Edgewise Compressive Strength Research Articles

Moisture absorption and mechanical degradation studies of polyurethane foam cored E-glass-reinforced vinyl-ester sandwich composites

The present paper explores the experimental observations and result of hygrothermic aging of polyurethane foam cored E-glass reinforced vinyl-ester sandwich composites for a long duration of time under salt fog exposure. Four types of sandwich specimens were used for the study. Polyurethane foam cored E-glass mat (woven roving, chopped strand mat, chopped strand stitched mat and stitch bond mat) type reinforcement in vinyl-ester sandwich composites were prepared by manual hand layup method using compression technique. The prepared specimens were tested for moisture up-take behavior and the resulting property degradation in terms of flexural strength, flatwise and edgewise compression strength. The mechanical properties under the salt fog exposure with 95% RH using artificial sea water fogging were monitored for 180 days. The specimens showed reduced strength in terms of core shear and facing bending strength, edgewise and flatwise compressive strength. Scanning electron micrograph of the fracture specimens show face sheet/core debonding.

Compressive Performance Investigation between Thin Honeycomb Paperboard and Corrugated Paperboard of Flute A

Thin honeycomb paperboard(THPB) is an emerging carton material instead of corrugated paperboard(CPB) recently, public research results and comparative data have not yet found at present. CPB of flute A is selected as contrast material in the paper since its thickness and density are similar to THPB, then properties of two kinds of paperboard are researched and compared according to test methods of edgewise compressive strength for sandwich structure, flatwise crush strength and edgewise crush strength for corrugated paperboard. The results showed that the compressive capacity of THPB in edgewise compressive, flatwise crush and edgewise crush performance is higher than that of CPB of flute A. THPB can be applied to carton for large and heavy product, especially for the package under multidirectional compression.

Relationship between the edgewise compression strength of corrugated board and the compression strength of liner and fluting medium papers

The compression strength of a corrugated board box is a direct measure of its stacking strength. The edgewise compression strength of corrugated board is the major contributor to the box stacking strength. This relation can be further extended to the critical strength properties of paper substrates. It was, therefore, the aim of this study to establish predictive mathematical correlations between corrugated board and paper compression properties after exposure to certain climate conditions. This would allow packaging technologists in the field to select adequate paper substrates, with certain strength characteristics, to manufacture corrugated board with the necessary compression strength for achieving a desired carton performance for certain climate conditions. The results of this study were used to determine the linear regression constants in the Maltenfort model by correlating the measured board edgewise compression strength (ECT) with the predicted strength, using the paper components' compression strengths, measured with the short-span compression test (SCT) and the ring crush test (RCT) methods. The obtained predictive mathematical models were as follows: ECT = 0.6982 (SCTL1 + SCTL2 + SCTL3 + α1SCTF1 + α2SCTF2) and ECT = 1.028 (RCTL1 + RCTL2 + RCTL3 + α2RCTF1 + α2RCTF2). The obtained models showed very high coefficients of determination (R 2 SCT = 0.9758, R2 RCT = 0.9625), which confirmed that they can be used successfully to predict the compression strength of corrugated board, using the measured paper compression strength (SCT or RCT) after exposure to constant climatic conditions. The results also indicated that the obtained plant-specific predictive mathematical models compared well to the overall linear models and that no major difference existed between the plants' capabilities to convert the paper compression strength into corrugated board edgewise crush strength. This suggested that a single set of predictive mathematical models can be utilised with a good degree of confidence in the South African corrugating industry.

Foam sandwich composites with cyanate ester based syntactic foam as core and carbon‐cyanate ester as skin: Processing and properties

AbstractFoam sandwich composites were processed using cyanate ester‐based syntactic foam as core and carbon fabric‐cyanate ester composite as skin. They were processed by a one‐step compression‐molding technique. The mechanical performance of the sandwich composites was evaluated in terms of flatwise tensile strength (FTS), flatwise compressive strength, and edgewise compressive strength. The dependency of these properties on the core composition was investigated. FTS initially increased with the increase in resin content of the syntactic foam core. However, higher resin content in the core led to a diminution in FTS due to high void content. The flatwise compressive strength and edgewise compressive strength and the corresponding moduli values showed an increasing trend with increase in resin content of the core despite the presence of voids at high resin content. The failure modes of the composites under different loading conditions have been examined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

An Experimental Investigation on Composites Through-The-Thickness Stitched Foam Core Sandwich Panels

This study explored the feasibility and potential benefits provided by the addition of through-the-thickness reinforcement to foam core sandwich structures. Through-the-thickness stitching is proposed to increase the interlaminar strength and damage tolerance of composite sandwich structures. A low-cost, out-of-autoclave processing method was developed to produce composite sandwich panels with carbon fiber face sheets, a closed-cell foam core, and through-the-thickness Kevlar stitching. The sandwich panels were stitched in a dry preform state, vacuum bagged, and infiltrated using Vacuum Assisted Resin Transfer Molding (VARTM) processing. For comparison purposes, unstitched sandwich panels were produced using the same materials and manufacturing methodology. Five types of mechanical tests were performed: flexural testing, flatwise tensile and compression testing, core shear testing, and edgewise compression testing. Drop-weight impact testing followed by specimen sectioning was performed to characterize the damage resistance of stitched sandwich panels. Compression after impact (CAI) testing was performed to evaluate the damage tolerance of the sandwich panels. Results show significant increases in the flexural stiffness and strength, out-of-plane tensile strength, core shear strength, edgewise compression strength, and compression-after-impact strength of stitched sandwich structures.

Repair Effectiveness Studies on Impact Damaged Sandwich Composite Constructions

Experimental studies were carried out using sandwich composite panel specimens, consisting of both polyurethane foam core (PUF) and aramid honeycomb core (Nomex) type constructions. These specimens were subjected to impact damage at energy levels ranging between 7.56 and 15.6 J. A ply-drop-patching technique was employed to repair the impact damaged sandwich specimens. The undamaged (virgin), impact damaged, and repaired specimens were then subjected to flexural (four point bending) and edgewise compression tests and strength recoveries were measured to determine the efficacy of the repair technique employed. In flexure, strength recoveries of up to 97% in PUF core and 90% in honeycomb core sandwich specimens were realized after repair, whereas in compression, the corresponding values were up to 90% in PUF core and 88% in honeycomb core sandwich specimens. A repair effectiveness factor (Ref) has been conceived and introduced to quantify the efficiency of the repair technique. Further, the repair quality was assessed using a simple NDT method prior to subjecting the sandwich specimens for destructive tests.

Effect of Microballoon Radius Ratio on Syntactic Foam Core Sandwich Composites

Hollow particles, called microballoons, are commonly used in the fabrication of syntactic foams, which are used as core materials in sandwich composites. The present experimental investigation aims at characterizing five different types of syntactic foam core sandwich composites for their edgewise compressive strength. The microballoon volume fraction is maintained at 0.65 in each type of syntactic foams. The five types of microballoons used in the study have the same mean outer diameter of about 40 mm but different wall thickness causing a difference in their densities and strengths. The differences in the compressive strength and modulus of sandwich composites are related to the microballoon radius ratio, which is defined as the ratio of the internal to the external radii of the microballoons. It is observed that the compressive strength and modulus of syntactic foams increase with a decrease in the microballoon radius ratio. The specimen fracture features are also discussed.

유한요소법에 의한 Corrugated Board의 휨 발란스 해석

The top-to-bottom compression strength of corrugated board box is the most important mode of loading during it's no, and it depends largely on the edgewise compression strength of the corrugated board in the cross-machine direction and to a considerable extent on the flexural stiffness in both principal directions (CD; cross-machine direction, MD; machine direction) of the corrugated board. Corrugated board is a sandwich structure with an orthotropic property. The purpose of this study was to elucidate the principal design parameters for board combination of corrugated board from the viewpoint of bending strength through the finite element analysis [FEA] fur the various corrugated board. In general, the flexural stiffness [FS] in the MD was 2-3 times larger than that in the CD, and the effect of liner for the FS of corrugated board was much bigger than that of corrugating medium. The flexural stiffness index [FSI] was high when the stiffness of liner was in the order of inner, outer, and middle liner in double-wall corrugated board [DW], and the effect of the stiffness arrangement or itself reinforcement of corrugating medium on the FSI was not high. In single-wall corrugated board [SW] with DW. the variation of FSI with itself stiffness reinforcement of liner was much bigger than that with stiffness arrangement of liner. The highest FSI was at the ratio of about 2:1:2 for basis weight distribution of outer, middle, and inner liner if the stiffness of liner and total basis weight of corrugated board were equal in DW Secondarily. basis weight was in the order of inner, outer, and middle liner. However, the variation of FSI with basis weight distribution between liner and corrugating medium was much bigger than that with itself basis weight distribution ratio of liner and corrugating medium respectively in both DW and SW. md the FSI was high as more total basis weight was divided into liner. These phenomena fur board combination of corrugated board based on the FEA were well verified by experimental investigation.

Skin Wrinkling of Impact Damaged Sandwich Composite

The effect of impact damage on the edgewise compressive properties and failure mechanism of a sandwich polymer composite is investigated. The composite was made from a thick core of polyvinyl chloride foam sandwiched between thin face skins of glass fibre reinforced polymer laminate. This material was impacted at a low energy that caused damage to the skin and at a high energy that severely damaged the skin and core. The unimpacted sandwich composite failed in edgewise compression by crimping of the foam core. When damage created by the low and high energy impacts exceeded a critical size the failure mechanism changed suddenly to wrinkling of the impacted skin. Failure by skin wrinkling resulted in large reductions to the edgewise compressive stiffness and strength of the sandwich composite. A model is proposed to determine the edgewise compressive stress required to induce skin wrinkling in impact damaged sandwich composites. Good agreement was found between the theoretical and measured skin wrinkling stresses in some cases.

More Rapid Edgewise Crush Test Methods

Abstract The use of paraffin wax to reinforce the loading edges of corrugated fiberboard edge-crush specimens requires that the specimens be reconditioned after waxing. The traditional practice employing a 24-h reconditioning period is a conservative approach based on the moisture response rate of corrugated containers. An interlaboratory study was conducted to determine the effect of reconditioning time on edgewise compressive strength of waxed specimen prepared by standard test methods. Results showed that reconditioning time can be reduced from 24 h to 2 h wish no significant change in test values. The results apply to flexible-beam and rigidplaten loading machines, but at conventional loading speeds, the flexible-beam machine yielded higher overall streagth values. Other tests were conducted to evaluate the performance of an edge-clamping fixture for use with unwaxed specimens. When tested with heavy basis weight materials, the fixture did not yield equivalent results compared to those obtained with lighter grade waxed apecimens.

A mathematical model of compressive strength in paperboard

Experimental evidence for a correlation between paperboard edgewise compressive strength and the product of the in-plane normal stiffness and out-of-plane shear stiffness is presented. A mathematical theory, which describes compressive failure as interlaminae shear failure due to prebuckling bending of an initially curved ‘critical’ lamina, is developed. The theory is in accord with failure analysis observations and with the empirical relationship.