Reliable line production processes and simulation tools play a central role for the structural integration of thermoplastic composites in advanced lightweight constructions. Provided that material-adapted joining tech...Reliable line production processes and simulation tools play a central role for the structural integration of thermoplastic composites in advanced lightweight constructions. Provided that material-adapted joining technologies are available, they can be applied in heavy-duty multi-material designs (MMD). A load-adapted approach was implemented into the new fully automatic and fault-tolerant thermo mechanical flow drill joining (FDJ) concept. With this method it is possible to manufacture reproducible high strength FRP/metal-joints within short cycle times and without use of extra joining elements for the first time. The analysis of FDJ joints requires a simplified model of the joint to enable efficient numerical simulations. The present work introduces a strategy in modeling a finite-element based analogous-approach for FDJ-joints with glass fiber reinforced polypropylene and high-strength steel. Combined with a newly developed section-force related failure criterion, it is possible to predict the fundamental failure behavior in multi-axial stress states. The functionality of the holistic approach is illustrated by a demonstrator that represents a part of a car body-in-white structure. The comparison of simulated and experimentally determined failure loads proves the applicability for several combined load cases.展开更多
This paper introduces an efficient holistic approach to the design optimization of lightweight structures of braided fiber-reinforced plastic material. The approach aims to mitigate the paradox of making design decisi...This paper introduces an efficient holistic approach to the design optimization of lightweight structures of braided fiber-reinforced plastic material. The approach aims to mitigate the paradox of making design decisions at early development phases, when necessary information is incomplete or lacking detail so as to properly make these decisions. However, expert knowledge is available and though it is imprecise in nature, it can compensate to create useful models. Manufacturing effort for the braiding process has been described by information accumulated via interviews with braiding experts. This information is then modelled using the soft-computing approach by fuzzy-rule-based systems. The resulting models can further be efficiently integrated into the structural design optimization process. A multidisciplinary design optimization is facilitated considering several aspects including manufacturing effort and structural mechanics, which can be used in early design phases leading to more holistic designing and, thereby, unlocking lightweight and cost-reducing potentials. Benefits of this method, including viability and ease of implementation, are proven by investigations on two academic test problems before advancing to the challenging automotive engineering design problem of the roadster A-pillar.展开更多
A new constructive and technological approach was developed for the efficient production of large-dimensioned, curved freeform formworks, which allow the manufacturing of single and double-curved textile reinforced co...A new constructive and technological approach was developed for the efficient production of large-dimensioned, curved freeform formworks, which allow the manufacturing of single and double-curved textile reinforced concrete elements. The approach is based on a flexible, multi-layered formwork system, which consists of glass-fibre reinforced plastic (GFRP). Using the unusual structural behavior caused by anisotropy, these GFRP formwork elements permit a specific adjustment of defined curvature. The system design of the developed GFRP formwork and the concrete-lightweight-elements with stabilized spacer fabric was examined exhaustively. Prototypical curved freeform surfaces with different curvature radii were designed, numerically computed and produced. Furthermore, the fabric’s contour accuracy of the fabric was verified, and its integration was adjusted to loads.展开更多
This paper presents the development and technological implementation of textile reinforced concrete (TRC) shells with integrated functions, such as illumination and light control. In that regard the establishment of m...This paper presents the development and technological implementation of textile reinforced concrete (TRC) shells with integrated functions, such as illumination and light control. In that regard the establishment of material, structural and technological foundations along the entire value chain are of central importance: From the light-weight design idea to the demonstrator and reference object, to the technological implementation for the transfer of the research results into practice. The development of the material included the requirement-oriented composition of a high-strength fine grained concrete with an integrated textile reinforcement, such as carbon knitted fabrics. Innovations in formwork solutions provide new possibilities for concrete constructions. So, a bionic optimized shape of the pavilion was developed, realized by four connected TRC-lightweight-shells. The thin-walled TRC-shells were manufactured with a formwork made of glass-fibre reinforced polymer (GFRP). An advantage of the GFRP-formwork is the freedom of design concerning the formwork shape. Moreover, an excellent concrete quality can be achieved, while the production of the precast concrete components is simple and efficient simultaneously. After the production the new TRC-shells were installed and assembled on the campus of TU-Chemnitz. A special feature of the research pavilions are the LED light strips integrated in the shell elements, providing homogeneous illumination.展开更多
This paper reports the development of an Alkali Activated Binder (AAB) with an emphasis on the performance and the durability of the AAB-matrix. For the development of the matrix, the reactive components granulated sl...This paper reports the development of an Alkali Activated Binder (AAB) with an emphasis on the performance and the durability of the AAB-matrix. For the development of the matrix, the reactive components granulated slag and coal fly ash were used, which were alkali activated with a mixture of sodium hydroxide (2 - 10 mol/l) and aqueous sodium silicate solution (SiO<sub>2</sub>/Na<sub>2</sub>O molar ratio: 2.1) at ambient temperature. A sodium hydroxide concentration of 5.5 mol/l revealed the best compromise between setting time and mechanical strengths of the AAB. With this sodium hydroxide concentration, the compressive and the 3-point bending tensile strength of the hardened AAB were 53.4 and 5.5 MPa respectively after 14 days. As a result of the investigation of the acid resistance, the AAB-matrix showed a very high acid resistance in comparison to ordinary Portland cement concrete. In addition, the AAB had a high frost resistance, which had been validated by the capillary suction, internal damage and freeze thaw test with a relative dynamic E-Modulus of 93% and a total amount of scaled material of 30 g/m<sup>2</sup> after 28 freeze-thaw cycles (exposure class: XF3).展开更多
文摘Reliable line production processes and simulation tools play a central role for the structural integration of thermoplastic composites in advanced lightweight constructions. Provided that material-adapted joining technologies are available, they can be applied in heavy-duty multi-material designs (MMD). A load-adapted approach was implemented into the new fully automatic and fault-tolerant thermo mechanical flow drill joining (FDJ) concept. With this method it is possible to manufacture reproducible high strength FRP/metal-joints within short cycle times and without use of extra joining elements for the first time. The analysis of FDJ joints requires a simplified model of the joint to enable efficient numerical simulations. The present work introduces a strategy in modeling a finite-element based analogous-approach for FDJ-joints with glass fiber reinforced polypropylene and high-strength steel. Combined with a newly developed section-force related failure criterion, it is possible to predict the fundamental failure behavior in multi-axial stress states. The functionality of the holistic approach is illustrated by a demonstrator that represents a part of a car body-in-white structure. The comparison of simulated and experimentally determined failure loads proves the applicability for several combined load cases.
文摘This paper introduces an efficient holistic approach to the design optimization of lightweight structures of braided fiber-reinforced plastic material. The approach aims to mitigate the paradox of making design decisions at early development phases, when necessary information is incomplete or lacking detail so as to properly make these decisions. However, expert knowledge is available and though it is imprecise in nature, it can compensate to create useful models. Manufacturing effort for the braiding process has been described by information accumulated via interviews with braiding experts. This information is then modelled using the soft-computing approach by fuzzy-rule-based systems. The resulting models can further be efficiently integrated into the structural design optimization process. A multidisciplinary design optimization is facilitated considering several aspects including manufacturing effort and structural mechanics, which can be used in early design phases leading to more holistic designing and, thereby, unlocking lightweight and cost-reducing potentials. Benefits of this method, including viability and ease of implementation, are proven by investigations on two academic test problems before advancing to the challenging automotive engineering design problem of the roadster A-pillar.
基金supported by the Priority Program SPP 1542 of the German Research Foundation(DFG)
文摘A new constructive and technological approach was developed for the efficient production of large-dimensioned, curved freeform formworks, which allow the manufacturing of single and double-curved textile reinforced concrete elements. The approach is based on a flexible, multi-layered formwork system, which consists of glass-fibre reinforced plastic (GFRP). Using the unusual structural behavior caused by anisotropy, these GFRP formwork elements permit a specific adjustment of defined curvature. The system design of the developed GFRP formwork and the concrete-lightweight-elements with stabilized spacer fabric was examined exhaustively. Prototypical curved freeform surfaces with different curvature radii were designed, numerically computed and produced. Furthermore, the fabric’s contour accuracy of the fabric was verified, and its integration was adjusted to loads.
文摘This paper presents the development and technological implementation of textile reinforced concrete (TRC) shells with integrated functions, such as illumination and light control. In that regard the establishment of material, structural and technological foundations along the entire value chain are of central importance: From the light-weight design idea to the demonstrator and reference object, to the technological implementation for the transfer of the research results into practice. The development of the material included the requirement-oriented composition of a high-strength fine grained concrete with an integrated textile reinforcement, such as carbon knitted fabrics. Innovations in formwork solutions provide new possibilities for concrete constructions. So, a bionic optimized shape of the pavilion was developed, realized by four connected TRC-lightweight-shells. The thin-walled TRC-shells were manufactured with a formwork made of glass-fibre reinforced polymer (GFRP). An advantage of the GFRP-formwork is the freedom of design concerning the formwork shape. Moreover, an excellent concrete quality can be achieved, while the production of the precast concrete components is simple and efficient simultaneously. After the production the new TRC-shells were installed and assembled on the campus of TU-Chemnitz. A special feature of the research pavilions are the LED light strips integrated in the shell elements, providing homogeneous illumination.
文摘This paper reports the development of an Alkali Activated Binder (AAB) with an emphasis on the performance and the durability of the AAB-matrix. For the development of the matrix, the reactive components granulated slag and coal fly ash were used, which were alkali activated with a mixture of sodium hydroxide (2 - 10 mol/l) and aqueous sodium silicate solution (SiO<sub>2</sub>/Na<sub>2</sub>O molar ratio: 2.1) at ambient temperature. A sodium hydroxide concentration of 5.5 mol/l revealed the best compromise between setting time and mechanical strengths of the AAB. With this sodium hydroxide concentration, the compressive and the 3-point bending tensile strength of the hardened AAB were 53.4 and 5.5 MPa respectively after 14 days. As a result of the investigation of the acid resistance, the AAB-matrix showed a very high acid resistance in comparison to ordinary Portland cement concrete. In addition, the AAB had a high frost resistance, which had been validated by the capillary suction, internal damage and freeze thaw test with a relative dynamic E-Modulus of 93% and a total amount of scaled material of 30 g/m<sup>2</sup> after 28 freeze-thaw cycles (exposure class: XF3).
