Fibrous Morphologies

Living organisms have evolved effective structural solutions in response to the inherent constraints of their respective environments through a process of morphological adaptation. Given the fact that the majority of natural load bearing materials are fibrous composites, the authors suggest the analysis of appropriate biological role models as a promising strategy for informing the application of fibre reinforced polymers (FRP) in architecture. In this paper the authors present a biomimetic design methodology for seamless large-scale FRP structures involving the analysis of the exoskeletons of Arthropoda with regards to structural performance criteria, the development of a custom robotic filament winding process, and the translation of biological and fabricational principles into the architectural domain through physical prototyping and the development of custom digital tools. The resulting performative material system is evaluated in a full-scale research pavilion

Investigation of geometrical and composite material parameters for tension-absorbing bolted joints

In the event of an aircraft crash landing, the fuselage cross-section tends to ovalise. This leads to tension loading of the passenger and cargo floor cross-beams. In past research activities, this has been identified as an opportunity to absorb energy, through a novel design of the frame to cross-beam attachments [1]. These specialised attachments are referred to as tension-absorbing joints. They are designed to protect the bolt from early failure and provide guidance for it to push through, and crush, the composite adherends over a considerable distance, leading to a substantial amount of energy absorption. In the present work, material and geometrical parameters of these joints are investigated experimentally to provide data for a design database. A simplified version of the joint is tested, in which a pin is pulled through a 2 mm thick composite laminate using a specialised experimental rig. The bearing strength and energy absorption capabilities are investigated under quasi-static loading, for 4 mm and 12 mm diameter pins and three different stacking sequences. Two different specimen widths are employed to determine the extent of damage progression towards the specimen edge. Digital Image Correlation (DIC) is used to measure the pin displacement. It is found that symmetric layups with a repeating unit of [45/ 45/90/0] inhibit off-axis pin movement, providing for a consistent test, and that the wider specimen is required to avoid the damage reaching all the way to the specimen edge. For both pin diameters, an interspersed stacking sequence results in higher values of peak load, mean crushing load and specific energy absorption than a blocked layu

Effects of transient dynamic loading on the energy absorption capability of composite bolted joints undergoing extended bearing failure

Carbon fibre reinforced polymer (CFRP) materials are widely used in transport aircraft. Crashworthiness requirements demand sufficient energy absorption capacity, especially in the fuselage structure. In a recently-proposed approach, specifically-designed tension absorber joints utilize tension loads for energy absorption via progressive bearing failure. For further development of the concept, experimental tests are performed on pin- joints in quasi-isotropic CFRP material, under transient dynamic loading at 3 m/s. Investigated parameters are laminate thickness, stacking sequence and pin diameter, and the results are evaluated using the performance parameters ultimate bearing strength, mean crush stress and mass-specific energy absorption. A strong relation between the ratio of pin diameter to laminate thickness, D/t, and the performance parameters is found. Compared to previous results for quasi-static loading, the ultimate bearing strength is increased whereas the mean crush stress and mass-specific energy absorption are reduced. Digital image correlation and computed tomography analysis reveals the mechanisms behind the observed trends. The results provide a basis for further optimization of energy-absorbing joints and validation of finite element models

Effects of transient dynamic loading on the energy absorption capability of composite bolted joints undergoing extended bearing failure

The full text of this article will not be available in ULIR until the embargo expires on the 21/05/2022Carbon fibre reinforced polymer (CFRP) materials are widely used in transport aircraft. Crashworthiness requirements demand sufficient energy absorption capacity, especially in the fuselage structure. In a recently-proposed approach, specifically-designed “tension absorber” joints utilize tension loads for energy absorption via progressive bearing failure. For further development of the concept, experimental tests are performed on pin- joints in quasi-isotropic CFRP material, under transient dynamic loading at 3 m/s. Investigated parameters are laminate thickness, stacking sequence and pin diameter, and the results are evaluated using the performance parameters ultimate bearing strength, mean crush stress and mass-specific energy absorption. A strong relation between the ratio of pin diameter to laminate thickness, D/t, and the performance parameters is found. Compared to previous results for quasi-static loading, the ultimate bearing strength is increased whereas the mean crush stress and mass-specific energy absorption are reduced. Digital image correlation and computed tomography analysis reveals the mechanisms behind the observed trends. The results provide a basis for further optimization of energy-absorbing joints and validation of finite element models