Experimental study on effect of loading rate on mode I delamination of z-pin reinforced laminates

This paper presents an experimental investigation on mode I delamination of z-pinned double-cantilever-beams (DCB) and associate z-pin bridging mechanisms. Tests were performed with three types of samples: big-pin with an areal density of 2%, small-pin with an areal density of 2% and small-pin with an areal density of 0.5%. The loading rates for each type of samples were set at 1 mm/min and 100 mm/min. Comparison of fracture load under different loading rates shows the rate effects on delamination crack opening and delamination growth. Optical micrographs of z-pins after pullout were also presented to identify the bridging mechanisms of z-pins under different loading rates.

Polyethylene terephthalate (PET) bulk film analysis using C60+, Au3+, and Au+ primary ion beams

The damage characteristics of polyethylene terephthalate (PET) have been studied under bombardment by C₆₀+, Au₃+ and Au+ primary ions. The observed damage cross-sections for the three ion beams are not dramatically different. The secondary ion yields however were significantly enhanced by the polyatomic primary ions where the secondary ion yield of the [M + H]+ is on average 5× higher for C₆₀+ than Au₃+ and 8× higher for Au₃+ than Au+. Damage accumulates under Au+ and Au₃+ bombardment while C₆₀+ bombardment shows a lack of damage accumulation throughout the depth profile of the PET thick film up to an ion dose of 1 ~ 10¹⁵ ions cm⁻². These properties of C₆₀+ bombardment suggest that the primary ion will be a useful molecular depth profiling tool.

Improving bond strength for CFRP-RC beams interface

 Strengthened concrete structures using advanced materials such as CFRP composites has been proved an efficient technique. The bonding agent (epoxy resin) used to bond the CFRP composites with the concrete structures is the main parameter that contributes to premature failure. I was able to recommend to a new modified epoxy resin to enhance the general behavior of the strengthened concrete structure with respect to durability and ductility.