Core Reinforcement Research Articles

Mold Filling Simulation of Sandwich Composite Structures Manufactured by Liquid Molding: A Parametric Study

The mold filling stage in the manufacturing of sandwich composite structures with fiber reinforced foam core was studied with numerical simulations. Three different geometries of sandwich core reinforcement were considered in the form of fiber layers forming angles of 450 or 900 with the facings or in the form of equally spaced separate strands (webs). The influence of variable core and face reinforcement permeability and location of the injecting edge on the flow front progression and filling time was explored. The results suggest that permeability of the core has a significant influence on filling pattern and mold filling time. Experimental and predicted flow front developments and flow rates for a radial injection case under constant pressure were compared.

Performance of Sandwich Structures with Composite Reinforced Core

Sandwich panels with a foam core reinforced with composite laminates were investigated. The effective material properties of the reinforced core were obtained by homogenization. The general equations of equilibrium for sandwich plates were derived and used for parametric studies of the behavior of the sandwich plates. Three Point Bending tests were performed to experimentally measure the bending stiffness along with the strength of sandwich beams. The test results were also used to verify the analytical solution obtained by using the sandwich plate theory. It was found that local indentation must be included in the theoretical model. Static punching tests (SPT) and low velocity impact (LVI) tests were performed to investigate the behavior of sandwich plates under static and dynamic point loads. The force-displacement relations were modeled based on indentation data. The damage modes, effects of the core reinforcement, and effects of the foam were investigated. A second manufacturing method for constructing the reinforced core was presented, and its properties were compared with those obtained using the original manufacturing method.

Performance of Sandwich Structures with Composite Reinforced Core

Sandwich panels with a foam core reinforced with composite laminates were investigated. The effective material properties of the reinforced core were obtained by homogenization. The general equations of equilibrium for sandwich plates were derived and used for parametric studies of the behavior of the sandwich plates. Three Point Bending tests were performed to experimentally measure the bending stiffness along with the strength of sandwich beams. The test results were also used to verify the analytical solution obtained by using the sandwich plate theory. It was found that local indentation must be included in the theoretical model. Static punching tests (SPT) and low velocity impact (LVI) tests were performed to investigate the behavior of sandwich plates under static and dynamic point loads. The force-displacement relations were modeled based on indentation data. The damage modes, effects of the core reinforcement, and effects of the foam were investigated. A second manufacturing method for constructing the reinforced core was presented, and its properties were compared with those obtained using the original manufacturing method.

Mechanical properties of fiber reinforced lightweight concrete composites

Hybrid composites with variable strength/toughness properties can be manufactured using combinations of brittle or ductile mesh in addition to brittle and ductile matrix reinforcements. The bending and tensile properties of thin sheet fiber cement composites made from these mixtures were investigated. Composites consisted of a woven mesh of either polyvinyl chloride (PVC) coated E-glass or polypropylene (PP) fibers for the surface reinforcement. In addition, chopped polypropylene, acrylic, nylon, and alkali-resistant (AR) glass fibers were used for the core reinforcement. It is shown that by controlling fiber contents, types, and combinations, design objectives such as strength, stiffness and toughness, can be achieved. Superior post-cracking behavior was measured for composites reinforced both with glass mesh and PP mesh. Load carrying capacity of PP mesh composites can be increased with the use of 1% or higher chopped PP fibers. Glass mesh composites with short AR glass fibers as matrix reinforcement indicate an increased matrix cracking strength and modulus of rupture. Combinations of PP mesh/short AR glass did not show a substantial improvement in the matrix ultimate strength. An increased nylon fiber surface area resulted in improved post peak response.

A comparative study of LECA concrete sandwich beams with and without core reinforcement

Lightweight concrete beams of sandwich construction with and without core reinforcement were made using Lightweight Expanded Clay Aggregate (LECA) concrete cores, and tested in four-point loading. The programme included tests on ordinary dense concrete beams which had the same reinforcement, and were used as controls. Results of beam deflections, strains and ultimate loads were recorded. The comparative study illustrated that sandwich beams cored by LECA concrete, with the cores reinforced, had sufficiently good shear resistance for the beams to fail by yielding of the tension steel, and that if strength-to-weight ratio is taken as a measure of efficiency, the sandwich beams were more efficient structures than the ordinary dense beams.