Abstract
This paper focuses on the dynamic tensile response of glass-graphite/epoxy composites illustrating improvement in energy absorption through hybridization. The dynamic response and energy absorption characteristics of pultruded hybrid combinations of glass and graphite fibers in an epoxy matrix subjected to induced transverse tension at high strain-rate in a modified Split Hopkinson Pressure Bar (SHPB) apparatus, are presented. Transverse tensile strength was determined by diametral compression of disc samples (Brazilian indirect tensile test method). Diametral crack initiation and strain to failure were monitored with a Shimadzu HPV-2 high-speed video camera at a recording speed of 500,000 fps and Digital Image Correlation (DIC). Adequate measures were taken to ensure that initiation of specimen failure occurred at the exact center of the disc specimen, and propagated through the diameter along the compressive loading axis, for the induced transverse tension tests to be valid. A study of the strength and specific energy absorption demonstrates the benefits of hybridization. Under induced transverse tensile loading condition, the pure glass/epoxy (GL60) exhibited higher strength than pure graphite/epoxy (GR60). Pure graphite/epoxy (GR60) has higher specific energy absorption capacity than pure glass/epoxy (GL60) in transverse tension. Among all hybrids, GR30 has the highest specific energy absorption under transverse tension. Overall, hybrid GL48, with 48% low-cost glass fibers in the inner core and 12% high-cost graphite fibers in outer shell, was found to exhibit better performance under induced transverse tension at high strain-rates, showing the benefits of hybridization.
Highlights
Fiber-reinforced pultruded composites with improved structural strength, mechanical properties and lower weight are replacing traditional materials such as steel, wood, aluminum, in several structural applications [1]
Brazilian tests were conducted at high strain-rate to induce transverse tension in the pure glass, pure graphite, and hybrids of glass-graphite fiber/epoxy disc specimens
Brazilian indirect tensile tests were performed on pultruded hybrid composite specimens made of glass and graphite/epoxy using a modified Split Hopkinson Pressure Bar (SHPB)
Summary
Fiber-reinforced pultruded composites with improved structural strength, mechanical properties and lower weight are replacing traditional materials such as steel, wood, aluminum, in several structural applications [1]. Mantena [2]-[9] performed several quasi-static and dynamic investigations on pultruded glass and graphite/epoxy “hybrids”. Whereas pure glass/epoxy exhibited higher shear modulus than pure graphite/epoxy, the hybridization of these two materials with specific amount of glass fibers in the outer shell region resulted in better dynamic performance. Low-velocity impact response characteristics and the influence of hybridization on the crashworthiness and energy-absorption of pultruded glass-graphite/epoxy composite beams were investigated using a drop-weight impact test system [8] [9]. Hybrids with graphite fibers located in the outer region showed higher flexural stiffness, propagation energy, ductility, and failure index. They had lower initiation energy and a tendency to delaminate [9]
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