| 1. |
- Adolfsson, Erik, et al.
(författare)
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Matrix crack induced stiffness reductions in [(0(m)/90(n)/+theta(p)/-theta(q))(s)](m) composite laminates
- 1995
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Ingår i: Composites Engineering. - : Elsevier BV. - 0961-9526. ; 5:1, s. 107-123
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Tidskriftsartikel (refereegranskat)abstract
- Two- and three-dimensional linearly elastic glass/epoxy and carbon/epoxy laminates of the type [(0m/90n/ + theta(p)/ - theta(q))s]M containing periodically distributed matrix cracks have been analysed by aid of the finite element method. The presented finite element model enables modelling of several important thick and thin ply stacking sequences like cross-plies, angle plies and quasi-isotropic laminates. Due to periodicity it suffices to model a representative volume element of the laminate. The boundaries of this unit cell represent prospective crack surfaces. In this way varying crack configurations and crack densities could be simulated. By application of periodic boundary conditions the stiffness tensors for laminates containing different crack configurations were calculated. The results are presented in the form of reduced engineering stiffness parameters as functions of matrix crack densities for a thick quasi-isotropic [(0-degree/90-degrees/ + 45-degrees/ -45-degrees)s]M glass/epoxy laminate, a thick [(0-degree/90-degrees + 55-degrees/ - 55-degrees)s]M carbon/epoxy laminate and a thin (0-degree/ +45-degrees/ -45-degrees)s glass/epoxy laminate. Comparisons are made to an approximate analytic model developed previously. An excellent agreement between the analytic predictions and the finite element results was found for all cases under consideration.
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| 2. |
- Holmbom, Anders, et al.
(författare)
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A homogenization procedure for computing effective moduli and microstresses in elastic composite materials
- 1992
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Ingår i: Composites Engineering. - 0961-9526. ; 2:4, s. 249-259
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Tidskriftsartikel (refereegranskat)abstract
- Effective properties and microstress variations of elastic fiber composites are studied by means of the homogenization method. Some numerical results are obtained by using the finite element code HOMO. The model problem is a two-phase elastic fiber composite consisting of boron fibers in an epoxy matrix with various fractions of the two phases. The homogenized stiffness matrices are compared with the weighted harmonic and arithmetic means, respectively.
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| 3. |
- Lukkassen, Dag, et al.
(författare)
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Some engineering and mathematical aspects on the homogenization method
- 1995
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Ingår i: Composites Engineering. - 0961-9526. ; 5:5, s. 519-531
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Tidskriftsartikel (refereegranskat)abstract
- Effective properties and local stress variations of elastic fiber composites are studied by means of the homogenization method. Two different methods, “the displacement method” and “the force method”, for solving the so called cell problem are derived, applied and compared. Numerical results for three different types of representative volume elements are presented. We also calculate the effective moduli of a unidirectional fiber composite for different volume fractions of fibers. The numerical results are discussed and compared with the Hashin-Shtrikman bounds.
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| 4. |
- Östlund, Sören, et al.
(författare)
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Numerical-Analysis Of Matrix-Crack-Induced Delaminations In [+/-55-Degrees] Gfrp Laminates.
- 1992
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Ingår i: COMPOSITES ENGINEERING 2. - 0961-9526. ; 2:3, s. 161-175
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Tidskriftsartikel (refereegranskat)abstract
- In this paper a three-dimensional glass epoxy angle-ply laminate of the type [+/- 55-degrees] containing matrix cracks and two types of matrix-crack-induced interlaminar local delaminations has been numerically analyzed by the finite element method. Due to periodicity and symmetry only a representative volume element in the form of a parallelepiped bounded by neighbouring matrix cracks needs to be modelled. The additional contributions to the reduction of stiffness coefficients due to local delaminations are compared to the stiffness of undamaged laminates and laminates containing only matrix cracks. Furthermore, the growth of delaminations and progressive matrix cracking are investigated by calculations of their respective total energy release rates as functions of the delamination size and matrix crack density. Implications of the influence of matrix-crack-induced delaminations on the mechanical behaviour of the composite laminate are discussed.
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