HexWeb® CR-PAA

1 of 20 products in this brand
5052 and 5056 expanded aerospace grade aluminum honeycomb materials are available in a wide selection of cell sizes and foil gages. The HexWeb® CR-PAA coating has been developed to offer superior protection for aluminum honeycomb exposed to corrosive environments. The HexWeb® CR-PAA system offers a clear protective film that interacts with the aluminum surface forming a stable, tightly adherent bond.

Functions: Core Material

Core Type: Aluminum Honeycomb

Chemical Family: Aluminum Compounds

Technical Data Sheet

Knowde Enhanced TDS

Identification & Functionality

Chemical Family
Composite Materials Functions

Features & Benefits

Product Highlights
  • Superior corrosion protection over standard aluminum cores
  • Enchanced bond strength and durability
  • Improved bonded assembly part life

Applications & Uses

Applications

HexWeb® CR-PAA is designed for aircraft structures that are exposed to demanding environmental conditions. HexWeb® CR-PAA outperforms standard AMS-C-7438 core in salt spray and crack propagation tests.

Properties

Mechanical Properties

Table I: HexWeb® CR-PAA Honeycomb Mechanical Properties

Typical values (typ) are presented below, as well as minimum average (min) for a product type.

 

Cell Size

Nominal Density pcf

Compressive Strength

Crush Strength psi

Plate Shear
Bare Stabilized L Direction W Direction
Strength psi Strength psi Modulus ksi Strength psi Modulus ksi Strength psi Modulus ksi
typ typ min typ min typ typ typ min typ typ min typ
5052 1/8 4.5 550 375 570 405 150 260 340 285 70 220 168 31
1/8 6.1 980 650 1020 680 240 450 560 455 98 340 272 41
1/8 8.1 1500 1000 1560 1100 350 750 800 670 135 470 400 54
1/8 12 2700 2100 2900 2200 900 1940 1250 1430 1000
5/32 3.8 395 285 410 300 110 185 270 215 56 165 125 26.4
5/32 5.3 690 490 720 535 195 340 420 370 84 270 215 36
5/32 6.9 1080 770 1130 800 285 575 590 540 114 375 328 46.4
3/16 3.1 290 200 335 215 75 130 210 155 45 125 90 22
3/16 4.4 520 360 550 385 145 250 330 280 68 215 160 30
3/16 5.7 820 560 860 600 220 390 460 410 90 300 244 38.5
3/16 6.9 1120 770 1175 800 285 575 590 540 114 375 328 46.4
3/16 8.1 1600 1000 1720 1100 350 750 725 670 135 480 400 54
1/4 2.3 190 120 210 130 45 75 140 100 32 85 57 16.2
1/4 3.4 340 240 370 250 90 150 230 180 50 140 105 24
1/4 4.3 500 350 540 370 140 230 320 265 66 200 155 29.8
1/4 5.2 690 500 760 510 190 335 410 360 82 265 200 35.4
1/4 6 990 630 1100 660 235 430 530 445 96 340 265 40.5
1/4 7.9 1420 970 1490 1050 340 725 700 650 130 440 390 52.8
3/8 1.6 90 60 95 70 20 40 85 60 21 50 32 11
3/8 2.3 190 120 200 130 45 75 135 100 32 80 57 16.2
3/8 3 285 190 310 200 70 120 200 145 43 125 85 21.2
3/8 3.7 370 270 410 285 105 180 250 200 55 160 115 26
3/8 4.2 520 335 560 355 135 220 310 255 65 200 150 29
3/8 5.4 740 500 800 535 200 360 430 380 86 280 228 36.8
3/8 6.5 950 700 1000 750 265 505 545 500 105 350 300 43.5
5056 1/8 4.5 630 475 690 500 185 320 440 350 70 255 205 28
1/8 6.1 1120 760 1200 825 295 535 690 525 102 400 305 38
1/8 8.1 1750 1200 1900 1300 435 810 945 740 143 560 440 51
5/32 3.8 450 360 500 375 140 235 335 272 57 195 155 24
5/32 5.3 820 615 865 650 240 420 550 435 85 325 250 33
5/32 6.9 1220 920 1340 1000 350 650 760 610 118 430 360 43
3/16 3.1 380 250 410 260 97 170 265 200 45 150 110 20
3/16 4.4 620 460 670 490 180 310 425 340 68 245 198 27
3/16 5.7 920 685 1000 735 270 480 565 480 94 330 280 36
1/4 2.3 240 145 265 155 58 100 180 130 32 100 62 15
1/4 3.4 400 300 480 315 115 200 290 230 50 175 130 22
1/4 4.3 580 440 620 465 172 300 400 325 67 230 190 27
1/4 5.2 790 600 820 645 230 410 490 425 84 300 245 32
3/8 1.6 100 75 110 80 30 50 90 78 20 60 38 10.5
3/8 2.3 215 155 225 155 58 100 170 130 32 95 62 15
3/8 3 320 240 340 260 92 160 245 190 43 145 100 19

Test data obtained at 0.625 inch thickness. I = Beam shear for 12.0 pcf products.

Density Tolerance

The nominal densities of the 5052 and 5056 expanded aluminum honeycomb products are shown in Table 1. The standard density tolerance from the nominal density is ± 10%.

 

Important Properties of Phosphoric Acid Anodized Aluminum Core

Although many tests are used to determine the design properties of aluminum honeycomb, one of the most important properties is how well a honeycomb sandwich structure stands up to its operating environment. In particular, when a sandwich structure is used in a hot/wet environment, it is important to assess the effects of that environment on the performance of the part.

Environmental Peel

For comparison purposes, Hexcel fabricated a number of environmental peel specimens using HexWeb® CR-PAA™ – 3/16 –5052 – .002 – 5.7 (phosphoric add anodized aluminum honeycomb, 3/16 inch cell size, 5.7 pounds per cubic foot core density) and compared them with AMS-C-7438 3/16 – 5052 – .002 – 5.7 core. The sandwich specimen face sheets were perforated on the nonpeel side and hung vertically in a 100% humidity chamber set to 140°F for up to 30 days. After 0, 9, 20, and 30 days, sets of the specimens were removed from the humidity chamber and their residual peel strengths were measured. The results of this comparative testing are shown in the following chart.

Residual peel strengths (in-lb/3 in. width)

During the post test analysis of these specimens, it was observed that the phosphoric acid anodized specimens failed cohesively throughout the 30 days of testing. The AMS-C-7438 cores, on the other hand, began to show evidence of adhesive failure after 9 days in condensing humidity. The observance of such a dramatic difference in the performance of these two core types in this particular environment illustrates how phosphoric acid anodized core extends component part life.

Days Hexcel CR-PAA

AMS-C-7438 Core

0 79.0* 64.7*
9 74.5* 56.8**
20 68.6* 25.6**
30 66.6* 15.8**

* Failure mode = Cohesive
** Failure mode = Adhesive

Acidified Salt Spray Corrosion Testing

Samples of standard AMS-C-7438 core and the phosphoric acid anodized and primed core were exposed to a sulfuric acid salt spray for 5 days and for 10 days. At the end of the exposed period, the samples were cleaned in a special acid and solution that removes corrosion products without attacking the underlying base metal. By weighing the samples before and after acid digestion, the corrosion weight loss could be quantified.

Weight Loss (oz/ft2)

It should be noted that the AMS-C-7438 cores contain a special corrosion-inhibiting compound while the primer on the phosphoric acid anodized core does not. The polymer-based primer on the phosphoric acid anodized core is thicker than the corrosion-resistant coating on the AMS-C-7438 core. The combination of the increased thickness and the integrity of the primer coating contributes to better corrosion resistance of the phosphoric acid anodized core than is inherent with the AMS-C-7438 core. This is significant because the tensile stresses imposed on the primer coating during core expansion have not cracked the specially engineered polymer coating, and its integrity is sufficient to result in excellent corrosion resistance.

Days Hexcel CR-PAA™

AMS-C-7438 Core

5 0.0146 0.0351
15 0.049 0.0825
30 0.0909 0.1113

 

 

Packaging & Availability

Standard Dimensions

Dimensional Nomenclature

HexWeb® CR-PAA - Standard Dimensions

Images for explanation only and do not represent actual appearance.

T = Thickness, or cell depth
L = Ribbon, or longitudinal direction
W = Transverse direction, or direction perpendicular to the ribbon

HexWeb® CR-PAA 5052 and 5056 aluminum honeycomb is available in the following standard size:

Expanded Sheets

L W Nominal Sq.Ft.
48 in. + 3 in. - 0 in. 96 in. + 4 in. - 0 in. 32

Dimensional Tolerances

Tolerances on cut thickness for standard size and smaller sheets are as follows:

Sheet Thickness Standard Tolerances
0.250 in. to 3.999 in. ± 0.005 in.
4.000 in. and over ± 0.062 in.