Quartz glass is frequently assumed to be mechanically weak due to its glassy nature; however, incomplete understanding of its intrinsic mechanical properties often leads to misjudgment, overconservatism, or unexpected failure.
This article consolidates the mechanical properties of quartz glass into a single, coherent material-level framework, addressing strength, elasticity, fracture behavior, and hardness using quantified data and established physical principles.
By progressing from atomic structure to measurable mechanical constants, the discussion establishes how quartz glass behaves as a solid under load, why it exhibits high strength yet low damage tolerance, and how its mechanical parameters should be interpreted without reference to specific applications.
Quartz Glass As A Mechanical Material
From a mechanical perspective, quartz glass occupies a distinct position between crystalline ceramics and conventional glasses, requiring independent treatment rather than analogy-based assumptions. Its amorphous silica network produces mechanical responses that are isotropic, highly elastic, and strongly defect-sensitive, while remaining fundamentally brittle. Consequently, understanding the mechanical properties of quartz glass begins with its atomic structure and extends through its elastic and fracture behavior as a unified material system.
Atomic Bonding And Network Rigidity In Amorphous Silica
Quartz glass consists of a continuous three-dimensional network of Si–O–Si bonds, where each silicon atom is tetrahedrally coordinated with oxygen atoms. Bond energies in this network are high, with Si–O bond strengths typically reported around 450 kJ·mol⁻¹, contributing to substantial stiffness and resistance to elastic deformation.
In experimental mechanical characterization, this rigid covalent network manifests as a high Young’s modulus of approximately 72–74 GPa at room temperature, comparable to some polycrystalline ceramics. Unlike crystalline lattices, however, the absence of long-range periodicity eliminates preferred slip planes, suppressing dislocation-mediated plasticity.
As a result, mechanical loading is accommodated almost entirely through elastic bond stretching and angular distortion. Once local bond strain exceeds critical thresholds, bond rupture occurs without prior plastic relaxation, a defining feature of the mechanical properties of quartz glass.
Isotropic Elastic Behavior In Non Crystalline Solids
Mechanical isotropy is a direct consequence of the random orientation of structural units in amorphous silica. Elastic constants measured along different directions converge within experimental uncertainty, with Poisson’s ratio consistently reported between 0.16 and 0.18 for high-purity fused silica.
Laboratory observations during uniaxial compression and bending tests show uniform lateral contraction and recovery upon unloading, confirming the absence of directional stiffness variations. This isotropy simplifies elastic analysis, as modulus values do not require crystallographic correction factors.
At the same time, isotropy does not imply mechanical uniformity at the microscale. Local variations in bond angle and ring size introduce nanoscale stress heterogeneity, which becomes critical when evaluating fracture initiation. These features collectively define the elastic portion of the mechanical properties of quartz glass.
Mechanical Identity Compared With Crystalline Solids
In crystalline ceramics such as alumina, plastic deformation is limited but not entirely absent due to dislocation activity at elevated stress or temperature. Quartz glass, by contrast, exhibits no measurable yield point under ambient conditions, remaining linear-elastic up to fracture.
Measured elastic strain limits are typically below 0.1 %, after which catastrophic failure occurs. This behavior contrasts with metals and some ceramics that display strain hardening or microplasticity prior to fracture.
Consequently, the mechanical identity of quartz glass is characterized by high stiffness, moderate intrinsic strength, and extremely low fracture tolerance. Treating it as a weakened ceramic or a strengthened conventional glass fails to capture this combination, underscoring the need to evaluate its mechanical properties as a standalone material class.
Implications Of Structural Disorder On Mechanical Performance
Structural disorder in quartz glass plays a dual mechanical role. On one hand, it removes crystallographic weak planes, allowing relatively high compressive and flexural strengths to be achieved under ideal surface conditions. Reported compressive strengths often exceed 1000 MPa in short-duration tests.
On the other hand, disorder amplifies sensitivity to microscopic flaws. Atomic-scale variations accumulate stress around surface defects, scratches, or inclusions, drastically reducing measured tensile and flexural strength. As a result, reported strength values span wide ranges even for nominally identical compositions.
This duality explains why the mechanical properties of quartz glass appear contradictory in literature, described simultaneously as “strong” and “fragile.” The apparent paradox resolves once elastic rigidity, defect sensitivity, and brittle fracture1 are considered as inseparable aspects of the same amorphous network.
Summary Table: Fundamental Mechanical Identity Of Quartz Glass
| Property | Typical Value (Room Temperature) |
|---|---|
| Young’s modulus (GPa) | 72–74 |
| Poisson’s ratio (–) | 0.16–0.18 |
| Elastic strain limit (%) | < 0.1 |
| Plastic deformation | None |
| Mechanical isotropy | High |
Strength Characteristics Of Quartz Glass
Within material mechanics discussions, strength is often interpreted as a fixed constant; however, for brittle amorphous solids such as quartz glass, strength represents a conditional response governed by surface state, flaw population, and loading mode. Consequently, examining strength characteristics requires separating intrinsic bond resistance from extrinsic defect-controlled failure, while maintaining quantitative clarity. Through this lens, the mechanical properties of quartz glass reveal why reported strength values span wide ranges yet remain physically consistent.
Flexural Strength As The Dominant Reported Metric
Flexural strength is the most frequently cited strength parameter for quartz glass because bending tests amplify tensile stresses at the surface, where failure typically initiates. Reported room-temperature flexural strength values for high-purity fused quartz commonly fall between 50 and 120 MPa, depending on surface finish and specimen preparation.
In controlled laboratory conditions using polished specimens, four-point bending tests often yield values near the upper end of this range, whereas as-drawn or lightly machined surfaces exhibit significantly lower results. Experimental records repeatedly show that removing surface micro-scratches can increase measured flexural strength by more than 60%, even though bulk composition remains unchanged.
This sensitivity illustrates a defining aspect of the mechanical properties of quartz glass: flexural strength reflects surface condition rather than bulk atomic bonding. Accordingly, flexural data should be interpreted as an indicator of surface-controlled tensile resistance, not as an intrinsic material constant.
Surface Condition Dependence Of Measured Strength
Surface flaws act as stress concentrators that locally magnify applied tensile stress, accelerating crack initiation. In quartz glass, microscopic surface defects with characteristic sizes of 1–10 μm are sufficient to reduce apparent strength by half under bending or tension.
Observations from fracture surface analysis consistently reveal mirror–mist–hackle patterns, confirming brittle crack propagation from surface-originating flaws. Even optically smooth surfaces retain subsurface damage layers introduced during grinding or handling, which explains why nominally identical specimens produce divergent strength results.
As a consequence, the mechanical properties of quartz glass cannot be decoupled from surface integrity when strength is discussed. Strength values reported without explicit surface condition context represent conditional performance envelopes rather than universal limits.
Tensile Strength And Intrinsic Brittleness
Direct tensile testing of quartz glass is experimentally challenging due to alignment sensitivity and gripping-induced stress concentrations. Nevertheless, available data indicate tensile strength values typically ranging from 30 to 70 MPa for standard laboratory specimens.
In tension, the absence of plastic deformation means that elastic strain accumulates uniformly until a critical flaw reaches unstable crack growth. Measured elastic strain at fracture rarely exceeds 0.05–0.08%, corresponding closely with the elastic modulus and tensile stress limits.
This behavior underscores the intrinsic brittleness embedded within the mechanical properties of quartz glass. Tensile strength does not represent bond strength exhaustion but rather the stress level at which the most severe flaw becomes energetically favorable for crack extension.
Compressive Strength And Atomic Packing Resistance
Under compressive loading, quartz glass exhibits markedly higher strength due to the suppression of crack opening mechanisms. Short-duration compression tests routinely report compressive strengths exceeding 1000 MPa, with some measurements approaching 1500 MPa for defect-minimized specimens.
At the atomic scale, compressive stress shortens Si–O bond lengths and reduces intertetrahedral angles without promoting crack growth. Unlike tensile loading, existing flaws are driven closed rather than opened, delaying catastrophic failure.
Despite these high values, compressive strength is seldom the limiting parameter in practical assessments of the mechanical properties of quartz glass. Instead, tensile and flexural modes dominate failure considerations, reinforcing the asymmetry between compressive and tensile resistance inherent to brittle materials.
Strength As A Statistical Property Rather Than A Constant
Strength measurements for quartz glass consistently follow statistical distributions rather than converging to a single deterministic value. Weibull modulus values reported for fused silica typically range between 5 and 10, indicating moderate scatter compared with crystalline ceramics.
This statistical nature arises because failure initiates at the largest effective flaw within the stressed volume or surface area. Larger specimens or higher stressed surface regions statistically increase the probability of encountering a critical defect, reducing measured strength.
Therefore, within the mechanical properties of quartz glass, strength must be understood as a probabilistic outcome influenced by defect population, test geometry, and stress distribution. Treating strength as a fixed scalar obscures the physical mechanisms governing brittle failure.
Summary Table: Strength Parameters Of Quartz Glass
| Strength Parameter | Typical Range (MPa) |
|---|---|
| Flexural strength | 50–120 |
| Tensile strength | 30–70 |
| Compressive strength | 1000–1500 |
| Elastic strain at fracture (%) | 0.05–0.08 |
| Weibull modulus (–) | 5–10 |
Elastic Properties Of Quartz Glass
Elastic behavior forms the quantitative backbone of material mechanics, linking applied stress to recoverable deformation through well-defined constants. In quartz glass, elastic properties are governed by strong covalent bonding within an amorphous network, producing predictable linear responses up to fracture. Accordingly, elastic constants provide the most stable and reproducible subset of the mechanical properties of quartz glass, supporting calculation, comparison, and interpretation across studies.
Youngs Modulus And Bond Stiffness Interpretation
Young’s modulus of quartz glass reflects the stiffness of the Si–O bond network under uniaxial loading. Experimental measurements consistently report values between 72 and 74 GPa at room temperature, with variation typically within ±2% for high-purity fused silica.
At the atomic scale, elastic deformation corresponds to reversible stretching of Si–O bonds and small angular changes within SiO₄ tetrahedra. Neutron scattering and vibrational spectroscopy studies correlate elastic modulus with bond force constants rather than microstructural features, explaining the narrow data scatter compared with strength values.
In mechanical testing environments, this stiffness produces limited elastic strain before failure. Combining a modulus near 73 GPa with tensile fracture stresses of 30–70 MPa yields elastic strain limits below 0.1%, a defining characteristic within the mechanical properties of quartz glass.
Poissons Ratio And Volume Conservation Behavior
Poisson’s ratio describes lateral contraction under axial loading and provides insight into volumetric deformation mechanisms. For quartz glass, reported Poisson’s ratio values cluster tightly between 0.16 and 0.18, indicating relatively low lateral strain coupling.
Such values suggest that elastic deformation is dominated by bond stretching rather than significant network densification. In comparison, materials with higher Poisson’s ratios exhibit greater shear accommodation and volumetric change, which quartz glass largely resists due to its rigid tetrahedral framework.
Repeated measurements across compression, tension, and bending configurations confirm isotropic Poisson behavior within experimental uncertainty. This consistency reinforces the reliability of Poisson’s ratio as a stable component of the mechanical properties of quartz glass.
Elastic Limit And Absence Of Yield Point
Unlike metals or some crystalline ceramics, quartz glass exhibits no detectable yield point preceding fracture. Stress–strain curves remain linear up to catastrophic failure, with proportionality maintained until bond rupture initiates crack propagation.
Instrumented tensile and bending tests show deviation from linearity only within the final 1–2% of the fracture load, a range often attributed to microcrack activation rather than true plasticity. No permanent strain is observed after unloading below fracture stress, even after repeated cycles.
This absence of yielding means that elastic constants retain their validity across the full usable stress range. Consequently, elastic parameters form the most dependable quantitative elements within the mechanical properties of quartz glass.
Recoverable Deformation And Energy Storage
Elastic energy storage capacity in quartz glass is limited by its low strain tolerance rather than low stiffness. The elastic energy density, approximated by ½·σ·ε, remains modest because fracture intervenes at small elastic strains.
For example, at a tensile stress of 50 MPa and strain of 0.07%, elastic energy density remains below 0.02 MJ·m⁻³, significantly lower than that of ductile metals. This limitation explains why quartz glass cannot dissipate mechanical energy through deformation and instead fails abruptly.
Nevertheless, within its elastic range, deformation is fully recoverable and repeatable. This predictable elasticity, combined with narrow modulus variability, underscores the central role of elastic constants in describing the mechanical properties of quartz glass.
Summary Table: Elastic Properties Of Quartz Glass
| Elastic Property | Typical Value |
|---|---|
| Young’s modulus (GPa) | 72–74 |
| Poisson’s ratio (–) | 0.16–0.18 |
| Elastic strain limit (%) | < 0.1 |
| Yield behavior | None |
| Elastic isotropy | High |
Fracture Behavior Of Quartz Glass
Fracture behavior represents the decisive boundary between elastic integrity and catastrophic failure in brittle solids. For quartz glass, fracture does not emerge gradually through plastic damage accumulation but instead follows well-defined crack mechanics governed by bond rupture and flaw geometry. Accordingly, understanding fracture behavior is essential for interpreting why the mechanical properties of quartz glass combine relatively high strength with exceptionally low tolerance for damage.
Fracture Toughness As A Measure Of Crack Resistance
Fracture toughness quantifies a material’s resistance to crack propagation once a crack has formed. For quartz glass, reported mode I fracture toughness values typically fall within 0.7–0.9 MPa·m¹ᐟ², markedly lower than most polycrystalline ceramics.
At the microscopic level, crack advance in quartz glass involves sequential breaking of Si–O bonds along energetically favorable paths. Because the amorphous network lacks mechanisms such as grain bridging or crack deflection, little additional energy is dissipated during crack growth.
Consequently, even modest tensile stresses can drive rapid crack extension once a critical crack size is reached. This low fracture toughness is a central component of the mechanical properties of quartz glass and explains its pronounced sensitivity to surface and subsurface flaws.
Crack Initiation In Amorphous Networks
Crack initiation in quartz glass almost invariably originates at surface defects rather than within the bulk. Experimental fractography identifies scratches, pits, and machining-induced microcracks with characteristic dimensions of 0.5–5 μm as common initiation sites.
Within these regions, local stress concentration factors can exceed 10× the nominal applied stress, allowing bond rupture to occur far below the theoretical strength of the Si–O network. Once initiated, cracks align with regions of locally weakened bonding or densification heterogeneity.
This behavior highlights a critical distinction within the mechanical properties of quartz glass: intrinsic atomic bonding strength remains high, while effective fracture resistance is dictated by defect geometry and distribution.
Crack Propagation Without Plastic Shielding
In materials capable of plastic deformation, crack tips are blunted through localized yielding, reducing stress intensity. Quartz glass lacks this mechanism entirely. Stress concentration at the crack tip remains sharp, maintaining high stress intensity factors during propagation.
High-speed imaging of crack growth in fused silica reveals propagation velocities approaching 1500–1700 m·s⁻¹, close to the Rayleigh wave speed for the material. Such rapid propagation leaves no opportunity for energy dissipation through microstructural rearrangement.
As a result, fracture proceeds in a nearly ideal brittle manner, reinforcing why fracture toughness, rather than strength alone, dominates failure behavior within the mechanical properties of quartz glass.
Catastrophic Failure And Lack Of Warning Deformation
One of the most consequential aspects of quartz glass fracture is the absence of macroscopic warning prior to failure. Stress–strain measurements remain linear until the instant of fracture, with no detectable deviation signaling impending crack instability.
Recorded strain at failure typically remains below 0.08%, insufficient to generate visible deformation or audible cracking before rupture. This behavior contrasts with tougher ceramics or metals that exhibit microcracking or plastic flow as precursors to failure.
The lack of warning deformation means that fracture in quartz glass is sudden and complete once critical conditions are met. This characteristic defines the ultimate limitation imposed by fracture behavior on the mechanical properties of quartz glass.
Relationship Between Strength And Fracture Toughness
Strength and fracture toughness are often conflated, yet they represent distinct aspects of fracture mechanics. In quartz glass, measured strength reflects the stress required to activate the largest critical flaw, while fracture toughness governs how readily that flaw propagates once activated.
Theoretical fracture mechanics relationships show that critical stress is inversely proportional to the square root of flaw size, scaled by fracture toughness. Given a toughness near 0.8 MPa·m¹ᐟ², even micron-scale flaws substantially reduce allowable stress.
Therefore, high reported flexural or tensile strength values do not contradict low fracture toughness; instead, they coexist within the same framework. Recognizing this relationship is essential for a coherent interpretation of the mechanical properties of quartz glass.
Summary Table: Fracture Properties Of Quartz Glass
| Fracture Property | Typical Value |
|---|---|
| Fracture toughness K_IC (MPa·m¹ᐟ²) | 0.7–0.9 |
| Crack initiation size (μm) | 0.5–5 |
| Crack propagation speed (m·s⁻¹) | 1500–1700 |
| Plastic deformation at crack tip | None |
| Failure mode | Catastrophic brittle fracture |
Hardness Of Quartz Glass
Hardness is frequently cited when discussing glass materials; however, its mechanical meaning differs fundamentally from strength or fracture resistance. In quartz glass, hardness reflects resistance to localized surface deformation rather than load-bearing capability. Clarifying this distinction is essential for correctly interpreting hardness data within the broader mechanical properties of quartz glass.
Vickers And Knoop Hardness Measurement Results
Microindentation testing provides the most widely referenced hardness values for quartz glass. Vickers hardness values typically range from 500 to 650 HV under standard test loads between 0.1 and 1 kgf, while Knoop hardness values are commonly reported between 520 and 600 HK.
During indentation, deformation is confined to a small volume beneath the indenter, where elastic strain accumulates until localized bond rupture occurs. Unlike ductile materials, quartz glass does not exhibit plastic flow around the indent; instead, elastic recovery dominates once the load is removed.
These measurements demonstrate that hardness in quartz glass arises from strong Si–O bonding rather than from dislocation-mediated resistance. Accordingly, microhardness values represent surface-scale resistance and form a distinct subset of the mechanical properties of quartz glass.
Mohs Hardness And Relative Scratch Resistance
On the Mohs scale, quartz glass is generally assigned a hardness of approximately 6–7, comparable to crystalline quartz. This classification reflects its resistance to scratching by common minerals rather than its response to applied mechanical stress.
Scratch testing observations show that surface damage initiates when the applied contact stress exceeds local bond strength, producing microcracks rather than grooves formed by plastic flow. The onset of visible scratching often corresponds to contact stresses above 7–9 GPa, depending on indenter geometry.
Thus, Mohs hardness offers qualitative insight into abrasion and scratch resistance but provides no direct information about tensile strength or fracture behavior. Within the mechanical properties of quartz glass, Mohs hardness serves as a comparative surface metric rather than a structural parameter.
Hardness As A Surface Property
Hardness measurements probe only a shallow surface layer, typically within 1–5 μm of the surface for common microindentation loads. As a result, hardness values are strongly influenced by surface preparation, residual damage, and contamination.
Polished surfaces consistently yield higher and more reproducible hardness values than ground or as-formed surfaces. Experimental comparisons demonstrate variations of up to 15% in measured hardness due solely to surface finish, even when bulk composition remains identical.
This surface sensitivity reinforces the principle that hardness, while useful, reflects localized mechanical response rather than bulk material behavior. Interpreting hardness without acknowledging its surface dependence can misrepresent the true mechanical properties of quartz glass.
Why High Hardness Does Not Imply High Toughness
A common misconception equates high hardness with superior mechanical robustness. In quartz glass, this assumption fails because hardness and fracture toughness describe fundamentally different phenomena.
Despite Vickers hardness values exceeding 500 HV, fracture toughness remains low at approximately 0.7–0.9 MPa·m¹ᐟ². Indentation-induced radial cracks often form around hardness impressions, visually demonstrating that resistance to indentation does not prevent crack initiation or propagation.
This contrast highlights a central theme within the mechanical properties of quartz glass: strong atomic bonding confers hardness and stiffness, while the absence of plastic deformation limits damage tolerance. Recognizing this divergence is essential for a coherent understanding of quartz glass mechanics.
Summary Table: Hardness Characteristics Of Quartz Glass
| Hardness Metric | Typical Range |
|---|---|
| Vickers hardness HV | 500–650 |
| Knoop hardness HK | 520–600 |
| Mohs hardness | 6–7 |
| Indentation depth (μm) | 1–5 |
| Relation to fracture toughness | No direct correlation |
Interrelation Among Mechanical Properties Of Quartz Glass
Across experimental observations, individual mechanical parameters rarely act in isolation; instead, elastic stiffness, strength, hardness, and fracture resistance interact to define overall mechanical behavior. Recognizing these interactions clarifies why quartz glass exhibits seemingly contradictory characteristics under load. Through integrated interpretation, the mechanical properties of quartz glass emerge as a coherent and internally consistent material system.
Elastic Modulus And Strength Correlation Limits
Elastic modulus and strength are often assumed to scale together; however, quartz glass demonstrates clear limits to this assumption. With a Young’s modulus consistently near 72–74 GPa, stiffness remains stable across specimens, while tensile and flexural strength vary widely from 30 to 120 MPa depending on surface condition.
This divergence arises because elastic modulus reflects average bond stiffness throughout the bulk, whereas strength is governed by the largest effective flaw. Experimental datasets show that specimens with identical modulus values can fail at stresses differing by more than 2×, underscoring the decoupling between stiffness and failure stress.
Accordingly, within the mechanical properties of quartz glass, elastic modulus defines deformation response but provides little predictive power for fracture stress without complementary flaw information.
Hardness Versus Fracture Resistance Tradeoffs
Hardness measurements indicate resistance to localized surface deformation, yet they do not scale with fracture resistance in quartz glass. Vickers hardness values exceeding 500 HV coexist with fracture toughness values limited to 0.7–0.9 MPa·m¹ᐟ², a combination rarely observed in tougher ceramics.
Indentation experiments frequently reveal radial and median cracking around hardness impressions, even when permanent indentation depths remain shallow. These cracks demonstrate that high contact stress resistance does not equate to energy dissipation capability during crack growth.
This tradeoff illustrates a critical interrelation: strong atomic bonding elevates hardness and stiffness, while the absence of plastic accommodation suppresses fracture toughness. Both attributes coexist as complementary aspects of the mechanical properties of quartz glass.
Why Quartz Glass Is Strong Yet Fragile
The phrase “strong yet fragile” captures a fundamental paradox resolved by fracture mechanics. Under ideal conditions, quartz glass can sustain flexural stresses above 100 MPa, indicating significant resistance to elastic loading.
However, once a critical flaw reaches the Griffith criterion2, crack propagation proceeds with minimal resistance. Given fracture toughness below 1 MPa·m¹ᐟ², even micron-scale defects become dominant, rapidly converting stored elastic energy into fracture surface energy.
Thus, strength reflects the stress required to activate a flaw, while fragility reflects the ease of crack propagation thereafter. This duality is central to the mechanical properties of quartz glass and distinguishes it from both ductile solids and tougher ceramics.
Mechanical Property Balance In Amorphous Silica
When considered collectively, the mechanical properties of quartz glass form a balanced yet constrained profile. High stiffness ensures dimensional stability under load, while moderate intrinsic strength allows limited elastic stress accommodation.
Simultaneously, low fracture toughness and minimal strain capacity restrict tolerance for defects and overload. Experimental correlations consistently show that improvements in apparent strength through surface refinement do not alter elastic constants or intrinsic fracture resistance.
This balance defines quartz glass as a material optimized for elastic precision rather than damage tolerance. Understanding the interrelation among its mechanical parameters enables accurate interpretation without attributing contradictory meanings to individual values.
Summary Table: Interrelation Of Mechanical Properties In Quartz Glass
| Property Pair | Observed Relationship |
|---|---|
| Elastic modulus vs strength | Weak correlation |
| Hardness vs fracture toughness | Inversely related behavior |
| Strength vs flaw size | Strong inverse dependence |
| Elastic strain vs toughness | Both remain low |
| Overall mechanical character | Stiff and brittle |
Summary Of Mechanical Properties Of Quartz Glass
Quartz glass exhibits a mechanically consistent yet highly constrained profile defined by strong covalent bonding and an amorphous atomic network. Elastic stiffness remains stable and reproducible, while strength and failure behavior are governed by surface flaws and crack mechanics rather than intrinsic bond weakness. As a result, quartz glass combines high stiffness and hardness with low fracture tolerance, leading to abrupt brittle failure once critical conditions are reached.
From a material mechanics standpoint, the mechanical properties of quartz glass must be interpreted as an integrated system. Elastic constants describe predictable deformation, strength values reflect statistical defect control, hardness represents localized surface resistance, and fracture toughness defines the ultimate limit of damage tolerance. Evaluating these parameters together provides a complete and accurate understanding of quartz glass as a mechanical material.
Summary Table: Mechanical Properties Of Quartz Glass
| Mechanical Parameter | Typical Range Or Value | Unit |
|---|---|---|
| Young’s modulus | 72–74 | GPa |
| Poisson’s ratio | 0.16–0.18 | – |
| Elastic strain limit | < 0.1 | % |
| Flexural strength | 50–120 | MPa |
| Tensile strength | 30–70 | MPa |
| Compressive strength | 1000–1500 | MPa |
| Fracture toughness (K_IC) | 0.7–0.9 | MPa·m¹ᐟ² |
| Vickers hardness | 500–650 | HV |
| Knoop hardness | 520–600 | HK |
| Mohs hardness | 6–7 | – |
| Dominant failure mode | Brittle catastrophic fracture | – |
| Plastic deformation | None | – |
Conclusion
Quartz glass exhibits a unique mechanical identity defined by high elastic stiffness, limited strain capacity, and brittle fracture governed by flaw-controlled mechanics. Elastic constants remain stable and reproducible, while strength and failure reflect statistical defect effects rather than bond weakness. Understanding the mechanical properties of quartz glass requires integrating elasticity, strength, hardness, and fracture toughness into a single cohesive material framework rather than evaluating each parameter in isolation.
FAQ
Is quartz glass mechanically strong compared with other glasses?
Quartz glass shows higher stiffness and compressive strength than many common glasses, but tensile and flexural strength remain highly dependent on surface condition and flaw population.
Why does quartz glass fail without visible deformation?
Failure occurs once elastic strain reaches the fracture threshold, as no plastic deformation mechanisms exist to provide warning or energy dissipation.
Does high hardness mean quartz glass is damage resistant?
High hardness indicates resistance to local indentation and scratching, but fracture toughness remains low, allowing cracks to propagate readily once initiated.
Are mechanical properties of quartz glass isotropic?
Yes. The amorphous structure produces nearly identical elastic and strength responses in all directions within experimental uncertainty.
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