Publications

Materials Testing and Technical Services Ltd (MTTS Ltd)

Publications by Company's Directors

Polymers and Polymer Composites, Vol. 20, No. 5, pp. 411-423, 2012

Paper: Compression and Recovery Behaviour of Polyamide-6 Based Foams

V.G. Izzard, H. Hadavinia, V.J. Morris, P.J.S. Foot, L.M. Wilson, K. Hewson

Abstract: This paper presents experimentally determined compression sets and compression behaviour of two closed cell, cross linked foam materials; ZOTEK N B50 (Nylon 6) and ZOTEK N A30 (Nylon 6/Polyolefin alloy). This work forms the basis for future investigations into post-impact type scenarios using these foams.Compression set performance was measured at 25.0, 37.5 and 50.0% strain at nine temperatures covering the range of -5 to 90^oC. Compression tests at constant strain rates were conducted at four temperatures covering the range 23 to 90^oC. Also the compression tests at 23^oC were repeated at four strain rates between 0.3 and 550 hr^-1 to determine strain rate dependency. The Nagy and William Landel Ferry relationship equations were applied to the experimental results and equations were derived which allow the performance of the two Polyamide based foams to be interpolated over the range of study.The basic properties of interest of the base polymers have been assessed and are presented and discussed in relation to the performance of the foam materials.

The Structural Engineer, Volume 83, No. 12 - 21^st June 2005
Paper: Unreinforced solid dense concrete block walls constructed using thin joint technology
A. N. Fried, E. Marrocchino, C. H. Bradsell, Prof J. J. Roberts

Abstract: The transverse lateral load capacity of masonry built using solid dense concrete blocks with thin joint mortar is up to 4.0 times that of similar blockwork constructed using conventional mortar. Both the mortar properties and the constituents of the parent material forming the block alter the joint strength resulting in enhancements to tensile flexural bond strength. Testing on two block types and one mortar has been undertaken and verifies the trend. Essentially when thin joint technology is employed, in conjunction with solid dense concrete blocks, the masonry behaves more as a concrete plate than conventional blockwork.

Key Engineering Materials, Vol 488-489, pp. 286-289. (2012)
Paper:Performance of Nylon Based Polymer foams at Elevated Temperature Under Tensile Loading

V.G. Izzard, C.H. Bradsell, H. Hadavinia, V.J. Morris, P.J.S. Foot, L.M. Wilson, K. Hewson

Abstract: One of the primary applications of polymer based cellular solids is to act as an energy absorbing material during impact where compressive strain rates may reach 500-800/s. In reality, impacts occur over a wide range of temperatures and velocities at different angles of incidence. Understanding and modelling the behaviour of the polymer foams requires characterisation of the material response in detail. The stress-strain response that covers both compressive and tensile behaviour for a wide range of strain rates and temperatures are needed to characterize the mechanical performance of polymer foams as polymeric foams are highly nonlinear materials that undergo large deformation in crashworthiness related cases. It is reported in literature that any increase or decrease in temperature over the glass transition region can cause changes by order of magnitude in elastic modulus of polymeric foams. However, creation of cross linking at high temperature can affect the elastic modulus. In this work, the behaviour of two, polyamide-6 (PA-6) based closed cell foams at elevated temperatures were investigated covering the glass transition temperature. This work presents the variation of elastic and tangent modulus of two low densities PA-6 and PA-6/polyolefin (Nylon alloy) based foams. Empirical equations have been proposed to allow the prediction of modulus over a temperature range of 23^oC to 12^oC for these materials.

Key Engineering Materials, Vol 417-418, pp. 933-936. (2010)
Paper: Investigation of the Compression Recovery Properties of Polyamide-6 Cellular Solid over the Temperature Range of -5 ^oC to 90 ^oC

V.G. Izzard, C.H. Bradsell, H. Hadavinia, V. Morris, P. Foot, N. Witten

Abstract: It is a fundamental response of any polymeric foam material to undergo non-recoverable deformation following the application of a defined compressive strain, exacerbated by temperature and humidity. This process is commonly referred to as compression set. The ability to predict recovery after the application of a compressive strain is crucial to both the manufacturers and end users of foam materials. Specific compression set test procedures have been established to quantify the extent of non-recoverable deformation in specific foam types but to date no general predictive approach exists. In this work, compression set (fixed strain) tests were undertaken on a cellular polyamide-6 material at various temperatures (-5°C to 90°C) and the foam recovery monitored over time periods in excess of those dictated by standard methods (ISO 1856 [1]). An empirical formula has been proposed to allow the prediction of recovery after compressive strain, covering recovery periods from 10 minutes to 24 hours (up to 168 hours at 23°C).

Fourth International Conference on FRP Composites in Civil Engineering (CICE 2008); 22 - 24 July 2008, Zurich, Switzerland.
Paper: Application of FRP materials for retrofitting of RC beams after shear failure
T. Donchev, G. Thomopoulos, C.H. Bradsell

Abstract: Fibre reinforced polymers (FRP) are being increasingly used for strengthening of reinforced concrete structural elements. One of the primary areas for their application is strengthening and retrofitting for shear loading. Problems and defects caused by shear loading are quite common occurrence during earthquakes as well as in cases of application of significant point loads. The role and effect of those applications are still subject to investigation with the number of influencing factors being high and methods of application varying significantly. Overview of some previous investigations and an experimental study are conducted to investigate the problems connected with the application of CFRP laminates, CFRP and GFRP wraps for shear strengthening and retrofitting. The experiments are based on full scale reinforced concrete beam modelling with the strengthening applied to beams previous failed by shear loading. Comparison with similar test using conventional steel bar strengthening has been made. Experimental data and analysis prove the effectiveness of the FRP applications. Comparison of the results obtained via different methods of strengthening and with existing data has been conducted. Final conclusions and recommendations for future research are offered.

The Journal of Chemical Thermodynamics, Volume 28, Issue 6, June 1996, Pages 637-646
Paper: (p,ρ,T) of liquid n-octane obtained with a spherical pycnometer at temperatures of 298.03 K and 313.15 K and pressures in the range 0.7 MPa to 32 MPa
A.R.H. Goodwin, C.H. Bradsell, L.S. Toczylkin

Abstract: The density ρ of n-octane at temperatures of 298.03 K and 313.15 K and at pressures between 0.7 MPa and 32 MPa have been obtained with a pycnometer. The results which we estimate have a best-case precision of ± 7x10^-5 ρ, are compared with values reported in the literature where the differences are less than ± 4x10^-4 ρ. At each temperature and pressure the cell volume V_c was obtained from the mass of mercury required to fill it at T= 293.12 K and 0.813 MPa and from the literature values of the mechanical properties of Inconel 625 from which the cell was formed. The volume was also obtained with a mercury-filled positive displacement pump at three temperatures between 298.15 K and 333.15 K and pressure below 30 MPa. The volumes so determined differed by less than 6x10^-5 V_c from the calculated values.

The Journal of Chemical Thermodynamics, Volume 23, Issue 10, October 1991, Pages 951-956
Paper: Measurement of the densities of complex fluids: results at temperatures between 288 K and 343 K and at pressures up to 30 MPa for each of two mixtures (crude oils) of specified composition
A.R.H. Goodwin, C.H. Bradsell, L.S. Toczylkin

Abstract: The densities of two complex mixtures at temperatures between 288 K and 343 K and at pressures up to 30 MPa have been obtained using a direct technique. Both fluids are crude oils, and have bubble pressures greater than 0.6 MPa in our temperature range. Empirical representations are provided for the experimental results.

The Journal of Chemical Thermodynamics, Volume 23, Issue 9, September 1991, Pages 883-899
Paper: Measurement of the densities of complex fluids: apparatus, validation, and results for water and for each of three complex mixtures (retrograde condensates)
A.R.H. Goodwin, C.H. Bradsell, P.L. Bryant, L.S. Toczylkin

Abstract: An apparatus for determining liquid densities with a fractional precision of 0.0002 is described. The cell volume was obtained from the mass of mercury required to fill it at temperatures between 278 K and 389 K at pressures below 30 MPa. To test our equipment and experimental methodology, the density of water was measured over the temperature range 278 K to 353 K at pressures up to 30 MPa. Our results for water lie within 0.0004 g cm^-3 of the literature values, about twice our estimated precision. The densities of three complex mixtures have been measured at temperatures between 278 K and 313 K at pressures up to 30 MPa. All three are retrograde-condensate fluids: two contain significant quantities of dissolved gas and have bubble pressures greater than 2 MPa in our temperature range; the other has a bubble pressure of 0.1 MPa at 293 K.

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