and ranges from plastic drinks bottles, to aircraft fuselages and building façades. A novel application of shell structures is in morphing struc- tures, which are designed to alter their global shape to meet new requirements. Existing materials cannot provide the nec- essary mechanical properties for these applications; paradoxi- cally, the material needs to be stiff in certain, but flexible in other deformation modes. In our research we aim to develop novel materials for these morphing shell structures, using folded textured sheets. Mechanical Properties The folded sheets possess novel and very interesting mechan- ical properties. The folds allow relatively large global deforma- tions of the sheets, whilst still providing improved bending stiff- ness. Furthermore, the folds enable the sheets to be deformed into configurations unobtainable with regular shells: folded sheets with an initially zero global Gaussian curvature (i.e. a globally flat sheet) can be transformed into saddle-shaped or spherical configurations (respectively a negative or positive Gaussian curvature). Folded Shell Structures Figure 2 - an example folded textured , the Miura sheet. Figure 4 - the saddle-shaped deformation mode of the pin-jointed framework model. Analysis In order to understand their mechanical behaviour, the folded sheets are modelled as pin-jointed frameworks, with addition- al bending stiffness along the fold lines and across the facets. The eigenmodes of the associated tangent stiffness matrix then provide insight in the global deformation kinematics of the sheet. In ongoing work we are trying to capture the unique be- haviour of the sheets in an equivalent continuum mechanics model. Folded Textured Sheets The core idea of our research is to impart new mechanical properties to thin-walled sheets by introducing a local texture (such as corrugations, dimples, folds, etc.) that affects the glo- bal mechanical properties. Our specific area of interest is us- ing tessellated folding patterns, inspired by the Japanese art of Origami folding, to introduce the new mechanical properties. Figure 3 - the Miura sheet can easily be bent or twisted into a saddle-shaped configuration. Conclusions By introducing a folded texture pattern to thin sheets, a nov- el ‘sheet material’ has been created, with unique mechanical properties. Their combination of flexibility in some, and rigid- ity in other deformation modes, makes these folded textured sheets very suitable for use in morphing structures. Addition- ally, these novel folded textured sheets may also find applica- tions in architecture or micromechanical systems. Mark Schenk ([email protected]) & Dr Simon Guest Advanced Structures Group, Cambridge University Engineering Department 1 2 3 4 5 Figure 1 - inspired by the way birds adapt their wings during flight, morphing aircraft wings are an active area of research and provide a potential application for folded textured sheets. Advanced Structures Group Laboratory © MMIX - MS
Transcript of Introduction Mechanical Properties Analysis Folded Textured Sheets ...
Introduction In engineering, shell structures are structures where the mate-rial thickness is very small compared to the structure’s overall dimensions. Their use is widespread, and ranges from plastic drinks bottles, to aircraft fuselages and building façades. A novel application of shell structures is in morphing struc-tures, which are designed to alter their global shape to meet new requirements. Existing materials cannot provide the nec-essary mechanical properties for these applications; paradoxi-cally, the material needs to be stiff in certain, but flexible in other deformation modes. In our research we aim to develop novel materials for these morphing shell structures, using folded textured sheets.
Mechanical PropertiesThe folded sheets possess novel and very interesting mechan-ical properties. The folds allow relatively large global deforma-tions of the sheets, whilst still providing improved bending stiff-ness. Furthermore, the folds enable the sheets to be deformed into configurations unobtainable with regular shells: folded sheets with an initially zero global Gaussian curvature (i.e. a globally flat sheet) can be transformed into saddle-shaped or spherical configurations (respectively a negative or positive Gaussian curvature).
Folded Shell Structures
Figure 2 - an example folded textured , the Miura sheet.
Figure 4 - the saddle-shaped deformation mode of the pin-jointed framework model.
AnalysisIn order to understand their mechanical behaviour, the folded sheets are modelled as pin-jointed frameworks, with addition-al bending stiffness along the fold lines and across the facets. The eigenmodes of the associated tangent stiffness matrix then provide insight in the global deformation kinematics of the sheet. In ongoing work we are trying to capture the unique be-haviour of the sheets in an equivalent continuum mechanics model.
Folded Textured SheetsThe core idea of our research is to impart new mechanical properties to thin-walled sheets by introducing a local texture (such as corrugations, dimples, folds, etc.) that affects the glo-bal mechanical properties. Our specific area of interest is us-ing tessellated folding patterns, inspired by the Japanese art of Origami folding, to introduce the new mechanical properties.
Figure 3 - the Miura sheet can easily be bent or twisted into a saddle-shaped configuration.
ConclusionsBy introducing a folded texture pattern to thin sheets, a nov-el ‘sheet material’ has been created, with unique mechanical properties. Their combination of flexibility in some, and rigid-ity in other deformation modes, makes these folded textured sheets very suitable for use in morphing structures. Addition-ally, these novel folded textured sheets may also find applica-tions in architecture or micromechanical systems.
Mark Schenk ([email protected]) & Dr Simon Guest Advanced Structures Group, Cambridge University Engineering Department
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Figure 1 - inspired by the way birds adapt their wings during flight, morphing aircraft wings are an active area of research and provide a potential application for folded textured sheets.
Advanced Structures Group Laboratory
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