Mohamad Zaki Hassan

Strain rate effects in the indentation behavior of foam-based sandwich structures:

Indentation tests have been undertaken at quasi-static and impact rates of strain on sandwich structures based on six different types of polymer foam core and two types of composite skin. Initially, the influence of strain rate on the compression properties of the sandwich structures has been investigated, where it has been shown that the plastic collapse strength of the foam cores is rate sensitive, increasing by approximately 100% over the range of strain rates considered. The indentation behavior of the sandwich structures was characterized using a Meyer indentation law of the form P = Cαn, where P is the applied force, α is the resulting indentation, and C, the contact stiffness and n, the indentation exponent, are constants for a given system. It has been shown that the value of the exponent, n, does not vary significantly with the properties of the core or the skin, typically being close to unity for all tests. The contact stiffness C varied greatly and was found to depend on the plastic collapse strength of the foam and the properties of the skin. It has been shown that a plot of C vs. plastic collapse strength containing all of the quasi-static and dynamic data appears to yield a unique relationship for the systems considered here. Tests have also shown that C varies with indentor radius, with the greatest sensitivity to indentor radius being observed in the higher modulus foams. These results highlight the importance of using the appropriate dynamic contact properties when modeling the impact response of foam-based sandwich structures.

The impact response of environmental-friendly sandwich structures

The low-velocity impact response of sandwich structures based on fully-recyclable skin and core materials has been investigated. Particular attention has been focused on structures based on self-reinforced polypropylene skins combined with a polypropylene honeycomb core. Two types of skin designs were considered, the first being based on a single ‘as-supplied’ monolithic self-reinforced polypropylene laminate and the second being manufactured from thin self-reinforced polypropylene sheets bonded together using a hot-melt polypropylene film. For comparative purposes, a limited number of tests have also been carried out on a more conventional GFRP/aluminium honeycomb sandwich structure. Drop-weight impact test have shown that all-polypropylene honeycomb sandwich structures absorb significant energy through plastic deformation in the composite skins as well as plastic buckling in the honeycomb core. It has also been shown that the design of the self-reinforced polypropylene skin has a significant effect on the energy-absorbing characteristics of the sandwich structure, with the performance of systems based on multiple layer skins greatly exceeding that observed following tests on a monolithic design. Tests on plain laminates also yielded similar conclusions, with multilayer systems offering much higher perforation resistances than their plain counterparts. Finally, it has been demonstrated that when the impact data are normalised by their respective areal densities, the all-polypropylene composites significantly out-perform GFRP/aluminium honeycomb sandwich structures.

Seawater infiltration effect on thermal degradation of fiber reinforced epoxy composites

Seawater salinity has been associated with the reduction of polymer structure durability. The aim of this study is to investigate the change in thermal degradation of fiber reinforced epoxy composite due to the presence of seawater. Carbon fiber, carbon/kevlar, fiberglass, and jute that reinforced with epoxy resin was laminated through hand-layup technique. Initially, these specimen was sectioned to 5×5 mm dimension, then immersed in seawater and distilled water at room temperature until it has thoroughly saturated. Following, the thermal degradation analysis using Differential Scanning Calorimetry (DSC), the thermic changes due to seawater infiltration was defined. The finding shows that moisture absorption reduces the glass transition temperature (Tg) of fiber reinforced epoxy composite. However, the glass transition temperature (Tg) of seawater infiltrated laminate composite is compareable with distilled water infiltrated laminate composite. The carbon fiber reinfored epoxy has the highest glass transi...

Mechanical behavior of Kenaf/Epoxy corrugated sandwich structures

This study presents the response of kenaf/epoxy corrugated sandwich structure during quasi-static test. Force-displacements curves have been deducted to determine the deformation pattern and collapse behavior of the structure. Kenaf/epoxy sandwich structures skins fabricated by using hand layup technique and the corrugated core were moulded by using steel mould. Different thicknesses of corrugated core web with two sizes of kenaf fibers were used. The corrugated core is then bonded with the skins by using poly-epoxy resin and has been cut into different number of cells. The specimens then tested under tensile and compression at different constant speeds until the specimens fully crushed. Tensile tests data showed the structure can be considered brittle when it breaking point strain, e less than 0.025. In compression test, the specimens fail due to dominated by stress concentration that initiated by prior cracks. Also, the specimens with more number of cells and thicker core web have higher strength and the ability to absorb higher energy.

Energy management strategies at emergency department block C Hospital Sungai Buloh, Malaysia

Energy is an important element in human daily life. In Malaysia, about 80% of electrical energy produced from burning fuels that will cause of carbon dioxide emission to atmosphere. The effect could be reduced with less energy consumption. This project focuses on energy management strategies for energy saving that can be done on the HVAC system, air-cond, lighting and office equipment in Emergency Department, Block C Hospital Sungai Buloh. The annual profit, total cost and payment period for each research method are also studied. To implement for all major system must be link to chapter by Buiding Automation System. Major studies for this topic is to implement energy saving, calculate energy comsumption, power, area specific room, return of investment, analysis for daily cost for used, total for kWh for monthly usage.