Modified foam cores for full thermoplastic composite sandwich structures

Abstract

Full thermoplastic composite sandwich structures with a foam core offer the possibility to be manufactured by fusion bonding in significant shorter cycle times than thermoset-based sandwiches. However, the application of foam cores results in lower mechanical properties such as compression and shear strength compared to honeycomb cores, therefore foam-based sandwiches cannot compete with sandwich structures based on Aramid/phenolic honeycomb cores, the current state of the art. In order to improve the mechanical performance of foam core-based sandwiches while maintaining their advantages, concepts to reinforce the foams were developed in this study. By introducing rods either orthogonally or diagonally to the skin plane, which are fusion bonded to the skins during processing, the compression and shear properties can be improved by up to 1000% and 72%, respectively. Even when correcting for the weight increase, an improved specific compression strength could be achieved. And therefore, the pinning looks especially promising when only applied locally in highly loaded areas for example.

A review of mode I dominant interfacial fracture toughness test methods of skin-core bonding for thermoplastic composite sandwich structures

“…( 5) Debonding growth must be stable, although stick-slip growth may be permitted (6) Specimen response must be linear elastic and must be appropriate for analysis using linear elastic fracture mechanics (LEFM). (7) The test must result in the measurement of quasi-static values of Gc, including an initiation value and subsequent propagation values. (8) It must be possible to test a practical range of sandwich systems including structures with compliant composite facesheets.…”

“…For this reason, a number of different thermoplastic-based sandwich composite structures and processing techniques have been developed in recent years. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Sandwich structures in principle consist of a three-layer cross-section with a core and two covering facesheets. 25 The resulting composition is similar to an I-beam structure with a clear division of tasks between facesheets and core, following the stress distribution in the cross-section induced by bending loads.…”

Curved woven lattice truss sandwich panels strengthened by foams: Designing, manufacturing, and testing

“…22 The lightweight foam-filled can effectively improve the shear resistance of the structure, [23][24][25][26] through effectively restraining the bending deformation of the core piles. 27,28 Curved structures exhibit excellent performance with high strength, high ductility, explosion, and impact resistance. 29 Yang et al 30 discussed the effects of relative density, impact energy and impact position on impact behavior on carbon fiber composites and circular corrugated sandwich cylindrical plates, found that the maximum load and energy absorption changed with relative density, the impact response was related to the density of the impact position, but was not sensitive to impact energy.…”

“…The foam‐filled directly improves the compression resistance and provides lateral support for the core pillar and suppresses lateral movement when lateral buckling occurs 22 . The lightweight foam‐filled can effectively improve the shear resistance of the structure, 23–26 through effectively restraining the bending deformation of the core piles 27,28 . Curved structures exhibit excellent performance with high strength, high ductility, explosion, and impact resistance 29 .…”

Flexible polyurethane foam‐based sandwich composites: Preparation and evaluation of thermal, acoustic, and electromagnetic properties

“…The concept of sandwich composite was introduced in the early 20th century to the aircraft, automobile, and marine industries. The traditional sandwich composites commonly used in these fields were composed of metals and fiber‐reinforced plastic (FRP) to obtain very high strength and stiffness . Nowadays, sandwich composites, especially those with a low‐density core and excellent insulation characteristics become efficient structural systems that are suitable for a variety of civil applications, including floor and roof panels, pedestrian bridge decks, and cladding walls of buildings …”