Short answer
When designing with composites, prioritize manufacturing processes that apply vacuum or pressure (like vacuum bagging) to minimize voids, especially for parts under shear stress.
- Field
- Final Production
- Source
- Journal of Composite Materials (2018)
- Method
- Literature Review and Meta-analysis
- Sample
- Meta-analysis of over 50 years of research papers
- Evidence
- Strong effect
Manufacturing defects known as voids significantly degrade the mechanical performance of composites by acting as stress concentrators and facilitating crack propagation. This final production research insight is drawn from a 2018 study published in Journal of Composite Materials. Using Literature review and meta-analysis with Meta-analysis of over 50 years of research papers, researchers explored how this design variable affects real-world outcomes. The key design takeaway: When designing with composites, prioritize manufacturing processes that apply vacuum or pressure (like vacuum bagging) to minimize voids, especially for parts under shear stress.
A 1% increase in void content reduces interlaminar shear strength by up to 10% in fiber-reinforced composites
Manufacturing defects known as voids significantly degrade the mechanical performance of composites by acting as stress concentrators and facilitating crack propagation.
Journal of Composite Materials · 2018
Key Findings
- 01Voids are primarily formed by entrapped air, moisture, or volatiles during the resin infusion or curing stages.
- 02Interlaminar shear strength (ILSS) is the property most sensitive to voids, often dropping 7-10% for every 1% of void volume.
- 03Matrix-dominated properties (compression, fatigue life) are more affected by voids than fiber-dominated properties (tension).
- 04Modern 'out-of-autoclave' manufacturing increases the risk of void formation compared to traditional high-pressure methods.
Application
Design takeaway
When designing with composites, prioritize manufacturing processes that apply vacuum or pressure (like vacuum bagging) to minimize voids, especially for parts under shear stress.
How to apply
Use vacuum-assisted resin transfer molding (VARTM) and ensure proper degassing of resins before application to maintain structural integrity.
Project actions
- 01If making a composite part for your project, use a vacuum bag to show you are 'optimizing manufacturing' to reduce voids.
- 02Mention 'interlaminar shear strength' when discussing why your composite test samples might have failed earlier than expected.
Method & Evidence
Variables
Strengths & Limitations
Strengths
- +Comprehensive review of 50 years of data
- +Links microscopic defects to macroscopic failure
Limitations
Students usually lack the 'CT scanning' equipment mentioned in the paper to actually measure the exact percentage of voids in their IA models.
Reliability & validity
High reliability due to the meta-analysis approach; high validity for industrial applications but may vary with student-grade resins.
Think critically
If voids are so damaging, why do some industries accept a 'void limit' (e.g., 1-2%) instead of demanding 0% voids in every part?
Design Principles
"The Strength-to-Void Ratio: Mechanical reliability in composites is inversely proportional to the volume of entrapped gas during the curing phase."
In design, understanding material properties and manufacturing defects is crucial for design topics. This research highlights how production variables like resin viscosity and curing pressure directly impact the structural integrity and reliability of high-performance composite products.
What This Means for Your Design
Tiny air bubbles trapped inside carbon fiber or fiberglass act like 'holes' that make the material snap much easier than it should, especially when the layers try to slide past each other.
How to use in your project
- 1.Cite this to justify why you chose a specific layup technique or why you used a vacuum pump during your prototype fabrication.
Add to My Project
Quick Cite
Paragraph starter
According to Mehdikhani et al. (2018), voids are critical manufacturing defects in composites that significantly reduce interlaminar shear strength. This research suggests that even a 1% increase in void content can lead to a 10% reduction in strength, justifying the use of vacuum-assisted curing in this project to ensure structural integrity.
Source
Journal of Composite Materials
Voids in fiber-reinforced polymer composites: A review on their formation, characteristics, and effects on mechanical performance
journal · 2018
View sourceQuestions About This Research
- What does the research say about a 1% increase in void content reduces interlaminar shear strength by up to 10% in fiber-reinforced composites?
- When designing with composites, prioritize manufacturing processes that apply vacuum or pressure (like vacuum bagging) to minimize voids, especially for parts under shear stress. Evidence: Journal of Composite Materials (2018).
- Why does "A 1% increase in void content reduces interlaminar shear strength by up to 10% in fiber-reinforced composites" matter for design?
- In IB DT, understanding material properties and manufacturing defects is crucial for Topic 4. This research highlights how production variables like resin viscosity and curing pressure directly impact the structural integrity and reliability of high-performance composite products.
- How can designers apply this research?
- When designing with composites, prioritize manufacturing processes that apply vacuum or pressure (like vacuum bagging) to minimize voids, especially for parts under shear stress.
- What were the main findings?
- Voids are primarily formed by entrapped air, moisture, or volatiles during the resin infusion or curing stages.. Interlaminar shear strength (ILSS) is the property most sensitive to voids, often dropping 7-10% for every 1% of void volume.. Matrix-dominated properties (compression, fatigue life) are more affected by voids than fiber-dominated properties (tension).. Modern 'out-of-autoclave' manufacturing increases the risk of void formation compared to traditional high-pressure methods.
- What research method was used?
- Literature Review and Meta-analysis with Meta-analysis of over 50 years of research papers.
- How strong is the evidence?
- Evidence strength is rated Strong effect, based on a 2018 journal from Journal of Composite Materials.
- What should I do differently in my next project?
- Use vacuum-assisted resin transfer molding (VARTM) and ensure proper degassing of resins before application to maintain structural integrity.
- What are the limitations?
- The effect of void shape and distribution is harder to quantify than total void volume; complex geometries make void suppression significantly more difficult.