Composite Panels& Adhesives

Composite Panels

• Panels are fiberglass on both sides with a core in the middle consisting of either foam or a honeycomb structure

Fiberglass Core: Foam or Aramid

Core Options

Material Density

Compresive Strength

Tensile strength

Shear Sength

Shear Modulus

Cost

units (lb/ft^3) psi psi psi psi ($/ft^3)

Cirrus - HT 61 4.1 145 261 131 2900 4.96

Evonik 51 A - PMI Foam 3.248 131 276 116 2760 -

Ultracor UCF-83-1/4-3.0 3 246 27 223 61000

Aramid Core .25 In. Thick 1.8 109 - 52/62 (L/W)1579/2882

(L/W)7.95

Aramid Core .125 In. Thick 1.8 109 - 52/62 (L/W)1579/2882

(L/W)4.95

Final Core Material

• HT Diab 61- Wing Skins

• Ability to lay up curves of Airfoils

• Cheapest that met criteria of foams

• Aramid Core- Spar, Aft Spar, Rib

• Light Weight

• Cheapest per Pound

Adhesive Options• DP 420

– 3M, Two Part Epoxy » From 3M Epoxy Comparison

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Adhesive Options (Cont.)

• PTM & W: – ES6292 Lightweight Tough Epoxy Adhesive

• Two Part Epoxy

• Designed for use in the structural assemblies involving composites

• Already used by Cirrus Design Center

Adhesive Testing

• Objectives:– Test Max Adhesive Loads

• Need to make sure adhesives aren’t effected by surfaces

– Test surface preparation techniques

Adhesive Testing (Cont.)

• Materials Tested:– Adhesives:

• PTM & W ES6292

• 3M DP 420

– Composites:• Aramid Core with Fiberglass Skin

• HT Diab Foam Core with Tencate Fiberglass

Adhesive Testing (Cont.)

• Tensile Test:– Load Bonds in Tension– Measure Load at Fracture– Calculate Lbs/In. Bond Strength

• Test Equipment:– Constant Strain Load Cell– Measures Load and displacement

Adhesive Testing (Cont.)

Adhesive Testing (Cont.)

• Tensile Load Justification:– Jaws:

• 2° freedom on both directions– Top & Bottom

• All samples were applied within 1 degree of perpendicular

• Therefore: Tension loads were perpendicular to bond

Adhesive Testing (Cont.)

• Surface Preparation:– All surfaces were lightly sanded to rough up

surface

– All surfaces were cleaned with to remove

Adhesive Testing (Cont.)

• Results:– Bond Strength per Inch of Bond (Lbs/In)

• PTM & W ES6292= 81.7 ± 4.1 Lbs/In

• 3M DP 420=87.1 ± 4.4 Lbs/In

» Uncertainty Estimated at 5%

Adhesive Testing (Cont.)

• Conclusions:– Adhesives were comparable in

Strength per Inch

– Both Adhesives meet strength requirements for wing

– PTM & W ES6292 Adhesive is better because of lower cost

Adhesive Testing (Cont.)

• Errors:– Improper preparation:

• Issue: Samples broke at surface

• Resolution: Better Surface Preparation– Sanding (possibly Sand Blasting)

– Better Removal of oils from surface

• Effect:– Bonds Broke Prematurely– With Better Preparation Bonds could hold more Weight

Adhesive Testing (Cont.)

– Test Equipment:• Issue: Jaws Slipping• Resolution: Better Transition from Material to Jaw

– Adhere Aluminum Tab into Composite– External Clamp System with Aluminum Tab for Jaw

» Allow Material to be secured by clamp and Jaw to attach to Aluminum Tab

• Effect:– Load might be underestimated. – Result: Bond Strength could be higher than reported

Adhesive Testing (Cont.)

• Further Testing:– Shear Test Side View:

Composite A

Composite B

Adhesive Testing (Cont.)

– Shear Test Top View:(Load Pulling out from picture)

Composite A

Composite B

Bond

Adhesive Testing (Cont.)

• Shear Test:

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Epoxy Safety Precautions

• Effects of Overexposure:– Eyes: Causes severe conjunctive irritation,

Corneal injury and Iritis– Skin: May cause irritation, burns, ulceration, or

skin sensitization– Inhalation: Vapors are irritating and cause tears,

burning of nose and throat, coughing, wheezing nausea and vomiting

Epoxy Safety Precautions (Cont)

– Ingestion: Moderately toxic, may cause mouth and throat burns, abdominal pain, weakness, thirst and coma.

– Chronic: Amine vapors may cause liver and kidney injury. Eye, skin or lung may develop or be irritated by Amine vapors.

[From MSDS of ES6292B with Beads]

Epoxy Handling Precautions

• Respiratory: – Not required unless process is creating dust,

mist or vapor.

• Ventilation: – Breathing of vapor must be avoided.

• Hand Protection:– Impervious gloves, neoprene or rubber, must be

worn

Epoxy Handling Precautions(Cont.)

• Eye Protection:– Splash proof Goggles or safety glasses

• Other:– Clean body covering clothing and shoes

[From MSDS of ES6292B with Beads]

Aramid Core Handling Requirements

• Ventilation required when machining produces dust, mist or vapor

• Light Hand Cotton gloves for General Protection

[From Aramid Core MSDS]