High Strain Rate Effects for Composite Materials

Abstract

We have been developing the capability to characterize the high strain rate response of continuous fiber polymer composites. The data presented cover strain rates from 0/s to 3000/s. A combination of test machines and specimen geometries was investigated. Strain rates from 0 to 100/s were generated using conventional and high-speed hydraulic test machines. Strain rates from 10 to 1000/s were generated using a high-energy drop tower, and rates from 1000 to 3000/s were generated using a split Hopkinson bar. Strain rates above 100/s have only been generated for uniaxial compression. Our efforts have primarily focused on developing the high-energy drop tower for these purposes. Specimen geometries for compression include tapered cubes, one-inch tubes, and solid rods. For tension, a smaller 1.27-cm-diameter version of our 5.08-cm-diameter multiaxial test specimen was developed and has been successfully used at strain rates up to 100 per second. Fixtures were also developed for performing high strain rate shear testing and through thickness penetration studies of composite plates. The objective of these experiments is to develop dynamic material models for use in finite element design tools. This presentation will focus on the methods and results obtained from this study.

The static and high strain rate behaviour of a commingled E-glass/polypropylene woven fabric composite

“…The average compression strength increased by a significant 87% between quasi-static and 126 s À1 strain rates. The increase in compression modulus and strength may be attributed to the viscoelastic effects in the matrix materials and the time dependent nature of damage accumulation [29,34]. The Y-C strain rate equations fit the experimental results well for the dynamic compressive modulus and strength over the entire strain rate range in this study (see Fig.…”

“…The increase in tensile modulus and strength is generally explained by a combination of several factors including the viscoelastic nature of the polymeric matrix [29], i.e. stiffening with increased rate of loading, and following Welsh and Harding [30], the woven structure and geometry of the composite.…”

“…18b shows fibre micro-buckling which leads to fibre kinking followed by failure of the fibres and matrix through the thickness of the specimen along a distinct shear band fracture plane. The micro-buckling in the fibres may be attributed to local premature failure of the surrounding matrix [29]. A detailed view of through-thickness shear failure in the fibres and matrix is shown in Fig.…”

Strain rate effects on the mechanical properties of polymer composite materials

“…29 Strain rates from 0 to 100 s Ϫ1 were generated using conventional and high-speed hydraulic test machines, those from 10 to 1000 s Ϫ1 were generated using a high energy drop tower, and those from 1000 to 3000 s Ϫ1 were generated using a split Hopkinson bar. The experimental results indicated an increase in both the compression and the tensile properties (strength and modulus) with increasing strain rate.…”

Strength and Failure Modes of Hoop Wound CFRP Tubes Under Compressive High Rates of Loading

“…It revealed that the most common dynamic compression test method utilized is the split Hopkinson bar technique (SPHB) [6][7][8][9][10], which generates strain rates of the order of 1000/s. The second most common test technique, instrumented drop weight system, has been used by Montiel and Williams [11], Groves et al [12], Hsiao et al [13,14] and Lifshitz [15] to investigate compressive properties of composite. The drop weight system has certain advantages but the system is very sensitive to contact conditions between the impactor and specimen, and to spurious noise from ringing and vibrations.…”