Su st ai na bl e M at er ia ls an d St ru ct ur al Sy st em s

Improvement of mechanical properties of light-weight corrugated core sandwich structures is a big demand in aerospace applications. Among these applications, space vehicles which encounter pressure loads and severe aerodynamic heating during ascent and reentry. The open-cell corrugated core is useful for active cooling of the sandwich structures. In this work, hybrid composite structural members with fiberglass corrugated core and carbon fiber skin facings were manufactured using vacuum bag technique. Different specimen configurations with rectangular cross-section area have been subjected to the load in the longitudinal direction of the corrugation and examined by edgewise compression test. The proposed testing has been applied to take advantage of the highest inertia of the specimen in such orientation. The test provides a basis for estimating the load carrying capacity when these structure members are used as individual webs in the aircraft interiors. Also as the core sheet is turned by 90° to the regular load direction, this structure member is similar to the so-called honeycomb when ordered in parallel rows and hence it is appropriate for floor sandwiching. In contrary to a honeycomb, this core consists of fiberglass laminate and therefore higher compressive resistance is associated. The results exhibit high values of both stiffness and ultimate compression force in the corrugation direction. For the rectangular area and the open corrugated contour, specific properties relative to the weight are extremely high. Also, the results and graphs indicate that there must be at least three corrugated ligaments with a trapezoidal cross section of 0.5” height and 63o per cell to grantee stability under load and high absorbed energy in the non-linear stage as well.

Lightweight sandwich structures are used in the aircraft industry because of their high strength-to-weight and stiffness-to-weight ratios. Structural components are often subjected to edge loads in compression or tension. The sandwich structure under the edge compression load exhibits excellent compression capacity. On the contrary of loading under flatwise compression, the sandwich under edge compression undergoes drastic tearing and fracture. The current study is based on experimental work on sandwich-structures made of carbon fiber and natural fiber reinforced face sheets with different core materials. The natural fiber (hemp) is highlighted in the current study to improve the fracture resistance of skins. The hemp-skin demonstrates comparable compression properties to those of carbon fiber under edge compressive load. The skin from hemp has great fracture resistance while the carbon one experienced dramatic fracture, tearing, and delamination. This outcome of the current study, in addition to the lightweight, lowcost ease handling, simple manufacturing, and eco-friendship make the hemp a competitive industrial material in aerospace applications. More details about the manufacturing and the failure modes are discussed as well.

Earthquakes threaten humanity globally in complex ways that mainly include various socioeconomic consequences of life and property losses. Resilience against seismic risks is of high importance in the modern world and needs to be sustainable. Sustainable earthquake resilience (SER) from the perspective of structural engineering means equipping the built environment with appropriate aseismic systems. Shape memory alloys (SMAs) are a class of advanced materials well suited for fulfilling the SER demand of the built environment. This article explores how this capability can be realized by the innovative SMA-based superelasticity-assisted slider (SSS), recently proposed for next-generation seismic protection of structures. The versatility of SSS is first discussed as a critical advantage for an effective SER. Alternative configurations and implementation styles of the system are presented, and other advantageous features of this high-tech isolation system (IS) are studied. Results of shaking table experiments, focused on investigating the expected usefulness of SSS for seismic protection in hospitals and conducted at the structural earthquake engineering laboratory of the University of Bonab, are then reported. SSS is compared with currently used ISs, and it is shown that SSS provides the required SER for the built environments and outperforms other ISs by benefitting from the pioneered utilization of SMAs in a novel approach.

Su st ai na bl e M at er ia ls an d St ru ct ur al Sy st em s