Composite Laminate Toughened Interlayer Crack Resistance

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Solution Overview

Problem

Composite laminates are prone to crack initiation and propagation due to impacts, particularly mode I, mode II, and mode III cracks, which existing interlayers with thermoplastic spheres or resin fail to effectively impede.

Innovation Solution

Incorporating toughened regions within the interlayer that extend between and are fused to the fiber beds, enhancing the laminate's resistance to crack propagation by mechanically interlocking or bonding with the fiber beds, thereby improving interlaminar toughness and impact properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional interlayers with thermoplastic spheres or resin are used, then the laminate structure is maintained, but the propagation of mode I, mode II and mode III cracks is not effectively impeded

Engineering Contradiction:

Improvecrack propagation resistanceVSAvoidinterlayer structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The interlayer is segmented into discrete toughened regions distributed between fiber beds, rather than using a continuous traditional interlayer material. These segmented regions provide crack propagation resistance while maintaining structural integrity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The interlayer combines thermoplastic material with a support structure to create a composite toughened region. This composite structure provides both the toughness needed to impede cracks and the structural support required for laminate integrity.

Inventive Principle:

Principle #40Composite materials

2Reliability

If toughened regions are added to impede crack propagation, then crack resistance improves, but the manufacturing process becomes more complex

Engineering Contradiction:

Improveinterlaminar toughnessVSAvoidfabrication process simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The support structure for the toughened regions is prepared in advance before final assembly. This preliminary preparation of the support structure simplifies the overall manufacturing process by allowing components to be pre-fabricated and then assembled.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces traditional mechanical bonding methods with fusion bonding of thermoplastic material. The thermoplastic is heated to melt and fuse the toughened regions to the fiber beds, eliminating complex mechanical fastening systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If thermoplastic material is used in the interlayer, then crack propagation is impeded, but the thermoplastic may not adequately bond to the fiber beds

Engineering Contradiction:

Improvecrack propagation resistanceVSAvoidbond strength between interlayer and fiber beds

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

A support structure acts as an intermediary between the thermoplastic toughened regions and the fiber beds. This intermediary facilitates adequate bonding and mechanical interlocking, ensuring both crack resistance and strong attachment to the fiber beds.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The fusion of toughened regions to the fiber beds significantly impedes the propagation of in-plane mode I and mode II cracks, enhancing the composite laminate's toughness and impact resistance.

Implementation Method 1

heating the stack to a temperature sufficient to melt the thermoplastic material

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

fusing a plurality of thermoplastic regions of an interlayer to adjacent dry fiber beds

Methodology Applied

Scientific EffectFusion: Welding

Data Source

PatentUS9821530B2Composite laminate including interlayers with through-plane regions fused to fiber beds

Publication Date: 2017.11.21 THE BOEING CO

AI summary

A composite laminate comprises first and second fiber beds, and an interlayer between the fiber beds. The interlayer includes toughened regions that extend between the fiber beds and are fused to the fiber beds.