Key Engineering Materials Vols. 334-335

Abstract: The Timoshenko beam theory is used to model each part of cracked beam and to calculate the potential energy release rate. Calculations are given for the double cantilever beam specimen, which is simulated as two separate beams connected elastically along the uncracked interface.

Abstract: The effect of water absorption on the compressive strength after impact (CAI strength) and the post impact fatigue (PIF) properties of CFRP laminate were evaluated. Materials used were plain woven T300B-3K CFRP laminates and multi-axial knitted T700S-12K CFRP laminates molded by the vacuum assisted resin transfer molding (VARTM) method with vinylester as the matrix. Coupon specimens, which were applied the impact energy (1 J per unit thickness), were soaked in a water bath at 95oC for 120 hours up to the saturation water content of 0.6 wt%. CAI and PIF strengths of ‘Dry’ and ‘Wet’ specimens of plain woven CFRP showed almost same values. Thus, for T300B plain woven CFRP laminates, the effect of water absorption on PIF properties was small. On the other hand, multi-axial knitted CFRP laminates showed the large effect of water absorption, and Wet specimens showed lower PIF properties than Dry ones. However, net CAI and PIF strengths of multi-axial knitted CFRP were larger than that of plain woven CFRP.

Abstract: Feasibility study of partially replacement of cement and ground sand by ground steel slag (GSS) and ground granulated blast furnace slag (GGBFS) in producing prestressed high strength concrete pile (PHC) was conducted. The results showed that under normal curing（20oC, 95% RH）and the steam curing condition (80oC), GSS possessed less reactivity than GGBFS. However, under autoclave curing condition (180 °C, 1.0MPa), the reactivity of GSS can be effectively activated. The autoclaving strength of the concrete made from 20% GSS with Blaine 550m2/kg, 55% cement and 25% ground sand could reach 89.0 MPa which is not only higher than that of GGBFS (82.8MPa), but also higher than that of traditional PHC concrete (83.9Mpa, 70% cement and 30% ground sand). It’s feasible to produce PHC concrete by GSS with high fineness and optimized dosage.

Abstract: In the present work, thermal expansion coefficients of a number of ceramic coatings were studied by a non-destructive technique (NDT) known as shearography. Ceramic coatings, i.e., a white enamel and a yellow Acrylic Lacquer on a metallic alloy, i.e., carbon steels, were investigated at a temperature range simulating the severe weather temperatures in Kuwait, especially between the daylight and the night time temperatures, 20-60 0C. The investigation was focused on determining the in-plane displacement of the coating, which corresponds to the thermal deformation (strain), with respect to the applied temperature range. A mathematical relationship was derived along with the experimental data. The mathematical relationship described the thermal deformation of a coated film as a function of temperature. Furthermore, results of shearography indicate that the technique is found very useful NDT method not only for determining the thermal expansion coefficients of different coatings, but also the technique can be used as a 2D- microscope for monitoring the deformation of various coatings in at a submicroscopic scale.

Abstract: This report proposed the injection molding method of thermoplastic composite materials reinforced by the glass fiber extracted from FRP waste. Glass fiber was pre-treated by card machines and mixed with PP fiber. The sliver-type glass/PP mixture was fed into the injection molding machine directly. As a result, the glass fiber reinforced PP composites were obtained. The mechanical properties of the fiber reinforced composites were measured and discussed. It is concluded that the extracted glass fiber is good for the reinforcement of composite. The result suggests that the injection molding method described herein shows promise for contributing toward the material recycling of glass fiber extracted by the normal pressure dissolution method.

Abstract: Composite components made from vinyl ester resins by Centre of Excellence in Engineered Fiber Composites (CEEFC), University of Southern Queensland (USQ) suffer considerable shrinkage during hardening. Currently, CEEFC solves the shrinkage problem by breaking a large composite component into smaller composite parts because smaller parts tend to have less shrinkage. These smaller parts are then joined together to form the overall structure. The shrinkage of vinyl ester particulate composites has been reduced by curing the resins under microwave conditions. The reduction in the shrinkage of the resins by microwaves will enable the manufacture of large vinyl ester composite items possible. This project investigates the difference in impact strength, tensile strength and Young’s modulus of 33 percent by weight of fly-ash particulate reinforced vinyl ester composite, VE/FLY-ASH (33%) cured under microwave and ambient conditions. Drop weight impact tests were used to find out the impact strength of the composite, while tensile tests were used to find out the tensile strength and Young’s modulus of the composite. The power levels of microwaves used were 180 and 360 W; the duration of exposure of the composite samples to microwave irradiation varied from 20 to 50 seconds. The difference in impact strength and Young’s modulus between microwave cured vinyl ester particulate composites and those cured under ambient conditions had been found to be minimal. However, the tensile strength of the composite samples cured under microwave conditions can be higher than those cured under ambient conditions.

Abstract: CuW50Cr25 composite prepared by infiltration was investigated. The results show that the microstructure consists of four phases: W-rich and Cr-rich CuWCr solid solution as well as Cr-rich and Cu-rich CrCu phases. The original Cr particles in the compact are replaced part by Cu-rich CuCr phase and part by Cr-rich CrCu phase which is the first breakdown phase in the course of the material’s arcing. The chopping current value of CuW50Cr25 composite is 2.4A and arc duration is 4.01ms. These properties are much more excellent than counterpart of CuW70. The breakdown strength is 2.31×108 V/m and comparable with the CrCu contact materials.

Abstract: Although the autoclave technique produces composite parts of high quality, the process is time consuming and has intrinsically high capital and operating costs. QuickstepTM is a novel polymer composite manufacturing technique designed for the out-of-autoclave processing of highquality, low-cost components with a reduction in cure-cycle times. This paper assesses the use of the Quickstep method for the processing of an epoxy-carbon fibre aerospace composite material. The Quickstep process is compared both to a thermal vacuum-bag only process and the manufacturer’s specifications for autoclave cured panels. Higher process ramp rates, achievable by using Quickstep, have been shown to reduce resin viscosity and facilitate void removal. Through manipulation of the Quickstep cure cycle while the resin is at low viscosity, significant effects on the mechanical properties of the product are demonstrated. Using Quickstep curing it has been found that better interlaminar properties than the manufacturers autoclave data could be obtained while the flexural strength was a little lower. The work identifies key parameters associated with the Quickstep process giving an insight into how it can be optimised further in an attempt to produce panel properties that rival those produced by autoclave methods.