Viscoelastic Drop-Weight Fixture for Accurate Composite Damage Testing

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Solution Overview

Problem

Current coupon-level tests for damage tolerance in composite materials are overly conservative and do not accurately represent the damage observed in actual structures, leading to significant weight penalties and resource inefficiencies in structural sizing.

Innovation Solution

A test fixture with adjustable viscoelastic elements, including springs and dampers, is used to replicate the boundary conditions of configured panels, allowing for a more accurate assessment of damage tolerance in composite specimens.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If coupon-level tests are used to assess damage tolerance, then testing time and resources are reduced, but the test results become overly conservative and do not accurately represent actual structure performance

Engineering Contradiction:

Improvetesting efficiencyVSAvoiddamage tolerance assessment accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent creates a simplified copy of the configured panel boundary conditions using viscoelastic elements and a drop-weight impactor on a coupon specimen. This copying approach allows coupon-level testing to replicate the essential mechanical behavior of full-scale panels, maintaining measurement accuracy while improving testing efficiency.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent modifies the test parameters by introducing viscoelastic elements with specific damping characteristics and controlling the drop-weight impact parameters (mass, height, impactor geometry). These parameter changes enable the coupon test to capture the energy dissipation and boundary condition effects that previously required full panel testing.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If configured panel tests are performed to accurately assess damage tolerance, then measurement accuracy is improved, but testing time and resources are substantially consumed

Engineering Contradiction:

Improvedamage tolerance assessment accuracyVSAvoidtesting time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

Instead of testing full configured panels, the patent creates a simplified copy of the boundary conditions using viscoelastic elements attached to a small coupon specimen. This copying approach captures the essential mechanical behavior with minimal specimen size, dramatically reducing testing time while maintaining accuracy.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent segments the complex panel test into a simplified coupon test with representative boundary conditions. By isolating the critical damage tolerance assessment from the full panel complexity, the test can be performed quickly on small specimens while still providing accurate results for structural sizing.

Inventive Principle:

Principle #1Segmentation

3Productivity

If coupon-level testing is used for structural sizing, then productivity is improved, but the structure must be oversized to account for conservatism, increasing weight

Engineering Contradiction:

Improvedesign efficiencyVSAvoidstructural weight

Core Design Contradiction:

ProductivityVSWeight of moving object

Solution Approach 1:

The patent creates an accurate copy of panel-level damage tolerance behavior through coupon testing with viscoelastic boundary conditions. This eliminates the need for conservative oversizing, allowing structures to be optimized for minimum weight while maintaining safety margins based on accurate test data.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

By changing the test parameters to include viscoelastic elements that replicate panel boundary conditions, the patent produces accurate damage tolerance data that can be directly used for structural sizing. This eliminates the conservatism that previously led to oversized, heavier structures.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables improved structural testing that reduces conservatism in allowable damage, allowing for lighter and more efficient structural designs without the need for extensive configured panel testing.

Implementation Method 1

a plurality of viscoelastic elements; wherein the plurality of specimen clamping elements are secured to the base via the plurality of viscoelastic elements

Methodology Applied

Scientific EffectViscoelasticity: Viscoelasticity

Implementation Method 2

one of the plurality of viscoelastic elements being a spring and a damper; wherein the spring is an adjustable spring having a selectable spring constant

Methodology Applied

Scientific EffectSpring elasticity: Spring

Implementation Method 3

wherein the damper is an adjustable damper having a selectable damping constant

Methodology Applied

Scientific EffectDamping: Damping

Data Source

PatentUS20260029299A1Test fixture for drop-weight impact event

Publication Date: 2026.01.29 THE BOEING CO

AI summary

A test fixture and associated method are described. The test fixture includes a base defining an aperture; a plurality of specimen clamping elements; and a plurality of viscoelastic elements. The plurality of specimen clamping elements are secured to the base via the plurality of viscoelastic elements. The plurality of specimen clamping elements are arranged to secure a composite specimen to the base and overtop of the aperture.