Interlaminar Thermoset Particles for Delamination-Resistant Composites
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Solution Overview
Problem
Fiber-reinforced polymer composites used in aerospace structures face issues with delamination, micro-cracking, and poor interlaminar toughness due to mismatch in thermal expansion coefficients between thermoplastic toughening particles and the thermoset matrix, leading to de-bonding and reduced fracture toughness.
Innovation Solution
Incorporation of chemically active thermoset particles with unreacted functional groups into the interlaminar regions of composite laminates, which form covalent bonds with the resin matrix, reducing thermal expansion mismatch and enhancing interlaminar toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermoplastic toughening particles are incorporated into the interlaminar regions, then interlaminar toughness is improved, but thermal expansion mismatch causes de-bonding and micro-cracking
Solution Approach 1:
The patent changes the chemical and physical parameters of the toughening particles by using chemically active thermoset particles instead of conventional thermoplastic particles. These particles have unreacted functional groups that can form covalent bonds with the resin matrix, and their thermal expansion coefficients are matched to the matrix through chemical composition adjustment, thereby resolving the de-bonding issue while maintaining interlaminar toughness enhancement
Solution Approach 2:
The patent creates a composite particle system where chemically active thermoset particles with specific functional groups are integrated into the thermoset resin matrix. This composite approach allows the particles to both toughen the interlaminar regions and chemically bond with the matrix, eliminating the thermal expansion mismatch problem that plagues conventional thermoplastic particle systems
2Strength
If conventional thermoplastic particles are used for toughening, then delamination resistance is improved, but coefficient of thermal expansion mismatch leads to micro-cracking
Solution Approach 1:
The patent modifies the thermal and chemical parameters of the toughening particles by selecting thermoset particles with adjustable composition. The chemical composition is tailored to match the thermal expansion coefficient of the resin matrix, eliminating the thermal stress that causes micro-cracking during thermal cycling, while the particles continue to provide delamination resistance through their interlaminar positioning and toughness-enhancing properties
Solution Approach 2:
The patent converts the potential harm of thermal expansion mismatch into a benefit by using the chemical reactivity of thermoset particles. The unreacted functional groups on the particle surfaces form covalent bonds with the matrix, creating a strong chemical connection that compensates for and eliminates the thermal expansion differential, thereby preventing micro-cracking while maintaining the particles' beneficial toughening effect
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 use of chemically active thermoset particles improves the composite's resistance to delamination and micro-cracking, increasing Compression Strength After Impact (CAI) and fracture toughness without causing thermal de-bonding, thereby enhancing structural integrity.
Implementation Method 1
Incorporation of chemically active thermoset particles with unreacted functional groups into the interlaminar regions of composite laminates, which form covalent bonds with the resin matrix
Implementation Method 2
mismatch in thermal expansion coefficients between thermoplastic toughening particles and the thermoset matrix, leading to de-bonding
Data Source
Figure 1~2
AI summary
A fiber-reinforced polymeric composite structure having chemically active thermoset particles positioned in an interlaminar region between adjacent layers of reinforcement fibers and method of making the same. Upon curing of the composite structure, the chemically active functional groups on the thermoset particles form covalent bonds with the matrix resin surrounding the particles. In one embodiment, the particles are formed of a partially cured thermoset polymer with a degree of cure of less than 100%. In another embodiment, the particles are derived from a thermosettable resin composition, wherein the stoichiometry is such that there is a deficiency or an excess in the amount of curing agent that is necessary for reacting with 100% of the thermoset resin component. In some embodiments, the composition of the chemically active thermoset particles is the same or substantially the same as that of the matrix resin of the composite structure.