Mechanical Properties of Optically Transparent, Multi-Layered Laminates


The objective of this investigation was to study how the mechanical properties of an optically transparent composite varied with the geometrical arrangement, stacking sequence, of polymethylmethacrylate (PMMA) (designated as P) and composite (designated as C) layers. The multi-layered composites (about 6.63 mm thick) were highly transparent between 22 to 46°C in the visible region. As expected, the sandwich structure, (CCPP)s had the highest Young's modulus while (PCCP)s and (PPCC)s composites had the highest flexural strength and work of fracture, respectively. The flexural strength of these laminated composites, which contained only 0.8 vol % fibre without any coupling agent, was up to 21% higher than that of pure PMMA. The stress distribution through the thickness at the midpoint of a sample loaded in three-point bending was computed by the finite element method (FEM). The computed stress distribution allowed the expected point of failure to be established. The relationship between the stacking sequence, stress level under a given load, and strength was also investigated. The observed fracture modes were complex and the maximum stress failure criterion did not fit these composites. The fracture was always complex (tensile and shear), starting with tensile failure followed by shear mode (delamination) and another tensile mode. The first crack always commenced at a PMMA layer adjoining the composite layer which contained the highest stress. The optimum stacking sequence when such composites are used as a window is concluded to be (PCCP)s, since this sequence had the highest flexural strength (141 MPa) and a moderate work of fracture (37 kJ m-2).


Materials Science and Engineering

Keywords and Phrases

Bending strength; Crack propagation; Delamination; Elastic moduli; Finite element method; Fracture testing; Loads (forces); Polymethyl methacrylates; Shear strength; Stress concentration; Tensile strength; Multilayered laminates; Polymethylmethacrylate (PMMA) composites; Stacking sequence; Laminated composites

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version


File Type





© 1996 Springer Netherlands, All rights reserved.

Publication Date

01 Dec 1996