Steven Eric Zeltmann

Data characterizing tensile behavior of cenosphere/HDPE syntactic foam

The data set presented is related to the tensile behavior of cenosphere reinforced high density polyethylene syntactic foam composites “Processing of cenosphere/HDPE syntactic foams using an industrial scale polymer injection molding machine” (Bharath et al., 2016) [1]. The focus of the work is on determining the feasibility of using an industrial scale polymer injection molding (PIM) machine for fabricating syntactic foams. The fabricated syntactic foams are investigated for microstructure and tensile properties. The data presented in this article is related to optimization of the PIM process for syntactic foam manufacture, equations and procedures to develop theoretical estimates for properties of cenospheres, and microstructure of syntactic foams before and after failure. Included dataset contains values obtained from the theoretical model.

Thermal expansion and dynamic mechanical analysis of epoxy matrix–borosilicate glass hollow particle syntactic foams

Syntactic foams are commonly fabricated with sodalime–borosilicate glass hollow microsphere fillers, which are susceptible to degradation after long-term or high temperature moisture exposure. In comparison, borosilicate glass hollow particles offer higher degradation resistance to moisture, lower thermal expansion, and higher softening temperature. This work explores borosilicate glass hollow microspheres for use as fillers in syntactic foams and studies their thermophysical properties. The coefficient of thermal expansion over the temperature range 35–90℃ was observed to decrease from 62.4 μ/K for the matrix resin to a minimum of 24.3 μ/K for syntactic foams, representing higher thermophysical stability of syntactic foams. Theoretical models are used to conduct parametric studies and understand the correlation between material parameters and coefficient of thermal expansion of syntactic foams. The dynamic mechanical analysis results show that the storage modulus of syntactic foams increases with increasing glass hollow microsphere wall thickness and with decreasing glass hollow microsphere volume fraction in the glassy region at 40℃. The β-relaxation of the matrix resin found at 66.1 ± 2.0℃ was suppressed in the majority of syntactic foams, further improving the stability around typical application temperatures.

Strain rate sensitivity of polycarbonate and vinyl ester from dynamic mechanical analysis experiments

Measuring the strain rate sensitivity of materials is desired to improve the design of polymeric parts in automotive and aerospace structures. In this work, we present a technique for determining the mechanical response of polymers at different temperatures and strain rates by converting frequency-domain dynamic mechanical analysis (DMA) data to the time domain. Two polymers of practical interest, vinyl ester and polycarbonate, are examined. The modulus of elasticity in the linear region is measured as a function of the applied strain rate and compared to predictions from the DMA transformation technique. Close agreement between the results obtained from the two techniques is observed over the studied range of strain rates. The transformation technique only relies on the assumptions of the linear theory of viscoelasticity and is expected to be applicable to a wide range of polymers and can also be extended to polymer-matrix composites.

Mechanical Properties of Epoxy Matrix-Borosilicate Glass Hollow-Particle Syntactic Foams

Syntactic foams are particulate composites, which consist of a dispersion of hollow particles in a matrix. These materials are extensively used in the structures of underwater vehicles, but existing studies have shown that the commonly used soda-lime–borosilicate glass hollow particles are susceptible to significant degradation upon exposure to moisture. In this work, epoxy matrix syntactic foams are fabricated using borosilicate glass hollow particles that are not susceptible to degradation in wet environments. Nine compositions are fabricated and tested for quasi-static compressive properties, high-strain-rate compressive properties, and flexural properties. The quasi-static compressive strength and energy absorption are found to increase with composite density and the compressive strength is found to exceed that of similar syntactic foams using soda-lime–borosilicate hollow particles. The syntactic foams were observed to have 70 %–108 % higher peak stress in the high-strain-rate regime compared to the quasi-static values but the strength within the high-strain-rate regime was not dependent on the strain rate. The flexural properties were shown to have strong sensitivity to volume fraction of hollow particles.

Environmental Degradation of Carbon Nanofiber Reinforced Syntactic Foams

Hollow particle filled composites known as syntactic foams presently find applications in many high temperature, high moisture environments such as undersea drilling and oil exploration because of their low density and resistance to moisture uptake. Carbon nanofibers (CNFs) hold the promise of improving the strength of such composites. Syntactic foams with 1–5 wt.% carbon nanofiber-reinforced epoxy matrix and containing 15–50 vol.% glass hollow microballoons are characterized for environmental degradation using accelerated weathering in a 90°C water bath for two weeks and for residual flexural strength and modulus. The maximum weight gain observed after moisture exposure was 3.5% for the CNF/epoxy and 10% for the CNF/syntactic foam. Strength generally decreased after weathering by up to 69%, with the exception of the composites containing 5 wt.% CNF, which showed an increase in strength. This was attributed to swelling of the matrix leading to improved traction on the fibers.

Development of Lightweight Carbon Nanofiber Reinforced Syntactic Foam Composites

Syntactic foams are a class of hollow particle filled composites which have found many applications in the marine sector due to their outstanding specific compressive properties and tailorable buoyancy. A limitation of these composites is that the tensile and flexural properties are severely limited due to the addition of hollow particles. Carbon nanofibers reinforcement of the matrix has been explored as a means of improving the tensile properties of such composites without sacrificing light weight. The nanofibers are dispersed between the hollow particles and do not affect the packing efficiency of the filler. The unique electrical and thermal properties of CNFs also present opportunities to tailor these properties of the composite beyond the range traditionally achievable by only particles. Thermal and electrical properties of CNF syntactic foams will be examined with a focus on the potential applications of these composites.