The in situ shear response of the matrix in polymer matrix composites (PMC) has been studied. Torsion tests were performed on solid cylinders of unidirectional glass fiber reinforced/vinylester and unidirectional carbon fiber reinforced/vinylester composites. The composite specimens were subjected to a uniform rate of twist. From the composite stress-strain curve, a plot of tangent shear modulus vs shear strain was derived. Then, using the Halpin-Tsai equations, the in situ matrix shear modulus was determined. The in situ matrix properties obtained from glass/vinylester and carbon/vinylester composites were found to be different. In addition, the properties of the in situ matrix were found to be a function of fiber volume fraction and the elastic properties of the reinforcing fiber. The behavior of the in situ matrix as a function of the fiber volume fraction was explained by using a three cylinder interphase model. The validity of the interphase model in predicting the composite shear modulus was studied by comparison of results against a conventional 2 cylinder model.

1.
Agarwal, B. D., and Broutman, L. J., 1983, Analysis and Performance of Fiber Composites, 2 edition, Wiley, New York.
2.
Kyriakides
,
S.
,
Arseculeratne
,
R.
,
Perry
,
E. J.
, and
Liechti
,
K. M.
,
1995
, “
On the Compressive Failure of Fiber Reinforced Composites,” Proceedings of the Sixtieth Birthday Celebration of Prof. W. G. Knauss
,
Int. J. Solids Struct.
,
32
, pp.
689
738
.
3.
Piggot, M. R., Sandai, A., Chua, P. S., and Anderson, D., 1986, Mechanical Interactions in the Interphasial Region of Fibre Reinforced Thermosets, Composite Interfaces, North-Holland, Amsterdam.
4.
Pompe
,
G.
, and
Mader
,
E.
,
2000
, “
Experimental Detection of a Transcrystalline Interphase in Glass-Fibre/Polypropelene Composite
,”
Compos. Sci. Technol.
60
, pp.
2159
2167
.
5.
Waas
,
A. M.
,
1992
, “
Effect of Interphase on the Compressive Strength of Unidirectional Composites
,”
ASME J. Appl. Mech.
,
59
, pp.
183
188
.
6.
Williams
,
J. L.
,
Donellan
,
M. E.
,
James
,
M. R.
, and
Morris
,
W. L.
,
1990
, “
Elastic Modulus of the Interphase in Organic Matrix Composites
,”
Mat. Res. Soc. Symp. Proc.
, Vol.
170
, pp.
285
289
.
7.
Drzal
,
L. T.
,
Rich
,
M. J.
, and
Llyod
,
P. M.
,
1982
, “
Adhesion of Graphite Fibers to Epoxy Matrices: I. The Role of Fiber Surface Treatment
,”
J. Adhes.
,
16
, pp.
1
30
.
8.
Drzal
,
L. T.
,
Rich
,
M. J.
,
Koenig
,
M. F.
, and
Llyod
,
P. M.
,
1982
, “
Adhesion of Graphite Fibers to Epoxy Matrices: II. The Effect of Fiber Finish
,”
J. Adhes.
,
16
, pp.
133
152
.
9.
Hyer, M. W., and Waas, A. M., 2000, “Micromechanics of Linear Elastic Continuous Fiber Composites.” T. W. Chou, ed., Comprehensive Composite Materials, Vol. 1, Chapter 12. Elsevier Science.
10.
Lee
,
S. H.
, and
Waas
,
A. M.
,
1999
, “
Compressive Response of Fiber Reinforced Unidirectional Composites
,”
Int. J. Fract.
,
100
, pp.
275
306
.
11.
Nadai, A., 1950, Theory of Flow and Fracture of Solids, Vol. 1, Mc-Graw Hill, New York.
12.
Lyon
,
R. E.
,
1991
, “
Shear Strength of a Ductile Material from Torsion Test of Solid Cylinders
,”
J. Test. Eval.
,
19
, No.
3
, pp.
240
243
.
13.
Daniel, I. M., and Isahi, O., 1994, Engineering Mechanics of Composite Materials. Oxford Univ. Press.
14.
Jelf
,
P. M.
, and
Fleck
,
N. A.
,
1994
, “
The Failure of Composite Tubes Due to Combined Compression and Torsion
,”
J. Mater. Sci.
,
29
, pp.
3080
3084
.
15.
Hashin
,
Z.
,
1966
, “
Viscoelastic Fiber Reinforced Materials
,”
AIAA J.
,
4, pp.
1411
1417
.
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