PSI - Issue 63

Kamila Kotrasova et al. / Procedia Structural Integrity 63 (2024) 27–34

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high specific strength and stiffness compared to other materials, particularly metals and alloys by Agarwal et al. (1987) or Altenbach et al. (2001) or Barbero (2007) or Bareš (1988) or Bathe (1996) or Bernadou et al. (1972) or Zienkiewicz (1971). The use of composite laminates reinforced with synthetic fibers is widely adopted for structural applications because they allow for weight reduction while maintaining high specific mechanical properties by Frosting et al. (2003) or Gürdal et al. (1999) or Kormanikova et al. (2022) or Al Ali at al. (2023) or Kissing (2000) or Liu et al. (1993) or Miki (1993) or Moita et al. (2000). However, these materials are relatively expensive, and their main disadvantage is their susceptibility to damage under impact loading due to their brittle behavior by Palani et al. (1992) or Kormanikova et al. (1992) or Seremekun et al. (2001). The use of the laminated composites in many engineering applications has expanded rapidly over the past four decades Stegman et al. (2002) or Matthews et al. (2004) or Reddy (2000) or Kassapoglou (2013) or Chapelle et al. (2011) or Kormanikova et al. (2022) or Khayal et al. (2022). In particular, laminated composite plates are often used in various engineering applications and have widespread use in various fields of science, including aerospace, marine, mechanical, and modern highways by Vertonghen et al. (2011) or Müzel et al. (2020). The use of composite plates in construction, bridges, can lead to economic solutions and allows the construction of aesthetic, and safe structures. The required knowledge, which is necessary to know how to manage composite materials, composite structural elements, requires FEM numerical simulations by Koruche et al. (2015) or Ozankaya et al. (2023). In this paper, the study of the effect of layer orientation on the behavior of the multilayered composite plates is study by taking three-layer laminate composite for different type of laminates with different symmetric and unsymmetric orientation of lamina:  symmetric orientation: 0/90/0, 90/0/90, 45/-45/45, -45/45/-45,  unsymmetric orientation: 0/45/90, 0/-45/90, 90/45/0, 90/-45/0.

Nomenclature N

vector of normal forces vector of shear forces M vector of bending moments strain vector vector of curvatures A in-plane stiffness matrix coupling stiffness matrix D bending stiffness matrix � transerse shear stiffness matrix W* strain energy 2. Shear deformation theory for laminates V vector of transverse shear strains B

The classical laminate theory allows to calculate the stresses and strains with high precision for very thin laminates except in a little extended region near the free edges by Brunbauer et al. (2015). The validity of the classical theory has been established by comparing theoretical results with experimental tests and with more exact solutions based on the general equations of the linear anisotropic elasticity theory by Ciunta et al. (2023) or Sejnoha (2000). If the width to-thickness ratio is less about 20, the results derived from the classical theory show significant differences with the actual mechanical behaviour and the modelling must be improved Surendra et al. (2023). A first improvement is to include approximately the effect of shear deformation in the framework of a first-order displacement approach. A further improvement is possible by introducing correction factors for the transverse shear moduli. In the shear deformation theory, the actual deformation state is approximated by 5 independent two-dimensional functions u , v , w , and , in the classical theory by 3 functions u , v , w , respectively. The strains are deduced from the displacements. The components of the strains