Vol.2, No1&2, 2002, pp. 15-19
UDC 620.178.7:[678.686-1:661.666

THE EFFECT OF FIBER ORIENTATION ON IMPACT TOUGHNESS AND FRACTURE PROPERTIES OF CARBON FIBER-EPOXY COMPOSITE

Meri Burzić 1

Stojan Sedmak 2

Milorad Zrilić 2

Zijah Burzić 3

Dragan Jaković 3

Dejan Momčilović 3

1 Military Technical Institute, Belgrade

2 Faculty of Technology and Metallurgy, University of Belgrade

3 Institute for Material Testing, Belgrade

Abstract

The effect of carbon fibers orientation in a composite with epoxy matrix on the impact and fracture toughness is experimentally analyzed by testing of Charpy type V notched specimens and notched specimens of modified CT form (with sharp notch tip as replacement for fatigue pre-crack). Specimens were produced from samples with carbon fiber orientation [±45]16s, [0/90]16s, and also with combined composition [02/90-/±45/90/02]4s.

Specimens with V notch have been tested on instrumented Charpy machine, enabling to separate crack initiation and propagation energies. Stress intensity factor Kc had been selected as fracture parameter.

Total impact toughness values have shown that highest impact resistance belongs to [0/90]16s, as expected, but the values for [02/90/±45/90/02]4s are also satisfactory, with convenient ratio of crack propagation to crack initiation energies.

Modified CT specimen testing have shown close and satisfactory results for stress intensity factor of two samples ([0/90]16s and [02/90/±45/90/02]4s), and for third sample [±45]16s this value is about 20% lower.

Having in mind other benefits with [02/90/±45/90/0-2]4s, it can be recommended as superior in spite of somewhat lower impact energy.

Keywords: composite, carbon fibers, epoxy resin, fiber orientation, impact testing, stress intensity factor

full article - only in Serbian (768 kB)