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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. Core Options. Final Core Material. HT Diab 61 - Wing Skins Ability to lay up curves of Airfoils
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Composite Panels • Panels are fiberglass on both sides with a core in the middle consisting of either foam or a honeycomb structure
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
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.) • 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:
Adhesive Testing (Cont.) • Shear Test Top View: (Load Pulling out from picture)
Adhesive Testing (Cont.) • Shear Test:
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]